Dispersal pattern and effective population size of the beaver

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Biological Sciences

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The dispersal pattern of the beaver (Castor canadensis) was studied by intensive livetrapping, tagging, and observation in Allegany State Park and its vicinity in New York from 1984 to 1996. The majority (74%) of dispersing beavers (n = 46) initiated dispersal in a downstream direction after spring ice-out. Females dispersed significantly farther away from their natal colonies than males (10.15 ± 2.42 (SE) km vs. 3.49 ± 0.86 km). Movements to neighboring sites were common (16 of 46 dispersers), indicating that beavers, especially males, may prefer to disperse to the nearest available sites. Most (64%) natal dispersers were 2-year-olds. Three-year-olds also constituted a considerable proportion (21%) of the dispersers, but 1-year-old dispersers were relatively rare (14%). Many adults underwent secondary dispersal after successful natal dispersal in our study area. Male secondary dispersers were more inclined to take over neighboring sites than were male natal dispersers (10 of 13 vs. 3 of 13). The effective population size in a 250-km2 area was estimated to be 161-228 individuals by the areal method and 267-378 individuals by the 85th percentile method.


This article was originally published in Canadian Journal of Zoology. The full-text article from the publisher can be found here.

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Canadian Journal of Zoology


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