Graduate School Form 9(Revised 10107)

PURDUE UNIVERSITYGRADUATE SCHOOL

ThesislDissertation Acceptance

This is to certify that the thesis/dissertation prepared

By Andrea F. Currylow

Entitled Effects of Forest Management on the Ecology and Behavior of Eastern Box Turtles

For the degree of Master of Science

is not to be regarded as confidential.

To the best ofmy knowledge and as understood by the student in the Research Integrity andCopyright Disclaimer (Graduate School Form 20), this thesis/dissertation adheres to the provisions ofPurdue University's "Policy on Integrity in Research" and the use ofcoX

~ //"orp~,--D is

This thesis [Z]Major Professor

-~~2h~~:;::::==--- or --::---c::--:-::--,..,....,..---xamining Committee Department Thesis Fonnat Advisor

EFFECTS OF FOREST MANAGEMENT ON THE ECOLOGY AND BEHAVIOR OF

EASTERN BOX TURTLES

A Thesis

Submitted to the Faculty

of

Purdue University

by

Andrea F. Currylow

In Partial Fulfillment of the

Requirements for the Degree

of

Master of Science

May 2011

Purdue University

West Lafayette, Indiana

ii

ACKNOWLEDGEMENTS

I thank my graduate committee, Dr. Patrick Zollner and Brian MacGowan, for

considerate direction both in the field and academically as well as offering many detailed

and helpful reviews of manuscripts. I especially thank Dr. Rod Williams, my major

advisor, for affording me the opportunity to work on and develop this project. He has

also been gracious enough to support my pursuits of additional projects stemming from

this one. I am grateful to him for being so thoughtful and helpful as an advisor and

sometimes, a therapist. I would also like to thank the graduate students in PFEN G004

who through sharing office space and coffee breaks, offered help through every issue and

all the questions, but most importantly, offered friendship. For all this, I will always be

grateful.

I would like to thank my loving parents, Gary and Fran Curry, who have always been

there for me with support and inspiration. My fiancée, Michael Tift, deserves many

thanks for enduring the struggles with me as we both undertook the challenges of

graduate school nearly an entire continent apart.

Finally, I would like to thank the changing members of Williams’ lab group and

multitude of field technicians who, without them, none of this could have been possible.

Thank you for your hard work and, for many of you, your friendship.

iii

TABLE OF CONTENTS

Page

LIST OF TABLES ...............................................................................................................v 

LIST OF FIGURES ........................................................................................................... vi 

ABSTRACT ..................................................................................................................... viii 

CHAPTER 1: SHORT-TERM FOREST MANAGEMENT EFFECTS ON A LONG-LIVED ECTOTHERM ....................................................................................................1 

Abstract .......................................................................................................................1 Introduction .................................................................................................................2 Methods.......................................................................................................................4 

Study Area ............................................................................................................4 Forest Management Design and Sampling ...........................................................4 Landscape-Scale Analyses ....................................................................................6 Local-Scale Analyses ............................................................................................8 

Results .........................................................................................................................9 Landscape-Scale Effects .......................................................................................9 Local-Scale Effects .............................................................................................11 

Discussion .................................................................................................................12 Landscape-Scale Effects – home ranges and thermal ecology ...........................13 Local-Scale Effects – movement and edge effects .............................................15 Conservation Implications ..................................................................................17 

Acknowledgements ...................................................................................................17 Literature Cited .........................................................................................................19 Appendix 1 ................................................................................................................35 

CHAPTER 2: HIBERNAL THERMAL ECOLOGY OF EASTERN BOX TURTLES WITHIN A MANAGED FOREST LANDSCAPE .......................................................36 

Abstract .....................................................................................................................36 Introduction ...............................................................................................................37 

Study Area ..........................................................................................................39 Methods.....................................................................................................................40 

Turtle Monitoring................................................................................................40 Experimental Design and Habitat Monitoring ....................................................40 

iv

Page Analyses ..............................................................................................................41 

Results .......................................................................................................................42 Box Turtle Thermal Behavior .............................................................................43 Microclimates of Forests vs. Clearcuts ...............................................................45 

Discussion .................................................................................................................46 Management Implications ...................................................................................50 

Acknowledgements ...................................................................................................50 Literature Cited .........................................................................................................51 Appendix 2 ................................................................................................................63 Appendix 3 ................................................................................................................65 Appendix 4 ................................................................................................................68 

PUBLICATION .................................................................................................................70 

v

LIST OF TABLES

Table Page

Table 1. Pre-harvest (Pre-harv.; 2007-2008) and post-harvest (Post-harv.; 2009-2010) home ranges of female and male Eastern Box Turtles. The associated management class (Mngmnt Class) is listed and home ranges were calculated by biennial Minimum Convex Polygons (MCP) and 95% kernel isopleths. Only the 95% kernel isopleths areas are listed here, as they are the only relevant comparisons to 100% MCP. ................................................................................................................27 

Table 2. Least Squares Means (LS Mean) Tukey-Kramer post-hoc pairwise comparisons connecting letters report of monthly environmental temperatures (Tmin, Tmax, Tmean) during 2009-2010 within four habitat types (clearcut openings, group selection openings, harvest-adjacent forest, and forested control). Habitat types at each level not connected by the same letter are significantly different. .....................................................................................................................28 

Table 3. Published studies involving home range estimates from native populations of T. carolina. .................................................................................................................33 

Table 4. Number and location of temperature dataloggers in harvest openings (H) and forested habitats (F). Slope aspect (NW, SE, etc.) represents the slope for which the logger was assigned or that the overwintering turtle chose. .................................56 

Table 5. Mean body temperatures (Tb) and standard errors for all turtles at hibernation (Hib) and emergence (Emerg). “Unknown” slopes indicate turtles did not select hibernacula by the final tracking date. The 12 turtles associated with hibernaculum Thermal Profile Stakes. ..............................................................................................57 

Table 6. Mean Thermal Profile Stake temperatures (°C) and standard error from all depths combined during hibernation and emergence thermal periods. Temperatures are separated by habitat types (forests, hibernacula, and clearcuts) and by slope aspects. Starred (*) values are significantly different (P < 0.05 and Δ°C > 1) from each other/others across habitat types for associated thermal period and slope aspect. Total mean values are reported for each habitat type at the bottom of the table. .....................................................................................................58 

vi

LIST OF FIGURES

Figure Page

Figure 1. Regional and local map of the study area in south-central Indiana. a) The location of the study area in Indiana relative to the continental US. b) The nine study sites spanning Morgan, Monroe, and Brown Counties in IN. Polygon colors represent management classes (clearcuts = medium grey, group selections = dark, controls = light) ..........................................................................................................26 

Figure 2. Scatter plot of daily distances traveled by Eastern Box Turtles (steplengths; y-axes) by ground temperature (Tg in °C; x-axes). All 2007-10 steplengths in meters per day by ground temperature (a.) and the log-transformed steplength by ground temperature (b.). Pre-harvest (2007-08) steplength in meters per day by ground temperature (c.) and post-harvest (2009-10; d.). Plots show 95% (black ellipse) and 50% (grey ellipse) density ellipses around points and histogram densities along plot boarders. Darkened areas represent the peak of activity temperatures (22-26°C; thermal optimum) in these data. ..........................................29 

Figure 3. Average steplength (m/day) moved by Eastern Box Turtles each month for both harvest periods (pre-harvest [2007-08] and post-harvest [2009-10]; bars). The average ground temperatures (Tg; °C) recorded at turtle location each harvest period are also plotted (lines). ....................................................................................30 

Figure 4. Mean monthly temperature maxima (Tmax), mean (Tmean), and minima (Tmin) over two years (2009-2010) by habitat type (clearcut openings, group selection openings, harvest-adjacent forest (Harv. Adjacent), and forested control) (a). Maxima, means, and minima monthly Eastern Box Turtle body temperatures (Tb) for the same period (b). ......................................................................................31 

Figure 5. Mean Eastern Box Turtle body temperatures (Tb) in degree Celsius (C) with relation to timber harvest proximity over the active season months for post-harvest years (2009-10 combined). Starred bars represent significantly different mean temperatures during that month. .................................................................................32 

vii

Figure Page

Figure 6. Study Site Map. Map of Indiana with study area in Morgan, Monroe, and Brown Counties outlined (inset) and the six study sites (3 clearcut treatment sites and 3 control sites) as part of the Hardwood Ecosystem Experiment in south-central Indiana. All radiotelemetered turtle hibernacula are indicated as dark dots. 59 

Figure 7. TPS Setup and Arrangement. Schematic of thermal profile stakes (TPS) with temperature loggers affixed at 10-cm increments (not to scale). The TPS recorded the microclimate through the hibernal season (hibernation and emergence periods). Temperatures collected from temperature loggers at each depth were matched to turtle temperatures (Tb) in order to inform the depth to which turtles hibernated and when they emerged (verified by radiotelemetry) (a). A subset of TPS and turtle hibernacula physical locations with relation to the management types (clearcut treatment and control) (b). ..........................................................................................60 

Figure 8. Hibernation Temperatures. Mean hibernacula temperatures recorded by week at various depths (+10, 0, -10, -20, &-30) and mean turtle body temperatures. Figure illustrates the point of inversion (between 23 February and 7 Mar 2010), demarcating the hibernation period (weeks 2 through 17) and emergence period (weeks 18 through 22). See text for details and further description. .........................61 

Figure 9. Habitat Temperatures by Depth. Mean location TPS temperatures (°C) by depth (centimeters) during the hibernation and emergence periods. Temperatures found at hibernacula and forests were not significantly different at varying depths. However, temperatures found in treatments were significantly colder (hibernation period) or warmer (emergence period) at nearly all depths. ......................................62 

viii

ABSTRACT

Currylow, Andrea F. M.S., Purdue University, May 2011. Effects of Forest Management on the Ecology and Behavior of Eastern Box Turtles. Major Professor: Rod N. Williams.

Declines in long-lived and geographically widespread forest animals, such as the case

with Eastern Box Turtles (Terrapene carolina carolina), warrants investigation. Despite

declines, this species’ ability to endure in a range of available habitat and its

physiological ties to environmental flux make it ideal for study of habitat use and

selection amid anthropogenic disturbances. For my thesis work, I focused on

investigating the ecology and behavior of Eastern Box Turtles following timber harvests.

As part of the Hardwood Ecosystem Experiment, I used nine experimental forest

management sites to investigate the effects of clearcut harvest openings and group

selection harvest openings on box turtles. I used standard homing radiotelemetry to

collect GPS location, morphometric, temperature, and behavior data on 50 adult Eastern

Box Turtles. I conducted the majority of this work during the active seasons (May –

October) but during the winter of 2010 I investigated the hibernal thermal ecology within

clearcut harvest openings. Combined with the radiotelemetry data previously collected

on these turtles from 2007-08, I was able to measure the effects of the harvests by

analyses of movement parameters and temperatures. I found that timber harvests had no

effect on the typical measurement of home range size, 100% Minimum Convex Polygons

(MCP), however the MCPs here are 33% larger than any other published report for this

species. Additionally, I found that turtles decreased the daily distances they traveled by

approximately 30%, but their thermal optima increased by 8% following the harvests.

Microclimates inside the timber harvests were significantly warmer (29%) in the summer

and colder (31%) in the winter than forested habitats, effectively excluding many animals

ix

from consistently using them. Instead of leaving the harvested areas, however, turtles

continued to use them differently. During the active season, box turtles used the edges of

harvest areas apparently for behavioral thermoregulation and possibly for foraging.

Turtles that used the harvest areas maintained 9% higher body temperatures during the

active season than those that did not. During the winter, turtles generally burrowed to 10

cm for overwintering, but depth varied by slope and gender. I found that the depth

influenced the emergence timing, which was also correlated with a soil-surface

temperature inversion. A single female turtle that hibernated in a group-selection harvest

opening had an estimated burrowing depth of nearly 30 cm to maintain her hibernal body

temperature. Moreover, I estimated the annual survival rate (96.2%) of box turtles in our

population, the first for the Midwest.

The investigation of ecological mechanisms underlying species declines has become

paramount in conservation literature. Simply reporting the extirpation of populations

without testing mechanistic causes does little to promote conservation management.

Herein, I investigated temporal thermal habitat availability, habitat use, thermal behavior,

survival, and intersexual differences among Eastern Box Turtles within the framework of

a managed forest setting.

1

CHAPTER 1: SHORT-TERM FOREST MANAGEMENT EFFECTS ON A LONG-

LIVED ECTOTHERM

Abstract

Timber harvesting has been shown to have both positive and negative effects on

forest dwelling species. I examined the immediate effects of timber harvests (clearcuts

and group selection openings) on ectotherm behavior, using the Eastern Box Turtle as a

model. I monitored the movement and thermal ecology of 50 adult box turtles using

radiotelemetry from May-October for two years prior to, and two years following

scheduled timber harvests in the Central Hardwoods Region of the U.S. Box turtle

annual home ranges (7.45 ha, 100% MCP) did not differ in any year or in response to

timber harvests, but were 33% larger than previous estimates (range 0.47-187.67 ha).

