A Comparison of Abert squirrels, pine squirrels and fox squirrels
1 / 22

A Comparison of Abert squirrels - PowerPoint PPT Presentation

  • Updated On :

A Comparison of Abert squirrels, pine squirrels and fox squirrels with respect to life in the cold by Justina Thorsen 2006. Winter Ecology – Spring 2006 Mountain Research Station – University of Colorado, Boulder. Topic under Consideration.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'A Comparison of Abert squirrels' - Jeffrey

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Slide1 l.jpg

A Comparison of Abert squirrels, pine squirrels and fox squirrelswith respect to life in the coldby Justina Thorsen2006

Winter Ecology – Spring 2006

Mountain Research Station – University of Colorado, Boulder

Topic under consideration l.jpg
Topic under Consideration squirrels

  • Abert, fox and pine squirrels have overlapping ranges in Boulder Mountain Parks (BMP). What are their different adaptations to the cold winters on the Colorado Front Range?

The tree squirrels l.jpg
The Tree Squirrels squirrels

  • Sciurus = derived from Greek terms “shadow” and “tail”

    • Thus, an animal who sits in the shadow of it’s tail (Gurnell 1987; MacClintock 1970)

  • Tamias = food caching

  • Bushy tails for: balance, communication and Tbody regulation

    • Tails often approach 1/3 of body length

  • Hindfeet with 5 digits, forefeet with 4 digits

    • May be furry in winter (Gurnell 1987)

  • Three species considered l.jpg
    Three Species Considered squirrels

    Tamiasciurus hudsonicus

    Sciurus aberti

    Sciurus niger

    Where are they l.jpg
    Where Are They? squirrels

    Distribution of the Abert squirrel

    Where are they6 l.jpg
    Where are They? squirrels

    Distribution of the Fox Squirrel

    Where are they7 l.jpg
    Where are They? squirrels

    Distribution of the pine squirrel

    Nest types l.jpg
    Nest Types squirrels

    • Dreys: twig and leaf nests built in trees

      • Winter dreys are more elaborate than summer ones & must withstand inclement weather

      • Winter dreys tend to be circular; summer dreys saucer shaped

  • Dens: holes or cavities in tree trunks

  • Holes: underground or in rock

    (Gurnell 1987)

  • Body size and bergman s rule l.jpg
    Body Size and Bergman’s Rule squirrels

    • In order of increasing size: pine, abert, fox

      • Pine squirrels are smallest N. American tree squirrel

        • Occupy the coldest, most northern habitats in N. America and the highest altitudes in Colorado

      • Fox squirrels are largest N. American tree squirrel

        • Occupy the lowest altitudes in Colorado

    Coat color l.jpg
    Coat Color squirrels

    • Abert squirrels of Colorado tend to be melanistic

      • Farentinos (1971) estimated 56.7% melanism

  • Pine squirrels are ashy gray with white undersides

  • Fox squirrels are peanut colored with rusty undersides

  • Is black beneficial l.jpg
    Is Black Beneficial? squirrels

    • Golightly and Ohmart (1978) found that:

      • Sun basking is common among Abert squirrels on winter afternoons

      • Sun basking resulted in increased TBody

      • Basking squirrels had higher TBody than inactive and nesting squirrels

    Food utilization l.jpg
    Food Utilization squirrels

    • Fox and pine squirrels are food generalists and opportunistic eaters

    • Abert’s are food specialists and are ecologically dependent upon Ponderosa pines

    • The primary food for all squirrels is tree seeds and fruits

    • Secondary foods: berries, mushrooms and other plant matter

    Selective herbivory of abert squirrels l.jpg
    Selective herbivory of Abert squirrels squirrels

    • Diet consists almost entirely of ponderosa pine tissues and other closely associated species (Snyder 1998, States and Wettstein 1998)

    • Abert squirrels eat mycorrhizal fungi in the summer months and inner bark during winter months (States and Wettstein 1998)

    Food caching of pine squirrels l.jpg
    Food Caching of Pine Squirrels squirrels

