NOTES ON AGE AT DISPERSAL OF BEAVER (CASTOR FIBER) IN AN EXPANDING POPULATION

Movements of nine young beavers (Castor fiber) that were trapped at th e front of an expanding population were monitored using radiotelemetry . Two years is generally considered the normal age at dispersal in bea vers, but in this study the ages at dispersal were evenly distributed between 11 and 23 months. At least one of the females in the study gav e birth at 2 years of age. Exploratory movements of three individuals outside the natal terrritory before the time of dispersal were observe d. The observed plasticity in age at dispersal and parturition indicat es that the rate of increase may be greater than expected at the front of expanding beaver populations.