Tim J. Karels

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We tested the hypothesis that adult male arctic ground squirrels (Spermophilus parryii plesius) exhibit an adaptive stress response during the mating period that may compromise their survival, whereas males at other times (nonreproductive adult males and juvenile males) have a normal functional stress response. We assessed the physiological responsiveness(More)
We examined whether arctic ground squirrel (Spermophilus parryii plesius) populations in northern boreal forest in the Yukon Territory, Canada, were limited by food, predators, or a combination of both, during the decline and low phases of a snowshoe hare cycle. From 1990 to 1995, populations were monitored in large-scale (1 km2) experimental manipulations.(More)
* Department of Biology, The Citadel, Charleston, SC, USA Department of Biological Sciences, Auburn University, AL, USA Centre d’Ecologie Fonctionelle et Evolutive, Centre Nacional de la Recherche Scientifique, Montpellier, France § Animal Ecology Group, Centre for Ecological and Evolutionary Studies, University of Groningen, AA Haren, The Netherlands –(More)
No population increases without limit. The processes that prevent this can operate in either a density-dependent way (acting with increasing severity to increase mortality rates or decrease reproductive rates as density increases), a density-independent way, or in both ways simultaneously. However, ecologists disagree for two main reasons about the relative(More)
Microsatellite loci were developed from hoary marmots ( Marmota caligata ) to aid in the investigation of the social structure and mating system of this species. Seven of the microsatellite loci developed were found to be moderately polymorphic with between two and seven alleles per locus. In addition to the microsatellites developed in hoary marmots we(More)
For socially hibernating mammals, the effectiveness of huddling as a means of energy conservation should increase with group size. However, group size has only been linked to increased survival in a few hibernating species, and the relative importance of social structure versus winter conditions during hibernation remains uncertain. We studied the influence(More)
We investigated the effect of local environment on the demography and population dynamics of arctic ground squirrels (Spermophilus parryii plesius ) by comparing reproduction, survival, and population trends of squirrels living in low elevation boreal forest and high elevation alpine tundra sites in southwestern Yukon Territory, Canada. Contrary to the(More)
Mate-choice theory predicts different optimal mating systems depending on resource availability and habitat stability. Regions with limited resources are thought to promote monogamy. We tested predictions of monogamy in a social rodent, the hoary marmot (Marmota caligata), at the northern climatic extreme of its distribution. Mating systems, social(More)
In sedentary animals, the choice of a suitable home site is critical to survival and reproductive fitness. However, habitat suitability may vary with predation risk. We compared habitat use of Arctic ground squirrels (Spermophilus parryii plesius) living in the boreal forest under conditions of fluctuating predation pressure. In our study area, predators(More)
We evaluated fecal pellet counts as an index of hoary marmot (Marmota caligata) social group size in order to develop a simple, inexpensive method for monitoring population change of a widely distributed, but poorly studied alpine mammal. Fecal pellet counts were conducted in three separate seasons along several 2 m 3 100 m transects located parallel to and(More)