Boreal beavers (Castor canadensis): Home range, territoriality, food habits and genetics of a mid-continent population.

摘要

studied beavers (Castor canadensis) in the boreal forest of eastern Manitoba from 1986 to 1992. I ear tagged 60 different beavers, and outfitted 42 of these with transmitters. I determined summer home range size for 34 beavers and fall home range size for 27 beavers. I examined: methods of delineating beaver home range; the effects of season, habitat, sex and age class on home range size; whether beavers were territorial; food selection by beavers; and genetic relatedness within the population.;I compared estimates of beaver home range size and shape using four different methods: grid; minimum convex polygon (MCP); modified minimum area (MMA); and the Jennrich-Turner ellipse. The grid method is most suitable for animals with irregularly shaped home ranges or home ranges with several areas of concentrated use, and appears best suited for use with beavers.;Summer home range areas average 10.34 ha and fall averaged 3.07 ha. Thirty-seven of 38 beavers had core areas in summer, and 21 of 27 had core areas in fall. Home range size and core size were positively correlated in both summer and fall. Summer home ranges were significantly larger than fall home ranges, with fall home ranges being centred closer to the lodge than summer ranges. Winter home ranges were restricted to less than 0.25 ha around the lodge.;Beavers living in river habitat had the largest summer and fall home ranges. Those living in pond habitats had the smallest summer home ranges but did not differ from lake beavers in the fall. Adult males usually had the largest home ranges, and adult females the smallest in both seasons. Adult females usually had home ranges centred closer to the lodge, and adult males farther from the lodge, than other family members.;I never observed any evidence of aggressive behaviour among beavers. Some overlap of home ranges occurred, especially on the river, but most home ranges were almost exclusive to a family group. I found no evidence that scent mounds delineated territory and no evidence to prove the presence of territories. I hypothesize that mutual avoidance is more likely than territorialism.;Beavers in the taiga show a preference for Populus tremuloides as a primary food in both spring and summer. In spring Pinus banksiana is also consumed. Beaver food choices appear to maximize protein intake and minimize potassium to sodium ratio.;DNA fingerprinting studies of 60 beavers showed a mean band sharing coefficient (BSC) among unrelated beavers of 0.36