WINTERTIME MAMMAL ACTIVITY – SPECIFIC ENVIRONMENTAL CONTROLS Brian Inglis EBIO Winter Ecology Mountain Research Station Spring ’12 CU Boulder Drawing courtesy of Marieta

Question… What are the dominant environmental factors controlling the distribution/abundance of overwintering mammals in the upper-montane and sub-alpine regions of Colorado?

Possible Answers All together now!….  S now  C old  R adiation  E nergy  W ind  P redation

Motivation  Food availability is an extremely influential variable in the wintertime --More so in the mountains?  Ecology 101  Vegetation as food chain supplier for all (Carnivores too)  How far will an organism go to get its food?  Depends on the obstacles  “snow cover alone does not fully explain the upper range limit of wombats… wombat occurrence is influenced by local habitat features (topography, soils, vegetation) in combination with maximum snow depth.” (Matthews et Al., 2010)  Diurnal radiation fluctuations and impact force from wind create ice crusts and packed layers suitable for travel  “…occupation was also positively associated with percent forest cover. …a reflection of the importance of proximal forest for weather and predator protection.”(Roger et Al., 2007)

What I Care About...  In what ways do aspect and vegetation density affect the presence of supranivean mammals in the winter? My Specific Hypotheses: H 1: Vegetation density affects the abundance of mammal tracks Denser stands more conducive to winter activity food availability and protection H 2: Aspect affects the abundance of mammal tracks Southern-facing hillsides more abundant in supranivean mammals benefits of radiation and wind.

Methodology 2 Sites 3 Aspects 4 Total Transects  Make a straight-line transect across terrain with constant aspect  At crossing track, noted species, snow depth and distance to nearest above-snow tree/vegetation  Ranked vegetation distances into four categories at 1.5m intervals (0-150cm, cm, cm, 451cm +)  Ranked snow depths similarly into 5 categories (Bare, 1-30cm, 31-60cm, 61-90cm, cm)  Analyze

Site Descriptions  Two transects of NORTH aspect  Average Altitude: 2877 m (9440’) A.S.L.  Vegetation:  Lodgepole and Limber Pine, Englemann Spruce, Aspen, Sub-Alpine Fir  Animals Found:  Mtn. Cottontail, Coyote, Tree Squirrel, Weasel  One SOUTHWEST facing transect, one SOUTHEAST facing  Average Altitude: 2621 m (8600’) A.S.L.  Vegetation:  Ponderosa and Lodgepole Pine, Englemann and Blue Spruce, Aspen  Animals Found:  Mtn. Cottontail, Coyote, Tree Squirrel, Moose Mountain Research Station Grounds - Fourmile Creek Tahosa Valley – Near Meeker Park, CO

Not Important:

….two-factor analysis of variance without replacement….  H 0 1 : The differences in the number of tracks from one site to another is due to random chance  H 1 : The differences in the number of tracks from one site to another is due to distance from vegetation ANOVA Results:DfSum of SquaresMean of SquaresF valueP Value Distance Class Reject null H 01 Aspect Can’t reject null H 02 DistanceClass:Aspect Can’t reject null H 03 residuals

….two-factor analysis of variance without replacement….  H 0 2 : The differences in the number of tracks from one site to another is due to random chance  H 2 : The differences in the number of tracks from one site to another is due to slope aspect ANOVA Results:DfSum of SquaresMean of SquaresF valueP Value Distance Class Reject null H 01 Aspect Can’t reject null H 02 DistanceClass:Aspect Can’t reject null H 03 residuals

….two-factor analysis of variance without replacement….  H 0 3 : any interaction between aspect and vegetation density is due to random chance  H 3 : aspect has some control over the density of vegetation present ANOVA Results:DfSum of SquaresMean of SquaresF valueP Value Distance Class Reject null H 01 Aspect Can’t reject null H 02 DistanceClass:Aspect Can’t reject null H 03 residuals

Conclusions  Analysis of variance  Strong positive correlation between vegetation density and mammal tracks P-value of  No discernible influence of aspect on mammal activity P-value of 0.65 Look at the longer-term bigger-picture  Hard to gauge the snow’s role  Support or Sink  Specific animal analysis  Subnivean controllers Not a complete 360 ⁰ Vegetation density biased Site differences

Final Thoughts…  Wintertime mammal activity not directly controlled by one factor  Aspect  SCREWP  Vegetation  P…. E…. W….  Vegetation density may/may not be dependent upon aspect  relation between two may be random, statistically Mammal abundance as a result not clear

References  Matthews, A., Spooner, P. G., Lunney, D., Green, K. and Klomp, N. I. (2010), The influences of snow cover, vegetation and topography on the upper range limit of common wombats (Vombatus ursinus) in the subalpine zone, Australia. Diversity and Distributions, 16: 277–287. doi: /j x  Roger, Erin, Shawn W. Laffin, and Daniel Ramp (2007), Habitat Selection by the Common Wombat (Vombatus Ursinus) in Disturbed Environments: Implications for the Conservation of a ‘common’ Species. Biological Conservation 137.3: doi: /j.biocon  Statistics run in R and Microsoft Excel  Topographic images courtesy of USGS 7.5’-minute series quadrangles “Ward”, “Allenspark” and “Longs Peak”  Expert Photography by Brian Inglis