Distance of daily movements decreased post-harvest (from 22 m ± 1.2 m to 15 m ± 0.9

m) whereas thermal optima increased (from 23 ± 1°C to 25 ± 1°C). Microclimatic

conditions varied by habitat type, but monthly average temperatures were warmer in

harvested areas by as much as 13°C. Turtles that used harvest openings were exposed to

extreme monthly average temperatures (~40°C). As a result, turtles made shorter and

more frequent movements in and out of the harvest areas while maintaining 9% higher

body temperatures.. This experimental design coupled with radiotelemetry and

behavioral observation of a wild ectothermic population prior to and in response to

anthropogenic habitat alteration is the first of its kind. Our results indicate that in a

relatively contiguous forested landscape, small-scale timber harvests have modest effects

on the short-term behavior of box turtles. Ultimately, the results of this research can

benefit the conservation and management of temperature-dependent species by informing

effects of timber management across landscapes.

2

Introduction

Study of habitat alteration through direct and indirect anthropogenic episodes such as

reduction of forest habitats and changing climate is becoming increasingly frequent. The

understanding of how these changes affect the physiology and behavior of native fauna is

vital to the preservation of diversity. Timber harvesting is likely one of the most

prominent land uses affecting forest wildlife (Peterman & Semlitsch 2009). Forest

management practices change the vegetative structure and local temperature, which may

affect community structure and function (Renken et al. 2004). Environmental flux also

has a greater effect on movements and behavior of poikilotherms than for homeothermic

species (Allard 1935; Bayless 1984). In response, timber harvests have been implicated

as a possible cause for worldwide herpetofaunal declines (Gibbons et al. 2000; Pechmann

et al. 1991; Wake 1991). As a result, management of our eastern hardwood forests has

become a balancing act between timber production and ecological conservation.

While some data suggest that heavily logged areas are associated with moderate

increases in bird and reptile diversity (Fredericksen et al. 2000), it is not clear whether

this can be considered a general trend for all taxa. Timber harvesting has the potential to

affect multiple facets of how ectotherms utilize available habitat both directly and

indirectly. Canopy openings may create basking sites or allow herbaceous mass to

flourish and provide basilar food sources (Perison et al. 1997). Edge effects of openings

and access roads have been shown to influence habitat resources into the forest interior at

varying distances (Cadenasso & Pickett 2001; Delgado García et al. 2007; Donovan et al.

1997). Because variation in resources such as vegetation and invertebrate prey occur,

daily movements and annual home range sizes may readily expand, contract, or shift in

response to this variation. Moreover, the behavior, physiology, and even fitness of

ectotherms are strongly affected by temperature fluctuations (Cunnington et al. 2009;

Huey & Kingsolver 1989). Temperature dictates ectothermic habitat use based on the

animals thermal optima (i.e., the temperature at which movement activity is maximal;

Huey & Kingsolver 1989) which in turn alters behavior (Bradshaw & Holzapfel 2007;

Fox et al. 2003).

3

Recent attempts to assess the effects of timber harvests on many ectothermic species

often suffer from the lack of replication or comparable pre-harvest data (e.g. Goldstein et

al. 2005; McLeod & Gates 1998). Furthermore, the majority of these herpetofaunal

studies have focused on the harvest effects on amphibian populations (e.g. Hocking &

Semlitsch 2008; Peterman & Semlitsch 2009; Rittenhouse & Semlitsch 2009;

Rittenhouse et al. 2009; Semlitsch et al. 2009), while relatively little is known about the

impacts on reptile populations. However, the existing data suggest reptiles are not only

sensitive to habitat perturbations, but that the impacts are more pervasive and severe than

for amphibians (Gibbons et al. 2000). Negative impacts to reproductive adult reptiles,

such as long-lived, K-selected turtles, can devastate entire populations (Brooks et al.

1991; Gibbs & Shriver 2002). Box turtles, which are among the longest lived of all

reptiles, are geographically widespread throughout the eastern forests, yet they are

sensitive to environmental disturbances that affect local habitat features (Currylow et al.

2011; Dodd 2001; MacGowan et al. 2004). Widespread population declines have

sparked interest in the conservation of this species. While basic data exist on the habitat

requirements of box turtles, many studies were conducted at a single location and did not

empirically assess responses to changing habitat or microenvironmental conditions.

The investigation of ecological mechanisms underlying species declines has become

paramount in conservation literature. Simply reporting the extirpation of populations

without testing mechanistic causes does little to promote conservation management.

Herein, I investigated temporal thermal habitat availability, habitat use, thermal behavior,

and intersexual differences among Eastern Box Turtles (Terrapene carolina carolina)

within the framework of a managed forest setting. The overarching goals of this study

were to examine ectothermic response to timber harvesting at both the landscape and

local scales. At the landscape scale, our specific goals were to assess effects of various

timber harvest regimes on habitat use, thermal environments, and turtle thermal ecology.

At the local level, our specific goals were to investigate edge effects of timber harvests on

box turtle thermoregulatory behavior, movement metrics (frequency of movement and

steplength), and observed behavior.

4

Methods

Study Area

The research was conducted within approximately 35,000 hectares of Morgan-

Monroe State Forest (MMSF) and Yellowwood State Forest (YSF) in Morgan, Monroe,

and Brown Counties, Indiana (Figure 1a). From the years 1860 through 1910, the

forestland was characterized by routine burning and cutting for cattle grazing. At the turn

of the 20th century, the state of Indiana began purchasing the land and establishing these

State Forests. Now, MMSF and YSF boundaries are shared, forming a relatively

contiguous forested habitat characterized by hills and ravines of hardwood, deciduous

forests with scattered gravel access roads. This is an oak-hickory dominated forest, with

the majority of canopy species being Quercus spp., such as Q. montnana (chestnut oak),

and Carya cordiformis and C. ovata (butternut and shagbark hickory; Summerville et al.

2009). These State Forests are managed for multiple-uses including recreation,

education, research, and timber harvesting.

Forest Management Design and Sampling

Our research is part a long-term (100-yr), landscape-scale (spanning 31 linear

kilometers and 3,601 hectares) timber and wildlife research collaborative designed for the

study of ecological and social impacts of various silvicultural methods typically

employed in the Midwest (Hardwood Ecosystem Experiment). In 2007, I identified nine

study sites of approximately 400-ha, each assigned to one of three forest management

classes in a randomized complete block design (Figure 1b). The management classes

included two 2.72 – 4.43-ha clearcuts, eight 0.15 – 2.55-ha group selection openings, and

forested controls. The timber harvests were implemented on equal numbers of

southwest- and northeast-facing slopes over the winter of 2008-09 within the center 90-ha

of each study site. The remaining 300+ hectares at each site remained intact to serve as

refugia and maintain species diversity.

To determine the effects of timber harvests on T. c. carolina, I collected GPS location

and habitat use data before timber harvests (pre-harvest; 2007-08) and after harvests

5

(post-harvest; 2009-10). I initially located adult box turtles by meandering-transect

visual encounter surveys. Upon capture, I assigned a unique ID number and marked each

turtle using a triangle file along the marginal scutes following a modified Cagle scheme

(Cagle 1939; Ernst et al. 1974; Ferner 2007), recorded morphometrics, and affixed a

transmitter (model RI-2B Holohil Systems, Ltd., Ontario, Canada) to the carapace.

Where possible, sex ratios and numbers of turtles were equally divided among sites and

management classes. I subsequently radio-tracked (homing) turtles 2-3 times per week

during the active seasons (May through October). For each tracked location, I recorded

GPS coordinates, date, ground temperature, elevation, and during the post-harvest years I

also recorded observed activity classifications (resting, eating, mating, basking, walking,

etc.).

To monitor the thermoregulatory behavior of turtles post-harvest, I affixed iButton

temperature dataloggers (model DS1921G-F5#, Maxim Integrated Products, Inc.,

Sunnyvale, CA) to the carapace of each of the tracked turtles in May 2009. Since

carapacial temperature measurements have been shown to correlate well with deep body

temperatures (Bernstein & Black 2005; Congdon et al. 1989; do Amaral et al. 2002;

Peterson 1987), I used the dataloggers to represent each turtle’s body temperature (Tb).

Temperature datalogger and transmitter weight combined was usually no more than 5%

(max 20 g) of the animal’s total body weight. Dataloggers recorded temperatures every

45 minutes during the active season (May-October).

To assess the available thermal habitats in harvest areas versus uncut forests, I

measured ambient temperature using temperature dataloggers affixed to stakes, 10 cm

from soil surface (at approximately T. c. carolina carapace height). I randomly placed

these ‘environmental dataloggers’ at four sample locations within each of the nine study

sites for a total of 36 individual thermal locations. In each clearcut management site, two

environmental dataloggers were randomly deployed inside clearcuts and two in the

adjacent forests (between 100 m and 500 m from the nearest harvest edge; harvest-

adjacent forest). In each group selection management site, four dataloggers were

randomly deployed inside harvest openings. In each control site, four dataloggers were

6

randomly deployed in forested habitats. This blocked design resulted in equal numbers

of environmental dataloggers inside harvest openings (n=18) and in forested areas (n=18)

representing the four habitat types (clearcut opening, group selection opening, harvest-

adjacent forest, and forested control). To eliminate the effect of slope aspect on

temperature logged, I used equal numbers of southwest- and northeast -facing slopes. I

deployed all temperature loggers from May 2009 to October 2010 for a total of 75 weeks.

I programmed dataloggers to record temperatures every 45 minutes to match the

carapacial dataloggers described above.

Landscape-Scale Analyses

Home range estimation

I used multiple analyses to examine how various timber-harvesting regimes affect

behavior at landscape- and local-scales. To describe landscape-scale effects of timber

harvests on box turtles, I used all turtle location data across all nine study sites throughout

the forested landscape. To characterize spatial land use in our population of box turtles, I

created a point layer in ArcGIS 9 (version 9.3.1; ESRI 2009) using the GPS location data

and calculated 100% Minimum Convex Polygons (MCP) with the Hawth’s Analysis

Tools extension (Beyer 2004) for each turtle in each year, thus creating annual MCP

home ranges. I standardized all annual MCP home ranges by the number of GPS

locations and log-transformed them for normality.

I used a generalized linear mixed model to test annual MCP home ranges for

differences among sites using a crossover design and the PROC GLMMIX command in

SAS (SAS Institute Inc. 2007) with a first-order autoregressive covariance structure. I

compared all the pre-harvest data then “crossed over” to the post-harvest control

comparisons. In my initial model, site, year, and the interaction of site and year were

fixed effects and turtle ID nested in site was a random effect. By analyzing data in this

cross-over fashion, I could verify that control sites were representative of pre-harvest

conditions (i.e., site explained very little variation). I grouped sites by management class

(clearcut, group selection, and control) for all subsequent analyses and evaluated their

7

effects in the pre- and post-harvest data using a full factorial generalized linear mixed

model (GLMM) with unbounded variance components in JMP (SAS Institute Inc. 2008).

I used year, sex, management class, and their interactions as fixed effects and turtle ID

nested in year as a random effect (to account for repeated measures of individual turtles)

to find any differences in annual MCP home ranges with relation to harvests. To detect

significant differences across effect levels, I used post-hoc Least Squares Means

(LSMeans) Tukey-Kramer pairwise comparisons, which adjusts significance for multiple

comparisons.

Year-to-year variation in movements and habitat use is common (often due to

variation in resources such as vegetation and invertebrate prey; Dodd 2001; Schwartz et

al. 1984; Stickel 1989), therefore I used biennial (two-year) intervals as indices of longer-

term home range sizes and core use areas. These biennial intervals corresponded to the

two pre-harvest years and two post-harvest years (hereafter “harvest periods”). To assess

differential habitat utilization due to timber harvests, I used biennial MCPs and kernel

estimates (ArcGIS Home Range Tools [HRT] extension; Rodgers et al. 2005) for each

turtle between harvest periods. I chose to use kernel estimates for further comparisons to

other habitat use studies (Worton 1989) but also continued to calculate MCPs because it

has been argued they they better represent herpetofaunal habitat use (Row & Blouin-

Demers 2006). I calculated 50-, 90-, and 95-percent kernel isopleths (percent volume

contour) of utilization distributions using the fixed kernel method with least squares cross

validation (LSCV) for pre- and post-harvest. For both biennial MCP and kernels, I used

a GLMM to test for differences in pre- and post-harvest area measurements (log-

transformed) caused by the fixed effect of harvest period (with turtle ID nested as a

random effect to control for re-sampling error).

Movement and thermal ecology

Turtles may not only adjust their annual home ranges in response to harvests, but vary

their movement activity (i.e. move farther distances within their home range or move

more frequently). For this analysis, I calculated the Euclidian distance between GPS

locations for each turtle in ArcGIS using the HRT extension then calculated steplength

8

(average estimated distances by day). To test whether harvest period had an effect on

steplength, I log-transformed these data and fitted a full factorial unbounded GLMM with

harvest period, sex, management class, and their interactions as fixed effects and turtle ID

nested in harvest period as a random effect. Then to examine the thermal ecology of T. c.

carolina in relation to the timber harvests, I tested for correlation between the log-

transformed steplength data and ground temperature (Tg; recorded when turtles were

radio-located). I also used these data to find the thermal optima (the temperature at

which movement activity is maximal) across harvest periods.

