Conservation on the Edge

Dr. John Koprowski in the School of Natural Resources and the Environment takes a special interest in what happens to populations at the edges of their range. Range edges are constantly growing due to fragmentation - and these are the places where we are likely to see striking ecological shifts as the climate changes.

Here in Southern Arizona, new populations and new species are created among the Sky Islands - a series of forested mountaintops, divided by desert and grassland valleys, that stretches into northern Mexico. These forests have been discontinuous for about seven to ten thousand years - which has led to the differentiation of a subspecies of red squirrel, the federally endangered Mount Graham Red Squirrel.

Koprowski, his colleagues and students have intensively tracked this population for 8 years - identifying threats to the squirrel from forest insect dynamics to competition from introduced Abert's squirrels. Although conservation measures are already in place, concerns about the animal's viability have increased as numbers have more than halved since 1999, dropping from 562 to a recent low of 199. Dr. Koprowski notes that if we can't save a species in a relatively controlled, isolated environment like Mt Graham, it doesn't bode well for effective conservation of other species in more complex situations.

Progress to date:

The efforts of Dr. Koprowski and members of his research group have provided important insight into the challenges facing the endangered red squirrel and its conservation. Insect damage to trees and fire remain threats to this forest-dwelling species. Individuals range widely on Mt. Graham and appear to experience high mortality rates and small litter sizes. Introduced Abert's squirrel may pose a major threat as predicted by population modeling by the Koprowski research group and suggested by their field data. Furthermore, cones in Mt. Graham red squirrel food stores are sensitive to relatively small changes in temperature and moisture. Warm and dry conditions lead to the opening of cones and the loss of seeds once sequestered under each cone scale. Predicted changes in climate will make some middens less suitable and provide a long-term challenge to the conservation of the species. These findings have been well received by the major state and federal agencies and are currently being incorporated into forest and population management plans. Further details can be found in the sampling of publications produced by Dr. Koprowski's group and listed below.

Key Collaborators:

Steve Rushton and Peter Lurz, Centre for Life Sciences Modeling, University of Newcastle upon Tyne

Richard W. Thorington, Smithsonian Institution

Michael Steele, Wilkes University

Sam Drake, Office of Arid Lands, University of Arizona

Melanie Culver, USGS Arizona Cooperative Fish and Wildlife Research Unit

Ann Lynch, USDA Forest Service, Rocky Mountain Research Station

William Van Pelt, Arizona Game & Fish Dept, Nongame Bird and Mammal Program Manager

References:

Sanderson, H.R., and J. L. Koprowski. The Mt. Graham Red Squirrel and Its Last Refuge, University of Arizona Press (In press).

Edelman, A. J. and J. L. Koprowski. 2007. Communal nesting in asocial Abert's squirrels: the role of social thermoregulation and breeding strategy. Ethology 113: 147-154.

Edelman, A. J. and J. L. Koprowski. 2006. Seasonal changes in home ranges of Abert's squirrels: Impact of mating season. Canadian Journal of Zoology 84: 404-411.

Edelman, A. J. and J. L. Koprowski. 2006. Characteristics of Abert's squirrel (Sciurus aberti) cavity nests. The Southwestern Naturalist 51(1): 64-70.

Edelman, A. J. and J. L. Koprowski. 2005. Selection of drey sites by Abert's squirrels in an introduced population. Journal of Mammalogy 86(6): 1220-1226.

Edelman, A. J., J. L. Koprowski, and J. L. Edelman. 2005. Kleptoparasitic behavior and species richness at Mt. Graham red squirrel middens. USDA Forest Service Proceedings RMRS-P-36: 395 - 398.

Edelman, A. J. and J. L. Koprowski. 2005. Diet and tree use of Abert's squirrels (Sciurus aberti) in a mixed-conifer forest. The Southwestern Naturalist 50(4): 461-465.

Hutton, K. A., J. L. Koprowski, V. L. Greer, M. I. Alanen, C. A. Schauffert and P. J. Young. 2002. Use of Spruce-Fir and Mixed-Conifer Forests by an Introduced Population of Abert's Squirrels (Sciurus aberti). The Southwestern Naturalist 48: 257-260.

Koprowski, J. L., S. R. B. King, and M. J. Merrick. 2007. Expanded home ranges in a peripheral population: space use by endangered Mt. Graham red squirrels. Endangered Species Research 3: 1-6.

Koprowski, J. L., N. Ramos, B. S. Pasch, and C. A. Zugmeyer. 2006. Observations on the ecology of the endemic Mearns's squirrel (Tamiasciurus mearnsi). The Southwestern Naturalist 51(3): 426-430.

Koprowski, J. L., K. M. Leonard, C. A. Zugmeyer, and J. L. Jolley. 2006. Direct effects of fire on endangered Mount Graham red squirrels. The Southwestern Naturalist 51(1): 59-63.

Koprowski, J. L., M. I. Alanen, and A. M. Lynch. 2005. Nowhere to run and nowhere to hide: Response of endemic Mt. Graham red squirels to catastrophic forest damage. Biological Conservation 126: 491-498.

Koprowski, J. L. 2005. Annual cycles in body mass and reproduction of endangered Mt. Graham red squirrels. Journal of Mammalogy 86(2): 309-313.

Koprowski, J. L. 2005. Management and conservation of tree squirrels: The importance of endemism, species richness, and forest condition. USDA Forest Service Proceedings RMRS-P-36: 245-250.

Koprowski, J. L., A. J. Edelman, B. S. Pasch, and D. C. Buecher. 2005. A dearth of data on the mammals of the Madrean archipelago: What we think we know and what we actually know. USDA Forest Service proceedings RMRS-P-36: 412- 415.

Koprowski, J. L. 2005. The response of tree squirrels to fragmentation: A review and synthesis. Animal Conservation 8: 369-376. PDF of Article

Koprowski, J. L. 2002. Handling tree squirrels with a safe and efficient restraint. Wildlife Society Bulletin 30: 101-103.

Merrick, M. J., S. R. Bertelsen, and J. L. Koprowski. 2007. Characteristics of Mount Graham red squirrel nest sites in a mixed conifer forest. The Journal of Wildlife Management 71(6): 1958-1963.

Rushton, S. P., D. J. A. Wood, P. W. W. Lurz, and J. L. Koprowski. 2006. Modelling the population dynamics of the Mt. Graham red squirrel: Can we predict its future in a changing environment with multiple threats? Biological Conservation 131: 121-131.

Schauffert, C. A., J. L. Koprowski, V. L. Greer, M. I. Alanen, K. A. Hutton, and P. J. Young. 2002. Interactions Between Predators and Mt. Graham Red Squirrels (Tamiasciurus hudsonicus grahamensis). The Southwestern Naturalist 47: 498-501.

Steele, M. A., and J. L. Koprowski. 2001. North American Tree Squirrels. Smithsonian Institution Press: Washington, DC. 224 p.

Wood, D. J. A., S. Drake, S. P. Rushton, D. Rautenkranz, P. W. Lurz, and J. L. Koprowski. 2007. Fine-scale analysis of Mount Graham red squirrel habitat following disturbance. The Journal of Wildlife Management 71(7): 2357-2364.

Wood, D. J. A., J. L. Koprowski, and P. W. W. Lurz. 2007. Tree squirrel introductions: A theoretical approach with population viability analysis. Journal of Mammalogy 88(5): 1271-1279.

Zugmeyer, C. A. and J. L. Koprowski. 2007. Avian nestling predation by endangered Mt. Graham red squirrel. The Southwestern Naturalist 52(1): 155-157.