Demographic characteristics of circumpolar caribou populations: ecotypes, ecological constraints, releases, and population dynamics

Data on the status of caribou {Rangifer tarandus) herds throughout the circumpolar region during the last 20 years were obtained from the literature and personal communication with researchers. Information was analysed in relation to ecotype (insular, montane, barren-ground, and woodland/forest), population status (increasing, stable, decreasing), herd size, human impact, and temporal change in number. The data support the conclusions (1) that each ecotype is exposed to different ecological constraints and releases, which influence the demographic characteristics of their populations, (2) that subspecific (genotypic) classification does not explain the demographic characteristics of caribou populations, (3) that insular and montane ecotype populations are relatively stable, (4) that barren-ground ecotype herds are currently experiencing synchronous population growth throughout the circumpolar region and may undergo population cycles, (5) that in North America, the woodland caribou subspecies (genotype) forms the largest barren-ground ecotype herd in the world and is not endangered nor at risk, (6) that populations of woodland/forest ecotypes are declining and threatened throughout the circumpolar region, possibly due to the interaction of human disturbance and predation, and (7) that no relationship exists between herd size and risk of being classified as threatened by researchers.