Thermal habitats

To test for changes in available thermal habitat, I used differences in ambient

temperature among habitat types within sites. I summarized the temperature time series

data from each of the 36 environmental dataloggers into three variables - monthly

temperature maxima (Tmax), monthly temperature minima (Tmin), and monthly

temperature mean (Tmean) using R (R Development Core Team 2009). I used unbounded

GLMM in JMP to test for significant Tmin, Tmax, and Tmean differences caused by habitat

type, month, and their interaction as fixed effects and individual datalogger ID nested in

month as the random effect. I used LSMeans Tukey-Kramer post-hoc comparisons to

detect significant differences in Tmin, Tmax, and Tmean between months.

Local-Scale Analyses

To determine the thermal effects of harvests on box turtle behavior, I first

characterized the thermoregulatory behavior of our entire population. I examined the

max, mean, and min Tb to find the range of selected temperatures for each month. I

correlated observed behavior at the time of each GPS location in relation to Tb. I used a

GLMM to investigate turtle body temperature (Tb) differences explained by the fixed

effect of observed behavior category with the random effect of turtle ID nested in

behavior. Behavior categories included basking, eating, mating, resting, inverted (found

upside-down), walking, and buried.

9

To investigate local-scale harvest edge use and activity, I examined the actual harvest

openings and their associated edges in combination with GPS location data. I then

created 10- and 50-meter polygon buffers around the harvest boundaries using ArcGIS

Analysis Tools. I tested for differences in the percent of turtle locations within these

three harvest-polygons (inside harvest, 10 m buffer, and within the 50 m buffer) across

harvest periods, again controlling for individual effects using an unbounded GLMM as

described above. I conducted a similar analysis using the Euclidian distances turtles

moved within these harvest-polygons to test for differences in activity (frequency of

movement or daily distance moved).

To determine the edge effects for thermoregulation, I compared Tb of turtles using the

harvests and their edges to the Tb of those same turtles when they were located in the

forests. To investigate edge effects on turtle movement activity, I used Tb to describe the

available thermal habitats in various harvest-polygons. I analyzed harvest edge effects by

categorizing harvest proximity polygons (as above) by inside the harvest, 10 m buffer,

and 50 m buffer from the nearest harvest opening. I also explored Tb within harvest-

polygons by using Tb as the response variable and distance to harvest and month as the

fixed effects. I used unbounded GLMMs and controlled for repeated measures using

turtle ID nested in harvest-polygons as a random effect in each model. Post-hoc

LSMeans Tukey-Kramer pairwise comparisons was performed to detect significant

differences.

Results

Landscape-Scale Effects

I radio-tracked 23-44 T. c. carolina each year (average = 33.5/year), carrying over all

that survived each year and were not lost or censored. Losses due to transmitter failure

were rare (n = 1). Two turtles were separated from their transmitters and censored. Five

turtles died of various causes including predation (n = 1), severe emaciation (n = 1),

suspected disease (n = 2), or failure to emerge from hibernacula (n = 1). Home range

MCPs for the remaining turtles (n = 50; 23♂, 27♀) with > 20 locations per year (avg. =

10

57.34, SD = 19.10, range = 14-79) were calculated for each year and are summarized in

Appendix 1.

I found no difference (P-value = 0.418) in the overall size of T. c. carolina annual

MCP home ranges between all pre-harvest sites and control post-harvest sites, verifying

our experiment used true controls. Annual MCP home ranges (4.10 ha to 11.43 ha) did

not differ among sex, year (2007-10), management class, or any combination of these

factors (all P-values > 0.07). The annual minimum and maximum home range sizes were

0.47 ha and 187.67 ha, respectively. The average MCP for all four years was 9.14 ha for

males and 5.55 ha for females.

Pre-harvest biennial MCP home ranges (18.93 ha, SE = 7.51) were generally larger

than post-harvest (9.09 ha SE = 5.75; Table 1), however, this difference was not

significant (F1, 2.435 = 0.018, P = 0.90). There was much variation in kernel areas by sex

and harvest period (Table 1) For all three kernel isopleths (50-, 90-, and 95%), the home

range areas increased from pre-harvest to post-harvest (all P-values < 0.05). No variation

in biennial home range area was attributed to harvest type (clearcut or group selection) or

sex (all P-values > 0.29).

Movements and thermal ecology

Steplength decreased from pre-harvest to post-harvest (F1, 66.2 = 33.96, P < 0.001) but

there were no differences (all P-values > 0.13) by sex, management class, or any

combination of the three. The percent of steplengths that equaled zero (the percent of

time the turtles did not change position between GPS locations) was 1.83% pre-harvest

and 0.86% post-harvest, meaning the turtles moved more often post-harvest. Steplength

was positively and significantly correlated with ground temperature (R2 = 0.16, P <

0.001; Figure 2a & b). Thermal optimum was found at 22-24°C pre-harvest (Figure 2c)

and 24-26°C post-harvest (Figure 2d). Average steplength during the pre-harvest period

was 22.08 meters (SE = 1.21) and 15.40 meters (SE = 0.88) during the post-harvest

period, with the height of activity varying by month (Figure 3). The thermal optima were

22-24°C during the pre-harvest period and between 24-26°C post-harvest despite the fact

11

that ground temperatures were higher pre-harvest (mean = 24.5°C) than post-harvest

(mean = 22.7°C; F1, 7315 = 140.8, P < 0.001).

Thermal habitats

I processed 388,974 environmental temperatures from 36 locations in four habitat

types (clearcut opening, group selection opening, harvest-adjacent forest, and forested

control) between May 2009 and October 2010. Available temperatures differed at each

level (Tmax, Tmean, and Tmin) for each habitat type, month, and habitat by month

interaction. The interaction term for Tmin was the only non-significant effect (F33, 376.6 =

0.959, P = 0.54) in the model. The strength of the effects varied by month, with the

harvest habitat types (clearcut and group selection openings) more similar to one another

and forested habitat types (harvest-adjacent forest and forested controls) more similar

(Table 2). Habitat type affected Tmax more strongly than others. Explicitly, the range of

temperatures for Tmax was broader between habitats than for Tmin or Tmean especially

during the active period (Figure 4a). Between March and October, Tmax in both harvest

habitat types were significantly warmer (>10°C) than forested habitats (forests Tmax =

24.57°C, SE = 0.73; harvest Tmax = 34.43°C, SE = 0.80; F1, 40.25 = 83.56, P < 0.001). This

difference was most extreme in August when the Tmax in harvest areas averaged 39.98°C

(SE = 0.99) while it was nearly 13°C cooler in forested areas at 27.49°C (SE = 0.88). In

contrast, Tmin and Tmean differences remained within 3°C between habitat types, but

usually less than 2°C for these months.

Local-Scale Effects

I recorded and processed 494,548 body temperatures among 50 turtles between May

2009 and October 2010. The maximum, mean, and minimum Tb varied by month (Figure

4b). Tb was highly correlated with Tg (R2 = 0.71, P < 0.001). Behavioral categories were

correlated with Tb over the post-harvest period, but explained very little of the variation

(R2 = 0.08, P < 0.001). Post-hoc analysis revealed significant Tb differences in basking,

walking, resting, and being underground behaviors. Behaviors associated with higher Tb

(24-27°C) included basking and mating. Behaviors generally associated with lower Tb

(22-23C°) included resting, inverted, walking, and eating, but post-hoc analysis revealed

12

that these were not significantly different than mating. When Tb decreased to an average

of 13.8°C, the turtles were generally buried underground (near the hibernation season).

I found no significant difference in number of turtle locations between the harvest

periods within harvest-polygons. While the pre-harvest Euclidian distances within the

designated harvest boundaries and their edges did not differ from 2007 to 2008, the

averages were significantly different from post-harvest Euclidian distances in each

polygon (F1, 516.5 = 32.45, P < 0.001). Inside the harvest boundaries, post-harvest

Euclidian distances were shorter (11.26 m, SE = 1.66) compared to pre-harvest Euclidian

distances of 22.91 m (SE = 2.83). A similar trend was found within edge polygons where

post-harvest Euclidian distances (14.45 m, SE = 1.27) were smaller than pre-harvest

(23.60 m, SE = 2.10).

Body temperatures did not vary among management classes (F2, 40.72 = 1.624, P =

0.21) but were different among months (F6, 294.7 = 1087.334, P < 0.001; Figure 5).

However, turtles found within the harvest openings maintained 9% higher Tb overall than

those found in the forest/harvest edge or forest interior (F2, 73.24 = 8.135, P < 0.001).

Body temperatures within 50 meters of the harvest edges were lower (21.72°C, SE =

0.35) than farther inside the forest (22.22°C, SE = 0.21) and harvests (23.91°C, SE =

0.44).

Discussion

Recent literature has shown that timber harvesting can have both positive and

negative effects on forest dwelling species. Here I investigated the effect of various

harvest openings on an ectotherm, the Eastern Box Turtle. Using an experimental design

and a variety of approaches, I demonstrate that in a relatively contiguous forested

landscape, timber harvests have little effect on the short-term annual behavior of box

turtles. However, I did detect a behavioral effect at the local scale where available

microenvironmental temperatures are altered. I also offer further evidence that there is

much variation in the annual behavior and home ranges of T. c. carolina that should be

considered when establishing management strategies for forests and this species.

13

Landscape-Scale Effects – home ranges and thermal ecology

Box turtles will preferentially use certain types of available habitats for

thermoregulation, nesting, and aestivation (Madden 1975; Schwartz & Schwartz 1974).

Home range size of this species likely depends on the quality of available food and other

resources within the habitat (Dodd 2001). Annual MCP home ranges for our adult T. c.

carolina ranged from 0.47 and 187.67 hectares, the upper extreme being much larger than

reports from any other study on this species. Indeed, our average annual home range

estimate of 7.45 ha is more than 33% larger than any other published estimates to date

(Table 3; Bayless 1984; Dolbeer 1969; Donaldson & Echternacht 2005; Hallgren-Scaffidi

1986; Nichols 1939; Quinn 2008; Stickel 1989; Strang 1983; Williams & Parker 1987).

It should be noted that there is a large variance in home range estimates across studies,

which is likely associated with study duration, size, and monitoring method. The most

likely explanation for the large home range size reported here is that my study was

conducted within an expansive, relatively contiguous, and undisturbed habitat. Iglay et

al. (2007) found that turtles in fragmented habitats moved less often than those in

contiguous habitats. To this end, many previous studies were conducted within relatively

small and fragmented habitats that likely physically limited home ranges (Table 3).

In this study, I found no differences in either annual or biennial home ranges across

the landscape in association with any of the three management classes (clearcut opening,

group selection opening, or control). This lack of variation was likely due to the fact that

the actual timber harvest openings were relatively small (0.15 – 4.43 ha) in relation to T.

c. carolina home range size and the surrounding contiguous forested habitat. Forest

species often develop different strategies to cope with habitat perturbations. Some

species expand their home ranges in response to forest fragmentation (Hansbauer et al.

2008) while others inhabit territories that contain only small percentages of preferred

habitat or(Andrén 1994). Still other species may gravitate toward mixed-composition

habitat (Andrén 1992). In the current study, the percent of turtle locations within harvest

edges did not change from pre- to post-harvest; suggesting that no such gravitation

occurred. However, the movement parameters I investigated suggested that turtles did

alter their behavior while in proximity to harvest boundaries.

14

In pre-harvest years, turtles tended to move longer distances (i.e., longer steplengths)

than post-harvest years. However, the percent of steplengths that were zero were higher

pre-harvest (1.83% vs. 0.86%). This suggests that although turtles moved shorter

distances and maintained generally smaller home ranges after the harvests were

implemented, they moved more often. These increased short-range movements may be

the result of changes in resources. Turtles in this altered habitat may need to move

frequently for new foraging opportunities as seen with many small mammal and bird

species (Debinski & Holt 2000; Hansbauer et al. 2008). Shorter movements may be a

result of downed slash acting as physical barriers or severe climatic conditions (i.e.,

drought). While it was evident that turtles did reduce movements during drought years,

the cumulative effect on our results is minimal because turtles experienced drought years

during pre-harvest 2007 and post-harvest 2010. Alternatively, behavioral

thermoregulation may explain why turtles regularly moved but remained nearer to the

same locations post-harvest.

Studies of fine-scale temperatures over broad spatial expanses are rare, despite the

fact that temperature is an important factor in the location and activity of species

(Cunnington et al. 2009). A primary effect of the alteration of landscapes is the change in

the microclimate of available habitats (Saunders et al. 1991). I measured these changes

temporally across the landscape using temperature dataloggers. Although there was

annual variation in ambient temperatures, the microclimatic conditions varied

significantly between harvest and forested habitats. The most pronounced period

occurred between May and September for Tmax when differences were often greater than

10°C. These extreme summer temperatures found within harvest areas potentially

exclude many plant and animal species. For example, variation in microclimates has

been shown to affect the germination of emergent herbaceous and woody species

(Breshears et al. 1998). During periods of highest temperatures, Tmax within harvest areas

was often observed to be near the maximum thermal tolerance for most ectotherms

(43°C) effectively reducing the suitability of these areas for T. carolina (34.2°C; Penick

et al. 2002) and other herpetofauna (Blem et al. 1986; Brattstrom 1965; Hutchison et al.

