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The demographic response of bank-dwelling beavers to flow regulation: A comparison on the Green and Yampa rivers

Canadian Journal of Zoology
By: , , and 
https://doi.org/10.1139/z01-162

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Abstract

We assessed the effects of flow regulation on the demography of beavers (Castor canadensis) by comparing the density, home-range size, and body size of bank-dwelling beavers on two sixth-order alluvial river systems, the flow-regulated Green River and the free-flowing Yampa River, from 1997 to 2000. Flow regulation on the Green River has altered fluvial geomorphic processes, influencing the availability of willow and cottonwood, which, in turn, has influenced the demography of beavers. Beaver density was higher on the Green River (0.5–0.6 colonies per kilometre of river) than on the Yampa River (0.35 colonies per kilometre of river). Adult and subadult beavers on the Green River were in better condition, as indicated by larger body mass and tail size. There was no detectable difference in home-range size, though there were areas on the Yampa River that no beavers used. We attribute the improved habitat quality on the Green River to a greater availability of willow. We suggest that the sandy flats and sandbars that form during base flows and the ice cover that forms over winter on the Yampa River increase the energy expended by the beavers to obtain food and increase predation risk and thus lowers the availability of woody forage.

Publication type Article
Publication Subtype Journal Article
Title The demographic response of bank-dwelling beavers to flow regulation: A comparison on the Green and Yampa rivers
Series title Canadian Journal of Zoology
DOI 10.1139/z01-162
Volume 79
Issue 11
Year Published 2001
Language English
Publisher NRC Research Press
Contributing office(s) Fort Collins Science Center
Description 8 p.
First page 1957
Last page 1964
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