Dynamics of an Introduced Caribou Population

Abstract

Caribou (Rangifer tarandus groenlandicus) were hunted to extinction on Southampton Island (Northwest Territories, Canada) by 1953. In 1967, 48 caribou were captured on neighbouring Coats Island and released on Southampton Island. We documented the population dynamics, group size and composition, and distribution of caribou from introduction to 1991, based on aerial and ground survey data. The number of one-year-old caribou grew from 38 in 1967 to 13 700 (SE = 1600) in 1991. The corresponding annual growth rate was 27.6%, with no indication of any decline in the rate with increasing population density. Contrary to models describing the irruption of ungulates, the population dispersed rapidly after introduction to use all suitable habitats. Southampton caribou did not show high winter mortality in some years as did caribou on neighbouring Coats Island, where caribou density was higher, suggesting that the effect of adverse weather on the dynamics of northern insular caribou populations is dependent on animal density.Key words: caribou, Rangifer, population dynamics, irruption, distribution, Northwest Territories