1966; Kroll 1973). Although the current study examines a subset of factors affected by

15

timber harvests, the advantage of this approach is the resulting detailed data of

mechanisms underlying landscape effects (Debinski & Holt 2000). My results suggest

that population-level responses to small-scale timber harvests (which are typical for the

Midwestern U.S.) are minimal.

Local-Scale Effects – movement and edge effects

Ecotones (either natural or man-made) will influence box turtle activity differently

as surface temperature, air temperature, and canopy cover varies across the landscape

(Strang 1983; Weiss 2009). Ecotones at the harvest edges may provide cover by fallen

logs and downed treetops, increased concentration and variety of forage (soft mast plants

and invertebrates), and may facilitate behavioral thermoregulation by providing basking

sites. Although I found no significant difference in the relative number of turtle locations

within the boundary or edges of the harvest areas, I did find differences in the movement

metrics that suggest the turtles use these areas differently. Prior to the harvests, turtles

made longer, scattered movements across would-be harvest areas. Once the harvests

were implemented, the movements across the harvests shortened and were concentrated

along the edges of the harvests. Directed movements, although varied, often would

alternate from the forest to the harvest edge, and frequently would cross logging roads to

do so. Studies on various turtle species have determined that roads bisecting turtle routes

were positively correlated with male biased sex ratios (Gibbs & Shriver 2002; Kipp 2003;

Marchand & Litvaitis 2004; Gibbs & Steen 2005; Steen et al. 2006), population declines

(Shepard et al. 2008), and expanded home range sizes (Nieuwolt 1996). In this study,

two of the sites were bordered by public roads and all sites were adjacent to logging

roads, however, there appeared to be no associations between roads and home ranges.

Anthropogenic effects extend beyond the physical boundary of disturbance. In a

broader definition of habitat, thermal microclimates limit the use of certain areas both

seasonally and spatially. Analyses of the variables that affect ambient temperatures on a

microclimate scale will aide in the understanding of habitat requirements of ectotherms

(Cunnington et al. 2009). In this study, turtles found inside the harvest areas maintained

higher active season body temperatures than those outside the harvests by 10.13%. As

16

expected, basking behavior correlated with higher temperatures. Forested sites located

near roads or open areas such as timber harvests, are found to be generally warmer than

those further away (Cunnington et al. 2009). However, Tb at timber harvest edges were

the lowest during the active period, even lower than in the adjacent forested habitat

suggesting that box turtles were moving between microhabitats for thermoregulation as

seen in other taxa (Adolph 1990; Sepulveda et al. 2008). Turtles within our experimental

openings were exposed to a wide range of temperatures. In a laboratory study, the

specificity of Tb was investigated between T. c. carolina and T. ornata with the finding

that T. c. carolina has less thermal specificity (do Amaral et al. 2002). I routinely found

turtles walking while inside the harvests and document that they do have the ability to

behaviorally adjust to varying temperatures at a fine scale. These adjustments may play

key roles in the physiological requirements of ectotherms throughout ontogeny and in

various physical conditions (e.g., in reptiles, gravid females actively adjust to maintain

higher body temperatures than males; Tozetti et al. 2010).

Open spaces, such as clearcuts, may have less of an effect on larger-bodied species or

those adapted to hot and dry conditions. Canopy cover directly influences light intensity,

which is known to be a critical factor for many reptiles during activity periods (Gould

1957; Rose & Judd 1975; Todd & Andrews 2008). On the other hand, many reptilian

species such as small-bodied snakes are adapted to utilize leaf litter and are likely to be

adversely affected by its removal with associated timber harvests (Todd & Andrews

2008). During the active season, T. c. carolina use leaf litter to create ‘forms’ as cover

(Stickel 1950). T. c. carolina will use these forms throughout the active period as refuge

from the heat, cold, rain, or disturbance (Dodd 2001). In addition to cover, leaf litter

serves as habitat for prey (such as snails, worms, and mushrooms) of box turtles.

Immediately following implementation of harvests, leaf litter is degraded, blown from

these areas, and often leaves large patches of unsuitable bare ground (Enge & Marion

1986). Studies have found that the increased soil temperatures and reduced leaf-litter

cover (which can take decades to return pre-harvest conditions) in previously cut areas

exclude many amphibian species (Crawford & Semlitsch 2008; Petranka et al. 1993). I

found that short term effects such as the loss of leaf litter did not cause box turtles to

17

abandon the area, but rather continue to use it in a different way (such as for

thermoregulation).

Conservation Implications

Merely reporting species declines without determining their mechanistic causes

leaves conservation planners with little recourse. To date, no studies have monitored the

response of an ectotherm’s movement parameters prior to and after discrete

anthropogenic disturbance such as timber harvests. The present study has yielded detailed

data on box turtle habitat use and spatial ecology in a managed forest, but has much

broader implications on multiple forest-dwelling species. In my study, the timber harvest

openings were fairly small (< 5 ha) and were contained in a relatively contiguous and

much larger forest matrix. My results indicate that in a relatively contiguous forested

landscape, small-scale timber harvests have minimal effects on the short-term behavior of

box turtles. However, temperature fluctuations as seen in the current study may affect

seasonal available habitat for other forest-dwelling animals, especially for those with

limited dispersal and thermoregulatory capabilities. Altered microclimates can exclude

animals from harvest areas but also may create desired ecotonal habitats. Considerations

of habitat requirements and contiguity of surrounding refugia habitat and species ability

to recover should be thoroughly considered before timber harvest sizes are determined.

These factors are of particular interest when dealing with long-lived species of

conservation concern.

Acknowledgements

This paper is a contribution of the Hardwood Ecosystem Experiment, a partnership of

the Indiana Department of Natural Resources (IDNR), Purdue University, Ball State

University, Indiana State University, Drake University, and the Nature Conservancy.

Funding for the project was provided by the Indiana Division of Forestry Grant #E-9-6-

A558 and IDNR Division of Fish and Wildlife, Wildlife Diversity Section, State Wildlife

Improvement Grant #E2-08-WDS15. I thank field technicians A. Garcia, A. Hoffman, A.

Krainyk, B. Geboy, B. Johnson, B. Tomson, G. Stephens, H. Powell, J. Faller, J.

MacNeil, K. Creely, K. Lilly, K. Norris, K. Powers, K. Westerman, L. Keener-Eck, L.

18

Woody, M. Baragona, M. Cook, M. Cross, M. Turnquist, M. Wildnauer, N. Burgmeier,

N. Engbrecht, S. Johnson, S. Kimble, S. Ritchie, T. Jedele, and Z. Walker. I also thank

members of the Williams lab group for providing helpful comments on previous versions

of this manuscript. Research activities associated with this project fall under the Purdue

Animal Care and Use Protocols and amendments, PACUC 07-037 and IDNR Scientific

Purposes Licenses 09-0080 & 10-0083.

19

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25

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26

Figure 1. Regional and local map of the study area in south-central Indiana. a) The

location of the study area in Indiana relative to the continental US. b) The nine study

sites spanning Morgan, Monroe, and Brown Counties in IN. Polygon colors represent

management classes (clearcuts = medium grey, group selections = dark, controls = light)

27

Table 1. Pre-harvest (Pre-harv.; 2007-2008) and post-harvest (Post-harv.; 2009-2010)

home ranges of female and male Eastern Box Turtles. The associated management class

(Mngmnt Class) is listed and home ranges were calculated by biennial Minimum Convex

Polygons (MCP) and 95% kernel isopleths. Only the 95% kernel isopleths areas are

listed here, as they are the only relevant comparisons to 100% MCP.

Harvest

Period Sex Mngmnt Class n Biennial MCP Biennial 95% Kernel

Median Mean SE Median Mean SE

Pre-harv. F Clearcut 5 6.80 15.42 10.20 3.57 32.32 28.97

Control 4 3.52 4.54 1.86 3.32 3.37 0.73

GroupSelect 2 10.21 10.21 6.74 4.31 4.31 0.38

M Clearcut 5 2.02 4.63 1.75 2.71 4.34 1.07

Control 4 5.52 83.08 78.41 5.39 14.99 10.63

GroupSelect 7 3.53 5.70 2.81 3.85 4.35 1.11

Summary F All 11 5.27 10.52 4.74 3.94 16.70 13.15

M All 16 3.57 24.71 19.62 4.12 7.01 2.72

Totals 27 3.61 18.93 11.70 3.94 10.96 5.52

Post-harv. F Clearcut 7 2.57 10.56 5.80 1.45 1.85 0.51

Control 8 7.96 9.87 2.81 2.28 5.02 2.91

GroupSelect 9 2.69 5.48 1.89 1.30 1.36 0.23

M Clearcut 7 5.98 11.11 6.30 2.22 49.22 46.96

Control 7 3.65 16.72 13.10 1.59 18.66 17.29

GroupSelect 8 2.32 2.64 0.51 1.66 1.64 0.21

Summary F All 24 4.19 8.42 2.02 1.49 2.72 1.00

M All 22 3.02 9.82 4.57 1.75 22.19 15.69

Totals 46 3.02 9.09 2.40 1.57 12.03 7.57

28

Table 2. Least Squares Means (LS Mean) Tukey-Kramer post-hoc pairwise

comparisons connecting letters report of monthly environmental temperatures (Tmin,

Tmax, Tmean) during 2009-2010 within four habitat types (clearcut openings, group

selection openings, harvest-adjacent forest, and forested control). Habitat types at each

level not connected by the same letter are significantly different.

Level Habitat Type LS Mean

Tmean GroupSelection A 12.4068993

Clearcut A 12.3435027

Control B 11.4761091

Harv.Adjacent B 11.1620106

Tmax GroupSelection A 25.3953822

Clearcut A 24.6201529

Control B 17.7994578

Harv.Adjacent B 17.2141375

Tmin Control A 7.302016

Harv.Adjacent A 7.05775033

Clearcut B 5.99306883

GroupSelection B 5.84889568

29

Figure 2. Scatter plot of daily distances traveled by Eastern Box Turtles (steplengths;

y-axes) by ground temperature (Tg in °C; x-axes). All 2007-10 steplengths in meters per

day by ground temperature (a.) and the log-transformed steplength by ground temperature

(b.). Pre-harvest (2007-08) steplength in meters per day by ground temperature (c.) and

post-harvest (2009-10; d.). Plots show 95% (black ellipse) and 50% (grey ellipse)

density ellipses around points and histogram densities along plot boarders. Darkened

areas represent the peak of activity temperatures (22-26°C; thermal optimum) in these

data.

a.

c.

b.

d.

30

Figure 3. Average steplength (m/day) moved by Eastern Box Turtles each month for

both harvest periods (pre-harvest [2007-08] and post-harvest [2009-10]; bars). The

average ground temperatures (Tg; °C) recorded at turtle location each harvest period are

also plotted (lines).

0

5

10

15

20

25

30

35

40 PreTx

PostTx

TempPreTx

TempPostTx

Pre-harvest

Post-harvest

Tg Pre-harvest

Tg Post-harvest

31

Figure 4. Mean monthly temperature maxima (Tmax), mean (Tmean), and minima

(Tmin) over two years (2009-2010) by habitat type (clearcut openings, group selection

openings, harvest-adjacent forest (Harv. Adjacent), and forested control) (a). Maxima,

means, and minima monthly Eastern Box Turtle body temperatures (Tb) for the same

period (b).

32

0

5

10

15

20

25

April May June July August September October

Figure 5. Mean Eastern Box Turtle body temperatures (Tb) in degree Celsius

(C) with relation to timber harvest proximity over the active season months for post-

harvest years (2009-10 combined). Starred bars represent significantly different

mean temperatures during that month.

33

Tabl

e 3.

Pub

lishe

d st

udie

s inv

olvi

ng h

ome

rang

e es

timat

es fr

om n

ativ

e po

pula

tions

of T

. car

olin

a.

Aut

hors

(Dat

e)

# of

Tur

tles

(# o

f loc

/turtl

e)

Dur

atio

n

of st

udy

Met

hod

Hom

e R

ange

Siz

e

Estim

ate

Loca

tion

(stu

dy si

ze)

Nic

hols

193

9 12

(14)

20

yrs

M

ark-

reca

ptur

e 12

0-20

0 m

dia

m.

Long

Isla

nd, N

Y

Stic

kel 1

950

55 (3

+)

3 yr

s M

ark-

reca

ptur

e &

thre

ad

traili

ng

100

m d

iam

eter

M

aryl

and

(11

ha)

Dol

beer

196

9 ‘m

any’

of 2

70

mar

ked

1 yr

M

ark-

reca

ptur

e 76

.2 m

dia

m.

Tenn

esse

e (8

.9 h

a)

Schw

artz

&

Schw

artz

197

4

239

(4-1

8)

8 yr

s D

og c

aptu

re-r

ecap

ture

&

Rad

iote

lem

etry

1.9

ha

ave.

are

a

(1.2

-10.

