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Monogamy:

The beaver is monogamous because both the male and female are attached to their territory. This attachment is a result of the high amount of investment both sexes put into developing, maintaining, and defending their territory. If both parents survive, the union between the male and female is usually life long, but the male may breed with other females during his lifetime (Cahalane 1967, Caras 1967, Grzimek 1975). Mating occurs during the winter months of January and February when the beaver’s aquatic habitat is usually frozen over (Col 1998, NYSDC 2002, Shepherd 1994). In some locations, the mating season may continue into March (Grzimek 1975). Kits are born between April and June. The kits are able to swim and open their eyes immediately (Shepherd 1994). The average litter size is four, and the young spend most of their youth in the lodges where they are born, safe from predators (Jackson 1997). Kits are weaned at 3 months, but may stay with their parents to the age of two when they reach sexual maturity. (Shepherd, 1994)


	The Mating System and Social Relationships

	Photo courtesy of Oregon Museum of Science and Industry		Monogamy: The beaver is monogamous because both the male and female are attached to their territory. This attachment is a result of the high amount of investment both sexes put into developing, maintaining, and defending their territory. If both parents survive, the union between the male and female is usually life long, but the male may breed with other females during his lifetime (Cahalane 1967, Caras 1967, Grzimek 1975). Mating occurs during the winter months of January and February when the beaver’s aquatic habitat is usually frozen over (Col 1998, NYSDC 2002, Shepherd 1994). In some locations, the mating season may continue into March (Grzimek 1975). Kits are born between April and June. The kits are able to swim and open their eyes immediately (Shepherd 1994). The average litter size is four, and the young spend most of their youth in the lodges where they are born, safe from predators (Jackson 1997). Kits are weaned at 3 months, but may stay with their parents to the age of two when they reach sexual maturity. (Shepherd, 1994)
	The male and female beaver are co dominant within the colony because they are the only breeding pair on the territory. The breeding pair force their young to leave the colony before they reach sexual maturity at the age of two (Jackson 1997, Grzimek 1973, Shepherd 1994). Both the male and the female invest energy in caring for the young. Males and females also share the responsibility of construct dams, lodges, and bank dens, collecting food for the winter cache, and defending the territory by creating scent mounds and marking them with either the ASG secretions or castoreum (Lixing Sun 1988, 1997). Why Monogamy? The relationship between the male and female is obligate monogamy because the male is needed to ensure the female's reproductive success. Although both the male and female are involved in gathering food and territorial defense, the female could not take on the responsibilities of rearing offspring with out investment from the male. The male is needed to defend the pair’s valuable resources- the dam, and lodge and winter cache. The male is also needed to help gather food and timber for construction and habitat maintenance.
	Continue to the next page on Social Cooperation Link to Literature Cited Return to Beaver Home Page Return to Animal Behavior Home Page Return to Davidson College Biology Department Home Page This page was completed in partial fulfillment of the requirements for Biology 323, Animal Behavior, at Davidson College in the Spring Semester 2003.