Karels, Tim J - California State University, Northridge

研究领域

My research interests are in understanding the diversity of processes that influence population growth in natural populations. This is a central and long-standing problem in ecology with fundamental importance in understanding population dynamics and the conservation of species. I use ground-dwelling squirrels (ground squirrels and marmots) as a model system for exploring ecological, behavioral, physiological, and evolutionary mechanisms that determine population growth. They are a taxonomically diverse group of rodents with different mating systems, social structure, and population dynamics distributed throughout the northern hemisphere from arid tropics to arctic and alpine environments. Consequently they are an excellent group with which to comparatively and/or experimentally test hypotheses in population regulation and life-history theory.

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Nolan, P., F. S. Dobson, T. J. Karels, K. J. McGraw, P. Jouventin. 2010. Mutual mate choice for colorful traits in king penguins. Ethology. 117: 635-644 Karels. T. J., F. S. Dobson, H. S. Zimbler-DeLorenzo, and A. L. Skibiel. 2009. Testing causal structure in the biogeography of avian extinctions on oceanic islands. Journal of Biogeography. 36: 1613-1622. Trevino, H. S., A. L. Skibiel, T. J. Karels, and F. S. Dobson. 2008. Why causal analysis of threats to oceanic avifaunas is important: reply to Blackburn et al. Conservation Biology. 22: 495-497 Karels, T. J., F. S. Dobson, H. S. Trevino, and A.L. Skibiel. 2008.The biogeography of avian extinctions on oceanic islands. Journal of Biogeography. 36:1106-1111. Kyle, C. J., T. J. Karels, C. S. Davis, S. Mebs, B. Clark, C. Strobeck, D. S. Hik. Social structure and facultative mating systems of hoary marmots (Marmota caligata). Molecular Ecology. 16: 1245-1255. [pdf] Trevino, H. S., A. L. Skibiel, T. J. Karels, F. S. Dobson. 2007. Threats to avifauna on oceanic islands. Conservation Biology. 21: 125-132. [pdf] Gillis E. A., D. S. Hik, R. Boonstra R., T. J. Karels, and C. J. Krebs. 2005. Being high is better: effects of elevation and habitat on arctic ground squirrel demography. Oikos. 108:231-240. [pdf] Karels, T. J, L. Koppel., and D. S. Hik. 2004. Fecal pellet counts as a technique for monitoring an alpine dwelling social rodent, the hoary marmot (Marmota caligata). Arctic, Antarctic, and Alpine Research. 36:490-494. [pdf] Kyle, C.J., T. J. Karels, B. Clark, C. Strobeck, D.S. Hik, and C.S. Davis. 2004. Isolation and characterization of microsatellite markers in hoary marmots (Marmota caligata). Molecular Ecology Notes. 4: 749-751. [pdf] Karels, T. J., A. B. Bryant, and D. S. Hik. 2004. Comparison of discriminant function and classification tree analyses for age classification of marmots. Oikos. 105:575-587. [pdf] Karels, T. J. 2004. Squirrels and Relatives II: Ground Squirrels. In Grzimek's Animal Life Encyclopedia: Mammals. 2nd Edition. Volume 16. Gale, Detroit. Karels, T. J. and R. Boonstra. 2003. Reducing solar heat gain during winter: the role of white bark in northern deciduous trees. Arctic. 58:168-174. [pdf] [cover] Karels, T. J., J. Brashares, and A. Bryant. 2003. Borrowing from burrowers: conservation lessons from alpine dwelling marmots. In Mountain Science Highlights. The State of Ecological and Earth Sciences in Mountain Areas. Proceedings of the Conferences on Ecological and Earth Sciences in Mountain Areas. September 6-10, 2002, Banff, Alberta. Available online at http://www.forestry.ubc.ca/alpine/highlights Boonstra, R., C. J. McColl, and T. Karels. 2001. Reproduction at all costs: how breeding compromises the stress response and survival in male arctic ground squirrels. Ecology. 82:1930-1946. [pdf] Boonstra, R., S. Boutin, A. Byrom, T. Karels, A. H. Hubbs, K. Stuart-Smith, and M. Blower. 2001. The role of red squirrels and arctic ground squirrels. Chapter 9. In C. J. Krebs, S. Boutin, and R. Boonstra, editors. Ecosystem Dynamics of the Boreal Forest: The Kluane Project. Oxford University Press. ISBN: 0-19-513393-5 Karels, T. J. and R. Boonstra. 2000. Concurrent density dependence and independence in arctic ground squirrels. Nature. 408: 460-463. [pdf] Byrom, A. E., T. Karels, C. J. Krebs, and R. Boonstra. 2000. Experimental manipulation of predation and food for arctic ground squirrels in the boreal forest. Canadian Journal of Zoology. 78:1309-1319. [pdf] Karels, T. J., A. Byrom, R. Boonstra, and C. J. Krebs. 2000. The interactive effects of food and predators on reproduction and overwinter survival of arctic ground squirrels. Journal of Animal Ecology. 69:235-247. [pdf] [cover] Hubbs, A., T. Karels, and R. Boonstra. 2000. Indices of population size for burrowing mammals. Journal of Wildlife Management. 64:296-301. Karels, T. J. and R. Boonstra. 1999. The impact of predation on burrow use by arctic ground squirrels in the boreal forest. Proceedings of the Royal Society of London. Series B. 266:2117-2123. [pdf] Ben-David, M., C. J. McColl, R. Boonstra, and T. J. Karels. 1999. 15N signatures do not reflect body condition in Arctic ground squirrels. Canadian Journal of Zoology. 77:1373-1378. [pdf] Hubbs, A., Karels, T., and Byrom, A. 1996. Tree-climbing as a possible antipredator behaviour in Arctic ground squirrels, Spermophilus parryii. Canadian Field Naturalist. 110:533-534. [pdf] Boutin, S., C. J. Krebs, R. Boonstra, M. R. T. Dale, S. J. Hannon, K. Martin, A. R. E. Sinclair, J. N. M. Smith, R. Turkington, M. Blower, A. Byrom, F. I. Doyle, C. Doyle, D. Hik, L. Hofer, A. Hubbs, T. Karels, D. L. Murray, V. Nams, M. O'Donoghue, C. Rohner, and S. Schweiger. 1995. Population changes of the vertebrate community during a snowshoe hare cycle in Canada's boreal forest. Oikos. 74:69-80. [pdf]