2 ha

)

Mis

sour

i (22

ha)

Mad

den

1975

23

(85)

4

yrs

Rad

iote

lem

etry

♀

373

m d

iam

.;

♂ 2

84 m

dia

m.

2.12

ha

ave.

are

a

New

Yor

k

Stra

ng 1

983

8 (3

+)

3 yr

s Th

read

trai

ling

167

m d

iam

. Pe

nnsy

lvan

ia (2

9 ha

)

Schw

artz

&

Schw

artz

198

4

37 (1

1-44

) 19

yrs

D

og c

aptu

re-r

ecap

ture

&

Rad

iote

lem

etry

5.2

ha a

ve. a

rea

(0.6

-10.

7 ha

)

Mis

sour

i (22

ha)

Bay

less

198

4 6

(10+

) 56

day

s

over

2yr

s

Rad

iote

lem

etry

& th

read

traili

ng

213

m d

iam

.

1.25

ha

Virg

inia

(49.

4 ha

)

Will

iam

s &

Park

er 1

987

35 (3

+)

26 y

rs

Mar

k-re

capt

ure

♀ 1

76 m

dia

m.

♂ 1

71 m

dia

m.

Indi

ana

(72.

9 ha

)

34

Aut

hors

(Dat

e)

# of

Tur

tles

(# o

f loc

/turtl

e)

Dur

atio

n

of st

udy

Met

hod

Hom

e R

ange

Siz

e

Estim

ate

Loca

tion

(stu

dy si

ze)

Hal

lgre

n-Sc

affid

i

1986

11 (3

+)

2 yr

s M

ark-

reca

ptur

e &

thre

ad

traili

ng

97 m

dia

m.

0.2

ha a

rea

Mar

ylan

d (1

1.3

ha)

Stic

kel 1

989

103

(3+)

37

yrs

M

ark-

reca

ptur

e 14

5 m

dia

m.

♀ 1

.13

ha a

rea

♂ 1

.2 h

a ar

ea

Mar

ylan

d (1

1 ha

)

Don

alds

on &

Echt

erna

cht 2

005

13(3

0-54

) ~1

50 d

ays

Rad

iote

lem

etry

& th

read

traili

ng

1.88

ha

area

Te

nnes

see

(28

ha)

Qui

nn 2

008

14 (a

v. 6

2)

1 yr

R

adio

tele

met

ry

♀ 4

.0 h

a ar

ea

♂ 6

.7 h

a ar

ea

4.97

ha

ave.

are

a

Con

nect

icut

Cur

rent

Stu

dy

50 (a

v. 3

4-70

/yr)

4

yrs

Rad

iote

lem

etry

♀

5.5

5 ha

are

a

♂ 9

.14

ha a

rea

7.45

ha

4-yr

ave

.

Indi

ana

(35,

000

ha)

35

Appendix 1. Summary of the Eastern Box Turtle annual home ranges at nine study

sites in south-central Indiana from 2007-10. Year, sex, management class (Mngmt

Class), number in group (n), and median, mean, and standard errors of annual home range

(100% Minimum Convex Polygon; MCP) in hectares (ha). For 2007-08, the

management class represents the assigned harvest type prior to harvest implementation.

Year Sex MngmtClass n Median Area Mean Area Std Err

2007 F Clearcut 4 4.76 16.44 12.747

Control 4 1.63 1.62 0.274

GroupSelection 2 2.26 2.26 0.360

M Clearcut 4 1.59 2.03 0.540

Control 4 1.90 34.02 32.289

GroupSelection 5 2.89 3.58 1.032

2008 F Clearcut 5 3.04 3.04 0.568

Control 3 4.77 5.40 2.463

GroupSelection 2 9.28 9.28 7.185

M Clearcut 5 1.97 3.84 1.469

Control 4 4.17 49.50 46.064

GroupSelection 7 1.20 4.31 2.966

2009 F Clearcut 7 2.16 9.77 5.835

Control 7 6.57 6.69 1.712

GroupSelection 7 2.11 3.94 2.025

M Clearcut 6 2.94 3.01 0.664

Control 6 2.48 17.57 15.510

GroupSelection 8 1.85 1.99 0.405

2010 F Clearcut 7 1.64 2.11 0.641

Control 7 2.50 5.38 2.369

GroupSelection 8 2.07 3.48 1.358

M Clearcut 7 2.48 9.02 6.155

Control 7 2.20 2.97 1.041

GroupSelection 8 1.71 2.05 0.345

36

CHAPTER 2: HIBERNAL THERMAL ECOLOGY OF EASTERN BOX TURTLES

WITHIN A MANAGED FOREST LANDSCAPE

Abstract

Box turtles are being extirpated from much of their former range and remaining

populations often live in association with anthropogenically altered habitats. This is

particularly evident at the northern distributional limit of eastern box turtles (Terrapene

carolina carolina) and important over the winter months when their ability to respond to

microclimatic change is limited. Using temperature dataloggers, I studied the hibernal

microclimate of box turtles and associated habitat following timber harvests. I monitored

the body temperatures (Tb) of 38 T. c. carolina and collected detailed air and soil profile

temperatures of 12 box turtle hibernacula, 6 clearcut treatments, and 6 adjacent forested

areas during the hibernal season (winter 2009-10). I was able to partition the hibernal

season into two biologically significant thermal periods: hibernation and emergence. The

mean hibernation Tb averaged (3.28°C, SE = 0.09) and corresponded to an average depth

of 10 cm. Clearcuts were consistently colder (mean = 1.91°C) than forests (mean =

2.68°C) and hibernacula (mean = 2.77°C) during hibernation, but became the warmest

areas during emergence (mean = 9.96°C). I found that in the average clearcut, turtles

could burrow to approximately 20 cm in order to attain the average hibernation Tb or to

approximately 15 cm to attain Tb no different than those overwintering on colder,

northeast-facing slopes in the forest (mean = 2.83°C). Alternatively, I found that

southwest-facing slopes were warmer and if turtles chose to overwinter only in clearcuts

on those slopes, they could remain shallower. All but one turtle overwintered in forested

areas; however, our study suggests that timber harvests offer various microhabitats

exploitable by hibernating box turtles based on soil profile temperatures, slope aspect,

and depth of hibernation.

37

Introduction

Among all threats to the perseverance of wildlife populations, habitat loss and

alteration are considered the most pervasive and deleterious (Fahrig 2003; Gibbons et al.

2000; Lawton et al. 2001; Todd & Andrews 2008). Consequently, practices encouraging

the sustainable use of natural resources such as timber harvesting are increasingly

becoming the focus of conservation study (Fredericksen et al. 2000; Gitzen et al. 2007; Li

et al. 2000; Perison et al. 1997). A variety of vertebrate taxa (including birds, small

mammals, and some herpetofauna) benefit, at least temporarily, from the canopy

openings and clearings created by certain silvicultural techniques (Fredericksen et al.

2000; Goldstein et al. 2005; Semlitsch et al. 2009). However, other taxa (especially

amphibians) have been found to respond negatively to timber harvests (Cushman 2006;

Semlitsch et al. 2009), while many more have not been studied and their response to

timber harvests is not known. Thus, effects of timber harvests can differ both across taxa

and within species based on their changing habitat requirements throughout the year.

Habitat selection occurs during biologically significant events including mating,

nesting, and the selection of overwintering sites (Madden 1975; Spencer & Thompson

2003). While our general knowledge of habitat selection for many species is plentiful for

both mating and nesting events, there is far less information for hibernal season

(overwinter). Moreover, there is a severe dearth of information regarding the impacts on

wildlife associated with silvicultural practices during the hibernal season. For non-

migratory species, hibernal season habitat selection is critical to survival, especially for

poikilotherms whose body temperature is regulated by ambient temperature.

Herpetofauna are particularly affected by habitat alteration in that they must behaviorally

adapt to environmental flux (Johnston & Bennett 1996). Many herpetofaunal species

sustain regular cycles of dormancy to adapt to changing environmental conditions

(Gregory 1982). Cold winter conditions will cause many taxa to retreat to hibernacula

for extended periods (e.g. Squamate spp. up to 8 months, Anuran spp. up to 11 months;

Aleksiuk 1976; Zug et al. 2001). Therefore, as analysis of behavior at these hibernation

sites is equally as important as during the active season. Empirical evaluation of habitat

38

selection during the hibernal season is crucial to gain a more complete picture of the

effects of timber harvests on forest dependent wildlife species.

Eastern box turtles (Terrapene carolina carolina) are a forest-dwelling species

that are declining throughout their range (Dodd 2001; Hall et al. 1999; IDNR 2007;

Stickel 1978; Williams & Parker 1987). This species is protected in most states within its

range and its survival may be compromised by habitat proximity to anthropogenic

disturbances (Currylow et al. 2011). Box turtles select habitats based on a combination

of factors, including cover and temperature (Reagan 1974). Canopy cover influences

temperature by means of regulating light intensity, a factor known to be critical for turtles

during activity periods (Gould 1957; Rose & Judd 1975). Ground and air temperature

play key roles in the activity of box turtles, even in winter months (Congdon et al. 1989).

Eastern box turtles may hibernate for a significant proportion of the year (up to nine

months) however, much in situ work with this species involves only active season

monitoring. The studies that do examine hibernal behavior are often limited by unnatural

settings, do not address thermal environments, or are narrow in scope (few records and

lack of habitat variables such as slope aspect or canopy). Alterations of temperature due

to canopy removal and the concomitant use by box turtles have not been studied during

hibernal seasons.

Thermoregulation is ostensibly an important factor in hibernacula selection and

overwintering behavior in box turtles. Box turtles have a natural mechanism that enables

them to endure sub-zero temperatures when more than 58% of their body fluids are

frozen, with minimal deleterious effects (Costanzo & Claussen 1990). Though T. c.

carolina can survive below freezing temperatures, mortality due to prolonged exposure is

not uncommon (Claussen et al. 1991). Box turtles burrow to avoid extreme temperatures

during the hibernal season (November through April). They may burrow deeper as the

seasonal temperatures decrease (Carpenter 1957). The majority of studies have found T.

carolina to overwinter at an average depth of only five centimeters, and no more than 18

cm (Carpenter 1957; Claussen et al. 1991; Congdon et al. 1989; Dolbeer 1971; Madden

1975; Minton 2001). Depth to which turtles burrow may also depend on slope aspect.

39

Slopes are an important consideration when studying thermal profiles during the hibernal

season because slopes that face the sun low on the horizon will remain warmer than

slopes facing away from the sun. Therefore, it is important to include evaluations of

slope aspect, especially in areas completely exposed such as in timber harvests.

In this study, I expanded upon the limited knowledge pertaining to hibernal

season impacts of timber harvests on a hibernating forest ectotherm. Specifically, I

aimed to investigate whether timber harvested areas offer suitable habitat for

overwintering eastern box turtles. The goals of this study were to: (1) characterize

hibernal thermal behavior of eastern box turtles, (2) determine the available thermal

habitat in timber harvests relative to forests on various slope aspects, and (3) evaluate the

effect of timber harvests on actual and theoretical hibernal habitat use.

Study Area

The study was conducted within approximately 35,000 hectares of Morgan-

Monroe and Yellowwood State Forests in Morgan, Monroe, and Brown Counties,

Indiana. Both forests are characterized by hills and ravines of hardwood, deciduous

forests with scattered timber harvest areas. The majority of canopy species are Quercus

spp., such as montnana (chestnut oak), and Carya cordiformis and C. ovata (butternut

and shagbark hickory; Summerville et al. 2009).

Morgan-Monroe and Yellowwood State Forests are managed for multiple-uses,

including recreation, education, research, and timber harvesting. The study site was

selected because it comprises a relatively contiguous forest and population of free-

ranging box turtles, and timber harvests were recently implemented within the box turtle

habitat as part of the Hardwood Ecosystem Experiment (HEE). The HEE is a long-term

(100-yr), landscape-scale timber and wildlife research and management collaborative

designed for the study of ecological and social impacts of various silvicultural methods.

For our study, I focused on six of the nine HEE study sites, each with similar vegetative

species, slope aspects, and elevations. The six study sites encompass approximately 400

hectares each and were randomly assigned a management type: clearcut treatments (2

40

clearcuts approximately 4-hectares each) or control (no timber removal), each with three

replicates (Figure 6). The clearcuts were implemented over the winter of 2008-09 within

90-hectare centers of each unit to allow the remaining forest to act as buffer areas.

