Long‐Term Range Recession and the Persistence of Caribou in the Taiga

Abstract

Abstract: Spatial patterns can help in understanding the decline and future prospects of threatened species, but the dynamics of range retraction have not been applied to these fundamental questions. I analyzed long‐term changes in occupancy by taiga‐dwelling caribou ( Rangifer tarandus caribou ) to estimate their rate of disappearance and time to extirpation in Ontario, Canada. Patterns of range recession, 1880–1990, indicated that half of historic woodland caribou range has been lost, a rate of disappearance of 34,800 km2 per decade, and a northward range recession of 34 km per decade. The mean metapopulation density, the abundance of discrete winter groups, was one group per 1,900 km2, suggesting an average loss of 18 caribou wintering areas per decade during this period. There was a strong coincidence between the recent southern limits of caribou occupancy and the northern front of forest harvesting, implying an anthropogenic agent of decline. The estimated time to extirpation of forest‐dwelling caribou in Ontario, inferred from the sustained rate of disappearance, was 91 years ( 95% confidence interval: 57–149 years ). The persistence of woodland caribou may depend on spatial separation from human incursion.