WINTERTIME MAMMAL ACTIVITY – SPECIFIC ENVIRONMENTAL CONTROLS

Brian Inglis

EBIO 4100-570 - Winter EcologyMountain 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 AnswersAll together now!….

Snow

Cold

Radiation

Energy

Wind

Predation

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, 151-300cm, 301-450cm, 451cm +)

Ranked snow depths similarly into 5 categories (Bare, 1-30cm, 31-60cm, 61-90cm, 91-120cm)

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…. H01: The

differences in the number of tracks from one site to another is due to random chance

H1: The differences in the number of tracks from one site to another is due to distance from vegetation

ANOVA Results: Df Sum of Squares Mean of Squares F value P Value

Distance Class 1 1251.3 1251.3 74.48 0.0001Reject null H 01

Aspect 2 15.5 7.8 0.461 0.6510Can’t reject null H 02

DistanceClass:Aspect 2 4.4 2.2 0.132 0.8788Can’t reject null H 03residuals 6 100.8 16.8

….two-factor analysis of variance without replacement…. H02: The

differences in the number of tracks from one site to another is due to random chance

H2: The differences in the number of tracks from one site to another is due to slope aspect

ANOVA Results: Df Sum of Squares Mean of Squares F value P Value

Distance Class 1 1251.3 1251.3 74.48 0.0001Reject null H 01

Aspect 2 15.5 7.8 0.461 0.6510Can’t reject null H 02

DistanceClass:Aspect 2 4.4 2.2 0.132 0.8788Can’t reject null H 03residuals 6 100.8 16.8

….two-factor analysis of variance without replacement…. H03: any

interaction between aspect and vegetation density is due to random chance

H3: aspect has some control over the density of vegetation present

ANOVA Results: Df Sum of Squares Mean of Squares F value P Value

Distance Class 1 1251.3 1251.3 74.48 0.0001Reject null H 01

Aspect 2 15.5 7.8 0.461 0.6510Can’t reject null H 02

DistanceClass:Aspect 2 4.4 2.2 0.132 0.8788Can’t reject null H 03residuals 6 100.8 16.8

Conclusions

Analysis of variance Strong positive

correlation between vegetation density and mammal tracks P-value of 0.0001

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 360⁰Vegetation density biasedSite 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: 10.1111/j.1472-4642.2010.00638.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: 437-449. doi: 10.1016/j.biocon.2007.03.001

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