Measuring Circadian Entrainment in Five Species of LemursM. S. Rea1, M. G. Figueiro1, G. E. Jones1, K. E. Glander 2

1 Lighting Research Center, Rensselaer Polytechnic Institute, Troy, NY 12180-33522 Department of Evolutionary Anthropology, Duke University, Durham, NC 27708-0383

© 2014 Rensselaer Polytechnic Institute. All rights reserved.

SponsorsLighting Research CenterMargot Marsh Biodiversity Foundation

BackgroundThere are nearly 100 species of lemurs in Madagascar, each of different sizes, colorations, and diets (Mittermeier

et al. 2010). Lemur species also differ in terms of their photic niche, some are nocturnal, some are diurnal and someare cathemeral (active both day and night). Very little is known, however, about the relationship between lemurbehavior and their 24-hour light-dark exposure patterns. Certainly circadian entrainment, relating proximate light-darkexposure and activity-rest patterns, has never been measured in lemurs (Rea et al. 2014).

MethodsFour individuals each of five species of lemurs (Eulemur mongoz, Lemur catta, Propithecus coquereli, Varecia

rubra and Varecia variegata variegata) housed at the Duke Lemur Center (DLC) in Durham, North Carolina, were fittedwith a Daysimeter-D pendant that contained light and accelerometer sensors (Figure 1). The DLC is a unique facility,not only because it houses over 15 species of lemurs, but also because most of the animals may roam at will betweenthe carefully maintained DLC facility and a large outdoor reserve.

Circadian entrainment can be quantified using phasor analysis where the synchrony between the measuredproximal light-dark exposure pattern and the measured activity-rest pattern is determined (Rea et al. 2010). Phasoranalysis provides two outcome measures — phasor magnitude is the degree to which the light-dark and activity-restpatterns are correlated and phasor angle reflects the temporal, or phase relationship, between the two patterns.

Poster P281SRBR 2014 — 14th Biennial MeetingSociety for Research on Biological Rhythms

Big Sky, MTJune 2014

Propithecus coquereliCoquerel’s sifaka

Eulemur mongozMongoose lemur

Lemur cattaRing-tailed lemur

Varecia variegata variegataVariegated black-and-white

ruffed lemurVarecia rubra

Red ruffed lemur

The Daysimeter-D measures proximate light-dark exposure patterns and associated activity-rest patterns and records data using on-board memory. The Daysimeter-Ds were mounted on collars as pendants (see subject photos, Figures 2-6).

ResultsCommon as well as species-specific light exposure and behavior patterns were observed (Figures 2a-6b).

• All five species were more active between sunrise and sunset.• All five species demonstrated an anticipatory increase in their pre-sunrise activity that peaked at sunrise with

all but V. rubra showing a reduction within an hour.• All five species reduced activity during mid-day.• Four of the five species stayed active after sunset, but P. coquereli began reducing their activity about two

hours before sunset.• Average phasor magnitudes and angles are included in each panel (Figures 2a-6b). Like normal humans

working dayshifts (i.e., not night- or rotating-shift humans), the lemurs were entrained to their diurnal photicniche (phasor magnitudes > 0.3). Unlike normal humans that have positive phasor angles, however, theunrestricted lemurs exhibit negative phasor angles which result from their advanced activity-rest patternsrelative to their light-dark exposure patterns. Interestingly, the two L. catta restricted to the indoor environmentexhibited positive phasor angles.

• Two animals of one species (L. catta) were restricted to indoor environment while the other two were not(Figure 6b). Phasor magnitudes were nearly identical despite limited exposure to daylight in the restrictedanimals, but phasor angles were not, suggesting a significant change in circadian phase angle with differentabsolute light exposure levels.

ConclusionThe Daysimeter-D offers new opportunities for research into the behavior, proximal light exposure patterns, and

circadian entrainment of lemurs and for deeper insight into the promotion of health and well-being of these endangeredstrepsirrhine primates.

ReferencesFigueiro MG, Hamner R, Bierman A, Rea MS. 2013. Comparisons of three practical field devices used to measure personal light

exposures and activity levels. Lighting Research and Technology, 45(4):421-434.Miller D, Bierman A, Figueiro MG, Schernhammer ES, Rea MS. 2010. Ecological measurements of light exposure, activity and circadian

disruption. Lighting Research & Technology, 42(3):271-284.Mittermeier RA, Louis Jr. EE, Richardson M, et al. 2010. Lemurs of Madagascar, 3rd Ed. Conservation International, Bogotá, Colombia.Rea MS, Bierman A, Figueiro MG, Bullough J. 2008. A new approach to understanding the impact of circadian disruption on human

health. Journal of Circadian Rhythms, 6:7.Rea MS, Figueiro MG, Jones GE, Glander KE. 2014. Daily activity and light exposure levels for five species of lemurs at the Duke Lemur

Center. American Journal of Physical Anthropology, 153(1):68-77.

Figure 1

Figure 2a Figure 3a Figure 4a Figure 5a Figure 6a

Figure 6b

Figure 2 Figure 3 Figure 4 Figure 5 Figure 6