Impact of Recreational Snow Compactionon Small Mammals in the Subnivean Space

Derek Sweeney EBIO 4120 Spring 2008Mountain Research Station University of Colorado, Boulder

Questions:• Does recreational use of snow impact subnivean space characteristics?

• If so, what changes occur and what are the factors that control those changes?

• How do changes to the subnivean space impact small mammals that utilize that space?

Deer mousePeromyscus maniculatus

Home range:.02 - .3 hectares

Montane voleMicrotus montanus

Home range:.1 hectares

Small mammals that utilize the subnivean space

S. red-backed voleMyodes gapperi

Home range:.5 hectares .14 hectares in winter

Masked shrewSorus cinereus

Home range:.5 - .6 hectares

Small mammals that utilize the subnivean space

HOME RANGES

• Most home range research for summer

• Very little research on effect of snow cover on home range and activity of small mammals (Sanecki, et al., 2006)

• Snowpack causes significant reduction in home ranges (Sanecki, et al., 2006)

•Snow limits access to food sources (Korslund, 2006)

•Snow affects ability to forage enough food

Predators that rely on subnivean animals

Ermine

BobcatCoyote

Subnivean Space in Continental Snowpack

Small mammal use of subnivean space

•Small mammals depend on the development of the subnivean space between ground and snow to enable access to resources necessary for survival (Formozov 1946; Pruitt 1984; Halfpenny and Ozanne 1989)

• Protection from predators

• Insulation from low surface temperatures

• Constant temperature maintenance (0o C)

• Ease of travel in low density, unconsolidated snow

Subnivean space due to depth hoar (average 16 cm)

Evidence of small mammal tunneling in subnivean space

Snow Compaction Due to Single Pass on Skis

• Type of load force/area, ski, snowshoe, snowmobile

• Frequency of load number of times an area is compacted

• Snow depth how deep can compaction effect penetrate

Possible factors affecting changes in the subnivean space

SITE• Lodgepole pine forest• Typical area of recreational use•Open, uniform, undisturbed site•Snow without melt/freeze crusts

• Compressed snow with skis• Measured change in height of subnivean space and snow density • First experiment: varied snow depth, held load and frequency constant

•Second experiment: varied frequency, held load and snow depth (65 cm) constant

METHODS

Ski compaction of snowpack

Reduction of subnivean space height due to ski compaction in different depths of snow

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Increase in snow density in the subnivean space due to ski compaction in different depths of snow

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Reduction in height of subnivean space in response to increasing frequency of use

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RESULTS SUMMARY• There are effects on the subnivean space

• Factors influencing subnivean change include snow depth, frequency of use, and type of load

• Height of the subnivean space and snow density affected

•With snowpack greater than 100 cm, compaction effects don’t extend to the subnivean space

•Compaction effect stabilizes after 3-5 passes

DISCUSSION

Potential effects on small mammals(Sanecki et al. 2006)• Loss of space• Increased energy to travel• Forced to surface• Reduce/fragment home ranges/habitat• reduced insulation/thermal stability• Barriers to travel and access to food

•compaction may benefit some other mammals in the short term reduced transportation energy use for deer, elk, moose trails to increase coyote hunting range but also unexpected effects, lynx decline due to opening of range to coyotes

APPLICATION TO MANAGEMENT/PLANNING OF SNOW COVERED RECREATIONAL AREAS

• Be aware of the importance of the subnivean space

• Need more winter mammal surveys, home ranges

• Restrict early season travel on shallow snowpack

• Limit travel to designated trails in high use areas

• Make travel corridors narrower with more tree islands

•Suggestions to provide tunnels

REFERENCES

• Belk MC, Smith HD, Lawson. 1988. Use and partitioning of montane habitat by small mammals. Journal of Mammalogy. 69:4, pp. 688-695.

• Formozov AN. 1946. Snow cover as an integral factor of theenvironment and its importance in the ecology of mammals and birds.Boreal Institute: Edmonton.

• Hadley GL, Wilson KR. 2004. Patterns of small mammal density andsurvival following ski-run development. Journal of Mammalogy.85:1, pp. 97-104.

• Halfpenny JC and Ozanne RD. 1989. Winter: an Ecological Handbook.Johnson Publishing Company: Boulder, CO.

• Korslund L, Steen H. 2006. Small rodent winter survival: snow conditions limit access to food resources. Journal of Animal Ecology. 75:1, pp. 156-166.

REFERENCES• Musser, G. G. and M. D. Carleton. 2005. Superfamily Muroidea. Pp. 894-1531 in Mammal Species of the World a Taxonomic and Geographic Reference. D. E. Wilson and D. M. Reeder eds. Johns Hopkins University Press, Baltimore.

•Pruitt, WO Jr. 1984. Snow and small animals. In Winter Ecology ofSmall Mammals. Special publication No. 10. (Ed. J.F. Merritt) pp. 1-8.Carnegie Museum of Natural History: Pittsburgh, PA.

•Sanecki GM, Cowling A, Green K, et al. 2006. Winter distribution of small mammals in relation to snow cover in the subalpine zone. Journal of Zoology. 269:1, pp. 99-110.

•Sanecki GM, Green K, Wood H, et al. 2006. The implications of snow-based recreation for small mammals in the sub-nivean space. Biological Conservation. 129:4, pp. 511-518.

•Sanecki GM, Green K, Wood H, et al. 2006. The influence of snow coveron home range and activity of the bush-rat (rattus fuscipes) and thedusky antechinus (Antechinus swainsonii). Wildlife Research. 33:6, pp. 489-496.

Deer mouse

Masked shrew Southern red-backed vole

Montane vole

Small Mammals Utilizing the Subnivean Space