TERRITORIALITY AND TIME BUDGETS IN BEAVERS DURING SEQUENTIAL SETTLEMENT

Beavers (Castor fiber) were sequentially released into a previously un occupied area. The settlement of the animals approximated an ideal des potic distribution: they successively settled in rich habitat and then in poor habitat, and then became floaters. This pattern is regarded a s evidence that territorial behavior limited density. The early arriva ls showed a seasonal difference in territory size (small in winter, la rge in late spring and summer), which was expected from optimal territ ory size theory but which was not found in later arrivals. In the firs t 2 years, the beavers were swimming very large distances (up to 20.0 km per night), and were apparently undergoing a long-term decline in b ody condition. Body temperature decreased during swimming, especially in winter (daily amplitude 2.04 degrees C). Each year, winter territor ies were about the size (7.9 +/- 0.9 (SE) km, including 3.0 +/- 0.4 km of wooded banks) that beavers could patrol daily without losing body condition. The number of territories established at any one time durin g the 5 years of study was only half the carrying capacity calculated on the basis of the current length of wooded banks within territories, in accordance with the prediction for sequential settlement in linear habitats. However, extensive no-man's-land was not present between te rritories, but early arrivals claimed larger territories than later on es. Social and thermoregulatory factors seem to play an important role in determining the costs of territory defense, and hence territory si ze. Overexploitation of the beaver's main food source, willow (Salix s pp.), seems unlikely in this productive habitat.