Why do female Belding's ground squirrels disperse away from food resources? |
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Authors: | Scott Nunes Peter A Zugger Anne L Engh Kurt O Reinhart Kay E Holekamp |
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Institution: | (1) Department of Zoology, Michigan State University, East Lansing, MI 48824-1115, USA Tel: (517) 353-3771; Fax: (517) 432-2781; e-mail: nunessco@pilot.msu.edu, US;(2) Department of Biology, Appalachian State University, Boone, NC 28608, USA, US |
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Abstract: | We examined the effects of food provisioning on the natal dispersal behavior of Belding's ground squirrels (Spermophilus beldingi). We provided extra food to adult and yearling females in their maternal territories during pregnancy and lactation, and
to offspring of these females in their natal areas for 6 weeks after weaning. We used unprovisioned young of unprovisioned
mothers as controls. Provisioning influenced the probability of dispersal from the natal area by female but not male S. beldingi. All surviving male S.␣beldingi dispersed by 55 weeks of age, regardless of whether they and their mothers received extra food. By contrast, we observed
a significant trend, beginning 3 weeks after weaning and continuing through the yearling year, for a greater proportion of
provisioned than control female S. beldingi to emigrate from the natal area. Competition for food did not appear to influence natal dispersal of females. However, overall
population density, density of females weaning litters, and rates of aggression and vigilance among these females, were higher
in provisioned than control areas, suggesting that competition for non-food resources was unusually intense in provisioned
areas. We propose that juvenile female, but not juvenile male, S. beldingi may emigrate from the natal site to increase access to areas with low densities of conspecifics. Together with findings of
earlier workers, our results suggest that spatial and temporal distributions of environmental resources are important influences
on the dispersal behavior of female ground squirrels.
Received: 28 February 1996 / Accepted after revision: 16 October 1996 |
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Keywords: | Natal dispersal Competition Sex differences Ground squirrel |
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