    • Pine squirrels establish middens which they guard defensively

    • They cut and cache green cones in late summer to ripen and provide winter food sources (MacClintock 1970)

    • Middens often have underground networks of tunnels and nest cavities

    Fall gluttony of fox squirrels l.jpg
    Fall Gluttony of Fox Squirrels squirrels

    • Fox squirrels prepare for the unpredictability and scarcity of food resources during winter by overeating in the fall (Steel and Koprowski 2001)

    • Fox squirrels may scatterhoard food

    Levels and patterns of activity l.jpg
    Levels and Patterns of Activity squirrels

    • Inclement weather reduces activity, although active squirrels may be seen in severe weather

      • Wind and rain significantly reduce Tbody (Golightly and Ohmart 1978)

      • Fresh snow severely restricts movements (Golightly and Ohmart 1978)

      • Pine squirrels become subnivean and subterranean when Tair is very low (Gurnell 1987)

    Summary of adaptations l.jpg
    Summary of Adaptations squirrels

    • Aberts:

      • Behavioral – sun basking

      • Morphological – ear tufts, black coat

      • Physiological – utilization of inner bark

  • Pine Squirrels:

    • Behavioral – middens, territorial

  • Fox Squirrels:

    • Behavioral – fall gluttony, scatterhoarding

    • Morphological/Physiological - BAT

  • Conclusions l.jpg
    Conclusions squirrels

    • The three species of tree squirrels each exhibit unique sets of adaptations to life in the cold.

    • All three species experience similar environmental pressures where their ranges overlap (on the Front Range of BMP)

    • All three species exhibit a degree of inhibition from inclement weather (including: wind, rain, fresh snow, low Tair)

    Selected references and literature cited l.jpg
    Selected References and Literature Cited squirrels

    Armstrong, D.M. 1987. Rocky Mountain Mammals, revised edition. Boulder,

    Colorado: Colorado Associated University Press. 223 pp

    Farentinos, R.C. 1971. Social dominance and mating activity in the tassel-eared squirrel

    (Sciurus aberti ferrus). Unpublished. PhD Thesis for the University of Colorado, Boulder. 73 pp.

    Golightly, RT Jr. and RD Ohmart. 1978. Heterothermy in free ranging Abert’s squirrels (Sciurus aberti). Ecology, 59(5): 897-909.

    Gurnell, J. 1987. The Natural History of Squirrels. New York, New York: Facts on File

    Publications. 201 pp.

    Hamilton, WJ III and F Heppner. 1967. Radiant solar energy and the function of black homeotherm pigmentation: an hypothesis. Science, 155: 196-197.

    Slide21 l.jpg

    Keith, JO. 1965. The Abert squirrel and its dependence on Ponderosa pine. Ecology, 46: 150-163.

    MacClintock, D. 1970. Squirrels of North America. New York, New York: Van Nostrand Reinhold Company. 184 pp.

    Larson, MM and GH Schubert. 1970. Cone crops of ponderosa pine in central Arizona including the influence of Abert squirrels. USDA Forest Service Research Paper RM-58, Rocky Mtn. Forest and Range Experiment Station, Ft. Collins Colorado. Pp. 15.

    Marchand, PJ. 1987. Life in the Cold. Hanover: University Press of New England. 304 pp.

    Snyder, M.A. 1998. Abert’s squirrels (Sciurus aberti) in Ponderosa pine (Pinus

    ponderosa) forests: directional selection, diversifying selection. In: Steel J.F. and D.A. Zegers (eds). Ecology and Evolutionary Biology of Tree Squirrels. 6th Special Publication. VA: Virginia Museum of Natural History. p 195-201.

    States J.S. and P.J. Wettstein. 1998. Food habits and evolutionary relationships of the tassel-eared squirrel (Sciurus aberti). In: Steel J.F. and D.A. Zegers (eds). Ecology and Evolutionary Biology of Tree Squirrels. 6th Special Publication. VA: Virginia Museum of Natural History. p 185-194.

    Slide22 l.jpg

    Steel, MA and JL Koprowski. 2001. North American Tree Squirrels. Washington: Smithsonian Institute Press. 201pp.