Methods

Turtle Monitoring

To locate hibernaculum sites for hibernal monitoring I used standard

radiotelemetry homing methodology. As part of a concurrent radiotelemetry study, radio

transmitters (Holohil RI-2B, Carp, Ontario, Canada; 14.5 grams each representing less

than 5% of the animal’s total body weight) were epoxied to the carapaces of 38 adult box

turtles (19♂, 19♀) throughout the the HEE sites (Figure 6). I followed turtles until they

were consistently found underground for hibernation (5 November 2009). Initiation of

hibernation was defined as the first date each turtle was consistently observed buried

underground provided that it was subsequently found at that location for at least one

week before regular tracking ceased. To represent the temperatures turtles chose over

time, I affixed temperature dataloggers, accurate to 0.5° Celsius (Thermochron iButtons,

model number DS1921G-F5, Maxim Integrated Products, Inc., Sunnyvale, California,

USA) to each turtle’s carapace prior to hibernation. Carapacial temperature

measurements have been found to correlate well with turtle core body and cloacal

temperatures (Bernstein & Black 2005; Congdon et al. 1989; do Amaral et al. 2002;

Peterson 1987). Temperature dataloggers were set to record turtle body temperatures

(Tb) every 180 minutes throughout the hibernal season. These temperatures were then

aligned with soil thermal profile temperatures (described below) to inform turtle

burrowing depth. These activities were permitted under Purdue Animal Care and Use

Protocols and amendments (PACUC 07-037).

Experimental Design and Habitat Monitoring

To document levels of hibernal microhabitats available to burrowing animals, I

monitored temperatures at multiple soil depths using thermal profile stakes (hereafter:

TPS) at 24 locations throughout the study sites. The TPS consisted of five temperature

41

dataloggers affixed at 10-cm intervals along the length of a 1.3x5x51-cm wooden stake,

and sunk into the forest floor. The profile intervals spanned from 10 cm above soil

surface (in the leaf litter at “turtle height”), at the soil surface (0 cm), and at 10, 20, and

30 cm below the soil surface (Figure 7a). I programmed the temperature dataloggers to

logging intervals of 180 minutes and they recorded soil profile temperatures throughout

the landscape for 22 weeks from 8-November 2009 through 10-April 2010.

For this study, I compared thermal environments between forested habitats

(forests) and clearcut treatments (clearcuts) to evaluate their suitability as box turtle

hibernal habitat. Twelve TPS were placed mid-slope at each of the 4-ha clearcut

treatments (six replicates of “clearcut TPS”) and adjacent forested habitats (six replicates

of “forest TPS”; Table 4). I used ArcGIS to determine the random locations of the TPS

within the designated habitats. I placed the remaining 12 TPS at selected turtle

hibernacula (Figure 7b) to characterize soil profile temperatures where turtles chose to

overwinter. Each of these “hibernacula TPS” replicates were sunk into the forest floor

within 1 m of hibernating turtles, but no closer than 0.33 m to avoid disturbing the turtle.

Hibernating turtles were radio-tracked monthly to ensure consistent proximity to

hibernacula TPS was maintained over the hibernal season. The 12 turtles associated with

hibernacula TPS were selected based on a variety of factors including their association

with clearcuts, sex, slope aspect, and elevation. Hibernacula TPS were divided equally

by sex and active season home range association with clearcuts or controls. Slope aspect

and elevation can significantly affect the amount of penetrating solar radiation, vegetative

cover, precipitation, and consequently, the temperature of a particular location (Holland

& Steyn 1975; Schulze 1975). Thus, replicates of north-to-east- and of south-to-west-

facing slopes were used to the greatest extent possible (Table 4). On all slopes,

elevations were selected to most closely match the average turtle hibernacula

(approximately 260 m).

Analyses

I analyzed thermal data at multiple levels in an attempt to characterize the

hibernal ecology of box turtles and detect specific patterns of temperature in the

42

landscape relative to clearcut and forested habitat. I processed raw logged data using R

version 2.10.1 (R Development Core Team 2009), which is capable of handling and

managing very large datasets, and calculated daily minimum, maximum, and mean

temperatures for all temperature loggers. I analyzed all temperatures weekly to

determine biologically significant periods over the season. Temperatures recorded from

each of the 38 turtles were combined to obtain an average hibernal Tb at which turtles

spend the majority of their time. To determine the depths to which turtles burrow

overwinter, Tb were compared to hibernacula TPS on specific slopes.

Overwintering microclimates throughout the landscape were determined by

various comparisons of the TPS temperatures. I tested for differences in TPS

temperatures at varying depths and slopes for each of the TPS types (clearcut, forest, and

hibernacula) across time. I used restricted maximum likelihood (REML) method for

fitting our mixed model designs for each test. I used temperature logger ID as a repeated

measures random effect with sex, slope, period, depth, and associated location as fixed or

interacting effects, depending on the scenario. Following those analyses, I conducted

Least Squares Means Tukey-Kramer post-hoc pairwise comparisons or Student’s t tests

where appropriate to detect significant differences in mean temperatures. All statistical

analyses were carried out using JMP statistical software (SAS 2008). Values were

considered significant where the P-values were less than 0.05 and differences in mean

temperature values were greater than 1°C (Δ°C > 1).

Results

Over the 22-week period, 191,200 temperatures were recorded on a variety of

slope aspects associated with clearcuts, forests, and turtles. Due to the volume of data,

many of the comparisons were statistically significant; however, the accuracy of the

temperature dataloggers (± 0.5°C) is an additional criterion that must be considered.

Here I report all statistical significance with both of these considerations in mind (i.e. P <

0.05 and Δ°C > 1).

43

Temporal analysis of all TPS temperatures revealed two biologically significant

time periods within the 22-weeks of monitoring: hibernation and emergence. Mean

temperatures of these periods are significantly different (F1, 45 = 1059, P < 0.001, Δ°C =

6.56) and are divided by the time at which inversion of soil and surface temperature

occurs (point of inversion). For example, early in the season the coldest hibernacula

temperatures were found at the surface and progressively warmed at increasing depths

(Figure 8). However, between the 17th and 18th week of monitoring (28 February – 7

March 2010), that trend reversed and the warmest temperatures were found at the surface.

I refer to the thermal period between weeks 2 and 17 as “hibernation” and between weeks

18 and 22 as “emergence” (Figure 8).

Box Turtle Thermal Behavior

All 12 TPS-associated turtles remained within 3 m of their hibernacula TPS (i.e.,

no turtles made significant movements over the hibernation period from their last known

location the previous fall). Most turtles (n = 34) chose hibernacula between 14 October

and 29 October 2009 and the vast majority of turtles (97%) overwintered in forested

habitats. A single female turtle (706F) overwintered within an unmonitored 2.56-ha

harvest opening associated with a separate aspect of the HEE.

Mean hibernation Tb (3.28°) of all turtles differed significantly from emergence

Tb (9.32°C; F1, 72 = 1297, P < 0.001, Δ°C = 6.04; see Appendix ). Turtle 706F

maintained Tb values that were comparable but warmer (ave = 3.72°C) than the mean

hibernation Tb. In addition, the mean depth of hibernation for all turtles averaged slightly

less than 10 cm. Turtles began to decrease their depths and emerge corresponding to

higher temperatures after the point of inversion (28 February – 7 March 2010). While I

found no statistically significant differences in mean Tb between the sexes over the

hibernal season, several trends in those data were observed. Females averaged slightly

warmer Tb (3.34°C) than males (3.22°C) during the hibernation period. Moreover,

differences between sexes were even more striking for the subset of 12 turtles in

monitored hibernacula. Males selected hibernation Tb matching depths just below the

soil surface (2.55°C) with the shallowest overwintering turtle consistently above the soil

44

surface (turtle number 605M, Tb ave = 1.81°C). Monitored females, on the other hand,

chose Tb matching depths at 10 cm (3.51°C) with the deepest burrowing to 20 cm (turtle

number 906F, Tb ave = 4.44°C). These two extreme cases constitute the minimum and

maximum mean hibernation Tb, respectively (see Appendix ).

Eight of the 38 turtles were not used in analyses involving slopes. Four of these

turtles did not meet the criteria for determining if a hibernaculum site was selected before

tracking ceased and four overwintered in flat locations such as hilltops or creek-beds. No

turtles chose to overwinter on north-facing slopes and these slopes were not monitored.

Tb varied somewhat by slope during both hibernation (P = 0.6129) and emergence

periods (P = 0.2623; Table 5). Before the point of inversion at week 17, the overall

warmest slope aspect was southeast (mean at all depths = 3.49°C) and the overall coldest

was northeast (mean at all depths = 2.47°C). Turtles overwintering on these warmer,

southeast-facing slopes did not burrow as deeply as other hibernating turtles, but were

able to remain as warm (mean Tb = 3.31°C). The mean hibernation Tb (3.28°C) was

found just below the surface on southeast-facing slopes (mean=3.06°C at a depth of 0

cm) and was not significantly different from the mean Tb found deeper on most other

slopes (mean = 3.33°C at a depth of 10 cm). Turtles overwintering on colder, northeast-

facing slopes also did not burrow as deeply as most other turtles, but the colder slope

aspect resulted in relatively cold mean Tb (mean = 2.65°C). After the point of inversion,

the warmest slope aspects were south (mean at all depths = 9.28°C) and southwest (mean

at all depths = 9.25°C) while the coldest remained northeast (mean at all depths =

8.29°C). Interestingly, the turtles that hibernated shallowly on both southeast- and

northeast-facing slopes emerged sooner than the average on other slopes. Additionally,

those turtles who overwintered on southwest-facing slopes averaged emergence Tb that

matched soil depths between 0 and 10 cm (Tb mean = 9.00°C, 0 cm = 10.60°C, 10 cm =

8.52°C), suggesting that they were still below the surface during the emergence period

despite those slopes being among the warmest.

45

Microclimates of Forests vs. Clearcuts

The thermal habitat in timber harvested versus forested areas was evaluated by

comparing mean temperatures from TPS within the clearcuts (n = 6), the forest (n = 6),

and at turtle hibernacula (n=12). There was no difference between mean temperatures of

TPS habitat or slope comparisons during the entire 22-week hibernal season (F2, 21 = 1.7,

P = 0.2088, Δ°C = 0.36). However, when separated by hibernation and emergence

periods, the clearcuts maintained more extreme daily temperatures. During hibernation,

the range of temperatures were significantly greatest in clearcuts (F 2, 47 = 9.32, P =

0.0004) meaning these areas were more variable in temperature. However, clearcuts

were consistently colder (mean from all depths = 1.91°C) than forests (mean from all

depths = 2.68°C) and hibernacula (mean at all depths = 2.77°C) during hibernation (F 2, 21

= 9.60, P = 0.0011), but were warmest during emergence (mean from all depths =

9.96°C; F 2, 21.07 = 6.70, P = 0.0056; Table 6). Although ambient (+10 cm) temperatures

during the hibernation period were nearly identical in all locations, comparable soil

temperatures in clearcuts were found approximately 10 cm deeper than in forests and

hibernacula (i.e., clearcut hibernation temperatures at a depth of 10 cm were more similar

to forest hibernation temperatures at 0 cm; Figure 9). It is interesting to note that during

the emergence period, hibernacula locations were generally cooler than other locations at

all depths, and significantly so from treatments on most slopes (see Appendix ).

Slope aspect influenced microclimates in clearcuts and forests (Table 6; see also

Appendix ). During hibernation, southwest-facing slopes in forests were the warmest

overall (mean from all depths = 3.16°C), but during emergence, southwest-facing slopes

in clearcuts became the warmest (mean from all depths = 10.50°C). On average, the

coldest slopes were northeast facing during hibernation (mean from all depths = 2.11°C)

and northwest facing during emergence (mean from all depths = 8.42°C). Nonetheless,

when depth is taken into account, northeast-facing slopes showed the greatest differences

in mean temperatures across habitats (from +10 cm during hibernation at -0.88°C to +10

cm during emergence at 11.02°C; see Appendix ).

46

Discussion

Forest management practices change the vegetative structure and local

environmental conditions, which in turn may alter species use of available habitat

(Renken et al. 2004). Many forest dwelling vertebrates (both endothermic and

poikilothermic alike) will preferentially use certain types of available habitat at different

times throughout the year for thermoregulation, nesting, and dormancy (Madden 1975;

Schwartz & Schwartz 1974). The current study provides key insights into the hibernal

thermal behavior of eastern box turtles and the microclimates of habitats within timber-

harvested areas versus those within adjacent forests.

Several general patterns have emerged from TPS within clearcuts, adjacent

forests, and at turtle hibernacula. First, the emergence of box turtles was correlated with

an inversion of surface and deep soil temperatures. Once the point of inversion occurs,

turtle hibernacula are no longer warmer than soil surface temperatures. Previous studies

attribute rising air, surface, and rough estimates of subsurface temperatures as the triggers

for box turtles to emerge in the spring (Bernstein & Black 2005; Grobman 1990). Our

data suggests proximity to the surface is also a key factor to timing of emergence.

Turtles that burrowed deeper during winter months emerged later in the spring.

Second, nearly all turtles chose hibernacula that were in forested habitats. Only a

single radiotelemetered turtle overwintered within a HEE-associated harvest opening.

The question of whether T. c. carolina will use forest openings such as clearcuts during

the hibernal period is central to this project. It could be argued that few turtles

overwintered within clearcuts because the total area of openings was small relative to that

of forested habitat and thus, not part of the turtles’ normal home range. While the

treatments do represent a relatively small proportion of the overall study site (<1.5%),

associated radiotelemetry data clearly demonstrates that harvest openings are used by

many of these same turtles during the turtle’s active season (averaging 8.2% of their

home ranges; Currylow et al., in prep). Therefore, the lack of overwintering sites within

treatments may reflect habitat selection based on simple energetics.

