Survival, Home Range, and Colony Reproduction of Beavers in East-Central Illinois, an Agricultural Landscape

Abstract

We estimated survival, examined habitat factors that affect home range size, and estimated colony reproduction for beavers (Castor canadensis) radio-tagged in east-central Illinois, an intensively farmed region. We monitored 42 radio-tagged beavers occupying the Embarras River and its tributaries from Sept. 2004 through Aug. 2006. Trapper harvest and disease contributed equally to low survival in 2004–2005 (0.29 ± 0.08), but had a lower impact in 2005–2006, resulting in higher survival (0.59 ± 0.13). Linear home ranges were longer for beavers in the river (50% = 1.2 km; 95% = 3.6 km) than for those in streams (50% = 0.7 km; 95% = 1.8 km). Distance of the den to crop fields, stem density of least preferred woody species, and water fluctuations around dens were positively correlated with home range size. Two colonies on the main river produced 59% of the kits observed from 13 colonies. Food does not appear limited in the region; however, the distribution of food resources and extreme fluctuations in stream flow likely influence beaver movements and colony dynamics.