Population dynamics of Newfoundland beaver

Abstract

The demography of beaver was studied in Newfoundland from 1956 to 1965. Population densities were low and seldom exceeded one colony per 2.6 km2 (1 mi2). About 80% of the adult females were fertile and the number of young per litter averaged 2.7. The annual mortality rate of beavers was about 30% in southeastern Newfoundland. A more detailed study was made of a population living in a 39-km2 (15-mi2) study area. This population had 20, 23, and 24 active colonies, 1958–1960. In 1961 it declined to 18 colonies. We removed the beavers in 1962. The replacement colonies, resulting initially from ingress, were 7 in 1962, 12 in 1963, 17 in 1964, and 15 in 1965. When the population was high in 1958–1960, the fertility of females was high (78%) but the litter size in 1960 appeared to be less than elsewhere. When the population declined in 1960–1961, productivity declined and some animals may have starved over winter. It was concluded that territorial behaviour spaces colonies, dispersing the population within the limits dictated by the availability of water and food resources. However, such a system did not prevent overutilization of food resources and decline of the population from reduced reproduction and increased mortality.