47

With little leaf litter or canopy cover to buffer harsh weather, the microclimate of

the clearcuts often exhibited temperature extremes that overwintering turtles were

expected to avoid. Freezing temperatures are known to cause mortality in even hearty,

freeze-tolerant taxa such as frogs and salamanders, as well as box turtles (Carpenter

1957; Metcalf & Metcalf 1979; Storey & Storey 1986). During intermittent warm

periods, however, hibernal soil temperatures in clearcuts temporarily increased above

those found in adjacent, uncut forests. Higher soil temperatures mid-winter has been

implicated in the premature emergence and subsequent freezing death of overwintering

turtles (Neill 1948; Schwartz & Schwartz 1974; Ultsch 2006). Nearly all turtles in this

study (37 of the 38) chose hibernacula in forested areas where forest debris such as leaf

litter was noted to be greater than in clearcuts. Dolbeer (1971) noted that turtles selected

areas with a thick mat of leaf litter and rotting logs for hibernacula. Based on soil profile

data among clearcuts and forests, turtles overwintering in a clearcut would need to

burrow an average of 10 additional centimeters to achieve the warmer Tb.

The third general pattern that emerged from temporal analyses of temperatures

was that most turtles chose temperatures of 3.28°C for hibernation. This Tb corresponded

to a depth of approximately 10 cm, which is within the range (5-18 cm) found in other

studies (Carpenter 1957; Claussen et al. 1991; Congdon et al. 1989; Dolbeer 1971;

Madden 1975; Minton 2001). Interestingly, I found that females maintained slightly

warmer Tb than males and generally burrowed deeper throughout hibernation. Many

males burrowed to just below the soil surface with only leaf litter shielding them from

harsh winter weather conditions. It is unclear as to whether this observation is due to

variation caused by slope aspect. One explanation is that certain adult males could be

physiologically more tolerant of the cold, although studies on hatchling turtles showed no

sex differences in cold tolerance (Costanzo et al. 1995; Packard & Janzen 1996). A

blood chemistry panel from a subset of turtles in the present study showed that males

generally had higher freeze-resistant glucose levels than females and that turtle 605M

(who was at the surface for a majority of the hibernal season) had comparable levels to

other males (Kimble et al., unpublished data). In contrast, females undergoing follicle

development may select warmer sites to speed the process or because their increased

48

mass would cause them to recover from freezing temperatures more slowly (Shine 1980).

Despite numerous laboratory studies on freeze tolerance in this species, the reported sex

difference herein is novel and warrants further investigation.

Slope aspect appears to be an important habitat characteristic for many burrowing

animals during the hibernal season. Black Rat Snakes and Eastern Massasauga

Rattlesnakes in Ontario prefer to hibernate on south-facing slopes that remain warmer

and thaw earlier, likely ameliorating the effects of freezing winter temperatures (Harvey

& Weatherhead 2006; Prior & Weatherhead 1996). Similarly, toads in the Pacific

Northwest chose to inhabit south-facing slopes and burrow to just below the frost line

(Bull 2006). Yellow-bellied marmots in Colorado generally choose burrows on either

southwest- or northeast-facing slopes year-round, but choose those with deep, insulating

snow cover overwinter (Svendsen 1976). In contrast, Claussen et al. (1991) found that T

c. carolina in Ohio’s woodlands prefer nearly level ground or west-facing slopes for

hibernacula, but I found no such trend among the 38 turtles in this study. However, I did

observe patterns in the burrowing behavior (depth of hibernacula) depending on the slope

of the selected hibernaculum site. As with the aforementioned studies, many of our

animals burrowed deeper to reach warmer temperatures overwinter. However, the

conflicting behavior I noted on the colder, northeast-facing slopes is an important

observation, as the temperatures available in the clearcuts were overall equally as cold.

The clearcuts did offer temperatures most often used by overwintering turtles, but at

greater depths (depending on slope) than forested areas and hibernacula. Therefore, these

areas could theoretically be inhabited by burrowing animals during the winter months.

Forest floor temperatures have been shown to affect the burrowing activity of

small mammals, amphibians, reptiles, and invertebrates (Byers 1984; Landry-Cuerrier et

al. 2008; Vernberg 1953). Temperatures collected in this study can be used to predict the

hibernal use of clearcuts. If overwintering animals choose to use clearcuts for

hibernaculum sites, they must behaviorally adapt as found in some amphibians (Storey &

Storey 1996). Turtles must burrow twice as deep (20 cm) to attain a mean Tb of 3.28°C,

or tolerate the colder hibernation temperatures of 2.83°C (at 15 cm). Alternatively, they

49

could choose to overwinter in clearcuts only on warmer slopes (such as southwest facing)

and burrow 10 cm to attain the mean hibernation temperature.

Turtle 706F was the only turtle to overwinter in a timber harvest opening. This

female was able to maintain above average hibernation temperature, despite being in an

opening and on a northeast-facing slope. Using the temperatures obtained from TPS that

were placed in other northeast-facing treatment slopes, I determined that this female

would have had to burrow to depths greater than 30 cm to attain her hibernation

temperatures in that habitat. Even the northeast-facing slopes of forested habitats only

offered temperatures comparable to her mean at depths of nearly 20 cm. A comparison

of 706F daily mean temperatures to corresponding TPS suggests this turtle regulated

body temperature by rising to the surface on warmer days and burrowing deeper on

colder days. These depth adjustments are frequently seen in the T. c. triunguis

subspecies, which burrows deeper as winter temperatures decrease (Carpenter 1957; do

Amaral et al. 2002). Still, I did not observe this behavior to such extremes in any of the

12 hibernacula monitored turtles or the remaining 25 turtles until the emergence period.

Data from this and other studies indicate that site fidelity may play a role in

hibernacula selection. Cook (2004) observed that several individuals exhibited

hibernacula site fidelity with inter-hibernacula changes of less than 100 m over

successive years. Analysis of the concurrent radiotelemetry study data of the same turtles

herein indicate that in 2010 turtles chose overwinter locations averaging 123 m from the

2009 site (Appendix C). Most turtles appeared to choose sites within 61 meters of their

2009 hibernacula (median = 41 m, min = 5.8 m, max = 1801 m). Thus, it is unlikely that

turtles would indiscriminately return to the exact location of a previous hibernacula if

habitat alteration made it undesirable. Instead, the animal could choose a more desirable

site adjacent to that location. None of the turtles appeared to choose 2010 overwintering

locations within the treatments, although some were relatively close. Turtle 706F was

last located in 2010 within 16 m of the edge of the harvest opening she hibernated in

previously; and turtle 906F, which was the turtle that maintained the warmest hibernation

temperatures in 2009-10, was within 20 m of a clearcut treatment in October 2010.

50

Management Implications

The data herein suggest that small-scale timber harvests techniques used in the

Midwest have little effect on Eastern Box Turtles during the winter months. The

microclimates available in these timber-harvested habitats are within the range used by

hibernating box turtles, but are generally found at deeper depths. The typical harvest size

(0.5 - 5-ha) is small enough in proportion to animal home ranges that another habitat

could be selected for hibernacula if desired. However, the slope on which the timber

harvest is implemented may have a profound effect on other burrowing animals. A

variety of taxa use south facing slopes for overwintering sites, and I found southwest-

facing slopes to be the warmest over the winter months. Yet, temperatures in clearcuts

were more variable than in forested habitats and this may cause inconsistency in the

warmer temperatures generally offered on south-facing slopes. In contrast, these

temperature fluctuations may make the generally colder and less desirable north-facing

slopes more desirable or at least, more tolerable. If timber harvests are to be

implemented, I suggest they be done over the winter months, remain relatively small, and

placed on a variety of slope aspects to mediate their overall impact on forest-dwelling

wildlife.

Acknowledgements

I would like to thank S. Johnson for her dedicated and hard work in the field. I

would also like to thank the Williams lab group and two anonymous reviewers for review

comments on earlier versions of this manuscript. This paper is a contribution of the

Hardwood Ecosystem Experiment, a partnership of the Indiana Department of Natural

Resources (IDNR), Purdue University, Ball State University, Indiana State University,

Drake University, and The Nature Conservancy. Funding for the project was provided by

the Indiana Department of Forestry Grant #E-9-6-A558 and IDNR Division of Fish and

Wildlife, Wildlife Diversity Section, State Wildlife Improvement Grant #E2-08-WDS15.

Research activities associated with this project fall under the Scientific Purposes Licenses

09-0080 & 10-0083.

51

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56

Tabl

e 4.

Num

ber a

nd lo

catio

n of

tem

pera

ture

dat

alog

gers

in h

arve

st o

peni

ngs (

H) a

nd fo

rest

ed h

abita

ts (F

). S

lope

asp

ect

(NW

, SE,

etc

.) re

pres

ents

the

slop

e fo

r whi

ch th

e lo

gger

was

ass

igne

d or

that

the

over

win

terin

g tu

rtle

chos

e.

Slop

e A

spec

t

N

W

NE

E SE

S

SW

W

N

/A

To

tal

H

FH

FH

FH

FH

F

HF

HF

T

urtle

38

7

1 5

2

4

3

2

6 8

TPS

12

3 2

1

3

2

1

Hib

erna

culu

m T

PS

12

2

3

1

2

1

3

57

Table 5. Mean body temperatures (Tb) and standard errors for all turtles at

hibernation (Hib) and emergence (Emerg). “Unknown” slopes indicate turtles did not

select hibernacula by the final tracking date. The 12 turtles associated with hibernaculum

Thermal Profile Stakes.

Hibernaculum

Slope

# of records Hibernation Tb

Mean (°C) &

SE

Emergence Tb

Mean (°C) & SE

Northeast 7,038 2.83 0.20 8.58 0.22

East 2,346 3.20 0.35 9.20 0.37

Southeast 4,692 3.31 0.25 9.38 0.26

South 3,519 3.21 0.29 9.82 0.30

Southwest 2,346 3.23 0.35 9.00 0.37

West 7,039 3.23 0.20 9.63 0.22

Northwest 8,211 3.52 0.19 9.09 0.20

Flat 4,692 3.34 0.25 9.33 0.26

Unknown 4,692 3.61 0.25 10.11 0.26

Total Hib:34,048

Emerg:10,527

3.28 0.09 9.32 0.09

Select 12 Total H:10,752/E:3,325 3.10 0.16 9.00 0.17

58

Tabl

e 6.

Mea

n Th

erm

al P

rofil

e St

ake

tem

pera

ture

s (°C

) and

stan

dard

err

or fr

om a

ll de

pths

com

bine

d du

ring

hibe

rnat

ion

and

emer

genc

e th

erm

al p

erio

ds.

Tem

pera

ture

s are

sepa

rate

d by

hab

itat t

ypes

(for

ests

, hib

erna

cula

, and

cle

arcu

ts) a

nd b

y sl

ope

aspe

cts.

Star

red

(*) v

alue

s are

sign

ifica

ntly

diff

eren

t (P

< 0.

05 a

nd Δ

°C >

1) f

rom

eac

h ot

her/o

ther

s acr

oss h

abita

t typ

es fo

r ass

ocia

ted

ther

mal

per

iod

and

slop

e as

pect

. To

tal m

ean

valu

es a

re re

porte

d fo

r eac

h ha

bita

t typ

e at

the

botto

m o

f the

tabl

e.

Hib

erna

tion

Em

erge

nce

Slop

e n

For

ests

M

ean

& S

E

Hib

erna

cula

Mea

n &

SE

Cle

arcu

ts

Mea

n &

SE

Fore

sts

Mea

n &

SE

Hib

erna

cula

Mea

n &

SE

Cle

arcu

ts

Mea

n &

SE

NW

11

,736

.

. 2.

68

0.12

.

. .

. 8.

42

0.14

.

.

NE

46

,945

2.

44

0.17

2.

49

0.14

1.

53

0.14

8.

72

0.18

8.

00*

0.15

9.

42*

0.15

E

3,52

8 2.

24

0.10

.

. .

. 9.

20

0.17

.

. .

.

SE

5,85

8 .

. 3.

49

0.06

.

. .

. 8.

60

0.11

.

.

S 11

,734

.

. 2.

92

0.12

.

. .

. 9.

28

0.14

.

.

SW

35,1

79

3.16

0.

32

2.60

0.

45

2.29

0.

26

9.19

0.

33

9.36

0.

46

10.5

0 0.

27

W

23,4

60

2.65

0.

31

2.81

0.

18

. .

8.79

0.

33

9.10

0.

19

. .

Tota

l 13

8,44

0 2.

69

0.17

2.

77

0.12

1.

91

0.17

8.

94

0.18

8.

71

0.12

9.

96*

0.18

59

Figure 6. Study Site Map. Map of Indiana with study area in Morgan, Monroe, and

Brown Counties outlined (inset) and the six study sites (3 clearcut treatment sites and 3

control sites) as part of the Hardwood Ecosystem Experiment in south-central Indiana.

All radio-telemetered turtle hibernacula are indicated as dark dots.

