Near-Total Loss of Caribou on South-Central Canadian Arctic Islands and the Role of Seasonal Migration in their Demise

Abstract

Caribou (Rangifer tarandus) on the south-central Canadian Arctic Islands (Prince of Wales, Somerset, and Russell islands) declined by 98% sometime between 1980 and 1995—a near-total loss of a known genetically distinctive group of Arctic Island caribou. In contrast, caribou on the adjacent Boothia Peninsula seemingly increased by 38% from 1985 to 1995, while experiencing heavy annual hunting pressure. Our evaluation leads us to three primary conclusions. 1) It would have been biologically impossible for the estimated 1985 population on Boothia Peninsula (4831 ± 543 SE caribou one year old or older) to sustain the estimated annual harvest of 1100 one year old or older animals without continual annual ingress of caribou from beyond Boothia Peninsula. Our analysis of the 540 possible combinations of population parameters indicates that at any size within ± 2 SE of the 1985 estimate (3745–5917 caribou one year old or older), the Boothia Peninsula caribou population would have gone to “mathematical extirpation”: 99% of the combinations by 1995 and 100% by 1999. 2) The continued unsustainable level of harvest was masked by the annual winter infusion of migrant caribou onto Boothia Peninsula from Prince of Wales, Somerset, and Russell islands. 3) Caribou persisted on Boothia Peninsula, but only because of the simultaneous near elimination of the Arctic Island caribou ecotype in the Prince of Wales, Somerset, and Russell islands geographic population. This caribou resource cannot be properly conserved without adequate monitoring and periodic estimates of population sizes and annual harvest rates throughout the entire Prince of Wales, Somerset, and Russell islands-Boothia Peninsula complex.