60

Figure 7. TPS Setup and Arrangement. Schematic of thermal profile stakes (TPS)

with temperature loggers affixed at 10-cm increments (not to scale). The TPS recorded

the microclimate through the hibernal season (hibernation and emergence periods).

Temperatures collected from temperature loggers at each depth were matched to turtle

temperatures (Tb) in order to inform the depth to which turtles hibernated and when they

emerged (verified by radiotelemetry) (a). A subset of TPS and turtle hibernacula physical

locations with relation to the management types (clearcut treatment and control) (b).

b.

a.

61

-10-5051015

Temp C

12

34

56

78

910

1112

1314

1516

1718

1920

2122

Figu

re 8

. H

iber

natio

n Te

mpe

ratu

res.

Mea

n hi

bern

acul

a te

mpe

ratu

res r

ecor

ded

by w

eek

at v

ario

us d

epth

s (+1

0, 0

, -10

, -

20, &

-30)

and

mea

n tu

rtle

body

tem

pera

ture

s. F

igur

e ill

ustra

tes t

he p

oint

of i

nver

sion

(bet

wee

n 23

Feb

ruar

y an

d 7

Mar

201

0),

dem

arca

ting

the

hibe

rnat

ion

perio

d (w

eeks

2 th

roug

h 17

) and

em

erge

nce

perio

d (w

eeks

18

thro

ugh

22).

See

text

for d

etai

ls

and

furth

er d

escr

iptio

n.

Hib

erna

tion

Emer

genc

e

Poin

t of

Inve

rsio

n

Tim

e (w

eeks

)

Temperature °C

62

Figure 9. Habitat Temperatures by Depth. Mean location TPS temperatures (°C) by

depth (centimeters) during the hibernation and emergence periods. Temperatures found

at hibernacula and forests were not significantly different at varying depths. However,

temperatures found in treatments were significantly colder (hibernation period) or

warmer (emergence period) at nearly all depths.

Clearcut Forest Hibernacula

63

Appendix 2

Average body temperatures (Tb) of 38 adult eastern box turtles during hibernation and

emergence (sorted by sex, then hibernation temperature). The mean values are totaled at

the bottom of the table. Starred (*) individuals are the select 12 associated with

hibernacula TPS. The four turtles who did not select hibernacula by the time tracking

ceased have “unknown” slopes.

n

Hibernation Tb Emergence Tb

ID# & Sex Slope Mean (°C ) & SE Mean (°C ) & SE

1206F S 1173 2.36 0.12 9.66 0.22

506F E 1173 2.53 0.12 9.17 0.22

800F flat 1173 2.70 0.12 8.74 0.22

1357F* NE 1173 2.79 0.12 7.36 0.22

1403F flat 1173 3.03 0.12 10.09 0.22

714F SW 1173 3.13 0.12 9.27 0.22

1252F SE 1173 3.14 0.12 9.32 0.22

100F SE 1173 3.19 0.12 10.04 0.22

1360F* NW 1173 3.30 0.12 7.07 0.22

1455F* SW 1173 3.32 0.12 8.77 0.22

900F* W 1171 3.35 0.12 9.86 0.22

885F unknown 1173 3.54 0.12 10.69 0.22

503F unknown 1173 3.59 0.12 8.74 0.22

706F NE (in Tx) 1173 3.71 0.12 8.65 0.22

680F NW 1173 3.72 0.12 9.34 0.22

1602F* W 1176 3.78 0.12 9.98 0.22

603F flat 1173 3.83 0.12 8.84 0.22

880F unknown 1173 3.93 0.12 10.53 0.22

906F* S 1173 4.44 0.12 10.25 0.22

605M* NE 1173 1.85 0.12 10.02 0.22

1350M* NE 1173 2.32 0.12 7.66 0.22

64

n

Hibernation Tb Emergence Tb

ID# & Sex Slope Mean (°C ) & SE Mean (°C ) & SE

406M* W 1173 2.58 0.12 9.83 0.22

615M* NW 1173 2.71 0.12 10.28 0.22

806M W 1173 2.78 0.12 9.52 0.22

1100M* S 1173 2.86 0.12 9.46 0.22

704M NE 1173 2.97 0.12 8.60 0.22

402M* SE 1173 3.07 0.12 8.57 0.22

904M W 1173 3.14 0.12 8.77 0.22

500M NE 1173 3.30 0.12 9.29 0.22

1150M NW 1173 3.34 0.12 9.05 0.22

504M unknown 1173 3.42 0.12 10.39 0.22

708M NW 1173 3.67 0.12 8.38 0.22

814M NW 1173 3.75 0.12 9.40 0.22

700M W 1173 3.79 0.12 9.71 0.22

848M flat 1173 3.81 0.12 9.67 0.22

1207M SE 1173 3.86 0.12 9.60 0.22

1253M E 1173 3.86 0.12 9.23 0.22

607M NW 1173 4.09 0.12 10.25 0.22

65

App

endi

x 3

Mea

n te

mpe

ratu

res a

nd st

anda

rd e

rror

s (SE

) rec

orde

d fr

om e

ach

dept

h al

ong

TPS

durin

g th

e hi

bern

atio

n an

d em

erge

nce

perio

ds.

Tem

pera

ture

s are

sepa

rate

d by

stak

e ha

bita

t typ

es (f

ores

ts, h

iber

nacu

la, &

cle

arcu

ts) a

nd b

y sl

ope

aspe

cts.

Sta

rred

(*) v

alue

s are

sign

ifica

ntly

diff

eren

t (P

< 0.

05 a

nd Δ

°C >

1) o

f mea

n va

lues

acr

oss h

abita

ts (f

ores

ts, h

iber

nacu

la, &

cle

arcu

ts) f

or a

ssoc

iate

d

ther

mal

per

iod

(hib

erna

tion/

emer

genc

e), s

lope

asp

ect,

and

dept

h.

H

iber

natio

n E

mer

genc

e

Slop

e D

epth

#

of

Rec

ords

For

ests

M

ean

& S

E

Hib

erna

cula

Mea

n &

SE

Cle

arcu

ts

Mea

n &

SE

Fore

sts

Mea

n &

SE

Hib

erna

cula

Mea

n &

SE

Cle

arcu

ts

Mea

n &

SE

NE

10

9387

-0

.56

0.33

-1

.17

0.27

-0

.80

0.27

11.1

5 0.

52

10.2

5*0.

43

11.7

1*0.

43

0 93

90

0.89

0.33

2.

01*

0.27

0.

800.

279.

88

0.52

8.

37*

0.43

10

.00

0.43

-10

9388

3.

460.

33

3.40

0.27

1.

73*

0.27

7.92

0.

52

7.41

*0.

43

8.77

*0.

43

-20

9390

4.

070.

33

3.94

0.27

2.

77*

0.27

7.41

0.

52

7.08

*0.

43

8.63

*0.

43

-30

9390

4.

330.

33

4.27

0.27

3.

16*

0.27

7.24

0.

52

6.89

*0.

43

7.98

*0.

43

E

10

1176

-0

.81

0.47

.

. .

. 11

.64

0.74

.

. .

.

0 Fa

iled

. .

. .

. .

. .

. .

. .

-10

1176

3.

420.

47

. .

. .

8.07

0.

74

. .

. .

-20

1176

4.

110.

47

. .

. .

7.89

0.

74

. .

. .

-30

Faile

d .

. .

. .

. .

. .

. .

.

SE

10

1172

.

. -0

.22

0.47

.

. .

. 11

.01

0.74

.

.

0 11

72

. .

3.06

0.47

.

. .

. 8.

930.

74

. .

66

H

iber

natio

n E

mer

genc

e

Slop

e D

epth

#

of

Rec

ords

For

ests

M

ean

& S

E

Hib

erna

cula

Mea

n &

SE

Cle

arcu

ts

Mea

n &

SE

Fore

sts

Mea

n &

SE

Hib

erna

cula

Mea

n &

SE

Cle

arcu

ts

Mea

n &

SE

-10

1172

.

. 4.

460.

47

. .

. .

7.96

0.74

.

.

-20

1170

.

. 4.

780.

47

. .

. .

7.55

0.74

.

.

-30

1172

.

. 5.

380.

47

. .

. .

7.51

0.74

.

.

S

10

2346

.

. -0

.33

0.33

.

. .

. 11

.90

0.52

.

.

0 23

46

. .

1.91

0.33

.

. .

. 9.

580.

52

. .

-10

2346

.

. 3.

720.

33

. .

. .

8.83

0.52

.

.

-20

2348

.

. 4.

340.

33

. .

. .

8.24

0.52

.

.

-30

2348

.

. 4.

970.

33

. .

. .

7.87

0.52

.

.

SW

10

7035

-0

.22

0.33

-1

.06

0.47

-0

.22

0.27

11.5

0 0.

52

12.0

00.

74

12.3

00.

43

0 70

35

2.26

*0.

33

0.88

0.47

0.

880.

279.

09*

0.52

10

.60

0.74

11

.31

0.43

-10

7035

4.

340.

33

3.69

0.47

2.

69*

0.27

9.22

0.

52

8.52

*0.

74

9.93

*0.

43

-20

7038

4.

390.

33

4.37

0.47

3.

790.

278.

16

0.52

8.

010.

74

9.65

*0.

43

-30

7036

5.

010.

33

5.14

0.47

4.

290.

277.

97

0.52

7.

710.

74

9.32

*0.

43

W

10

4690

-0

.56

0.47

-0

.80

0.27

.

. 11

.15

0.74

11

.83

0.43

.

.

0 46

93

2.15

0.47

1.

470.

27

. .

9.29

0.

74

9.57

0.43

.

.

-10

4693

3.

450.

47

3.75

0.27

.

. 8.

28

0.74

8.

400.

43

. .

-20

4691

3.

960.

47

4.47

0.27

.

. 7.

85

0.74

7.

940.

43

. .

-30

4693

4.

240.

47

5.14

0.27

.

. 7.

41

0.74

7.

750.

43

. .

67

H

iber

natio

n E

mer

genc

e

Slop

e D

epth

#

of

Rec

ords

For

ests

M

ean

& S

E

Hib

erna

cula

Mea

n &

SE

Cle

arcu

ts

Mea

n &

SE

Fore

sts

Mea

n &

SE

Hib

erna

cula

Mea

n &

SE

Cle

arcu

ts

Mea

n &

SE

NW

10

2342

.

. -0

.80

0.33

.

. .

. 11

.05

0.52

.

.

0 23

49

. .

1.67

0.33

.

. .

. 8.

570.

52

. .

-10

2349

.

. 3.

440.

33

. .

. .

7.71

0.52

.

.

-20

2349

.

. 4.

220.

33

. .

. .

7.53

0.52

.

.

-30

2347

.

. 4.

860.

33

. .

. .

7.26

0.52

.

.

68

Appendix 4

Pairwise comparisons of mean distances between turtle hibernacula since 2007 (‘07) as

part of a radiotelemetry study at the Hardwood Ecosystem Experiment in south-central

Indiana. Turtles often returned to locations used previously but not necessarily

consecutively.

Turtle ID ‘07 to ‘08 ‘07 to ‘09 ‘07 to ‘10 ‘08 to ‘09 ‘08 to ‘10 ‘09 to ‘10

402M 9.22 247.16 41.00 250.24 34.53 234.83

404F 55.00 . . . . .

406M . 3062.80 . . . .

500M . 155.72 146.29 . . 9.43

503F 544.82 55.04 60.03 580.55 354.22 6.40

504M 36.50 54.57 20.12 25.50 36.12 44.28

506F . 12.73 11.05 . . 22.36

603F . 38.08 98.90 . . 75.24

605M . 483.92 398.53 . . 91.02

607M . 42.54 34.01 . . 9.22

615M . . . . . 47.10

680F . . . . . 155.13

700M . . . . . 47.17

704M 39.56 47.27 55.03 10.82 15.65 13.93

706F 88.84 89.99 57.04 5.00 36.06 39.05

708M 45.54 166.00 156.42 132.65 124.48 11.00

787F . . . . . 13.89

800F . 12.04 20.62 . . 18.44

806M . 85.00 87.09 . . 89.05

814M . . . . . 132.62

848M . . . . . 5.83

880F . . . . . 97.05

885F . . . . . 538.03

69

Turtle ID ‘07 to ‘08 ‘07 to ‘09 ‘07 to ‘10 ‘08 to ‘09 ‘08 to ‘10 ‘09 to ‘10

900F . 236.14 227.73 . . 37.58

904M . 69.63 43.01 . . 22.36

906F 200.81 58.05 35.23 230.78 213.56 26.63

908M . 71.70 9.22 . . 23.60

1206F . . . . . 129.31

1207M . . . . . 10.44

1252F . . . . . 8.54

1253M . . . . . 47.43

1350M . . . . . 1800.64

1357F . . . . . 43.01

1360F . . . . . 43.86

1455f . . . . . 264.70

1602F . . . . . 24.70

Average 127.54 277.13 88.31 176.51 116.37 123.06

St. Dev. 178.49 704.67 99.43 205.44 126.37 313.89

Median 50.27 70.67 55.03 132.65 36.12 41.03

PUBLICATION

70

PUBLICATION

71

72

73

74

75

76