Breeding area fidelity and dispersal patterns of bull caribou, Wrangell-St. Elias National Park and Preserve, Alaska

PROJECT DESCRIPTION:
The Mentasta Caribou Herd, which ranges within the northern portions of Wrangell-St. Elias National Park and Preserve, declined from about 3,200 caribou in 1987 to about 540 animals currently. Recent closures of subsistence hunting of caribou within Wrangell-St. Elias as a result of the declines in Mentasta Caribou generated substantial management controversy for the National Park Service. Further, the Mentasta Herd mixes with the much large Nelchina Herd (approximately 40,000 caribou) on winter ranges northeast of Wrangell-St. Elias. The goal of minimizing harvest of Mentasta caribou has frustrated efforts by the Alaska Department of Fish and Game to manage the size of the Nelchina Herd through intensive winter harvests. The foundation for managing the Mentasta Caribou Herd is the premise that it is distinct from the Nelchina Herd. In particular, harvest quotas for the Mentasta Herd are based in part on the adult sex ratio determined within the autumn range of known Mentasta females. However, there is anecdotal evidence that bulls originating in the Nelchina Herd may occur within the Mentasta range during the fall and represent a large source population to replace bulls harvested within Wrangell-St. Elias National Park and Preserve. We know very little about the movements, range use patterns, or survival patterns of bull caribou in general. Caribou research throughout North America has focused on productivity, survival, and habitat selection of cows and their dependent calves with little or no attention to males. Caribou herds are defined geographically by the aggregations of cows during calving. Radio telemetry studies over the last decade have shown very little interchange of females among herds. However, interchange by males could be occurring undetected because they have not been the focus of any research. If herd interchange by males does occur, it is most likely to happen in situations where herds overlap seasonally, such as the Mentasta and Nelchina Herds. Detecting interchange by adult males among herds, dispersal of short-yearling bulls to another herd, or greater genetic similarities among bulls from adjacent herds than occurs within cows would greatly change the conventional views of herd distinctness. We propose to address these research issues by evaluating seasonal range fidelity of bull caribou radio collared within the range of the Mentasta Herd in autumn, investigating the existence and magnitude of dispersal of male calves born on the Mentasta Range, and comparing the genetic relatedness of bulls from both herds. Given that the adult sex ratio within the Mentasta Herd continues to stay higher than that indicated by the poor recruitment of calves, evidence of no strong affinity to breeding ranges by adult bulls, detectable dispersal of male calves from the Mentasta Herd, and/or a high degree of genetic similarity among bulls in the 2 herds would be evidence that significant interchange of bulls is occurring. Further, this study will contribute significantly to the understanding of the ecology and population dynamics of male caribou in northern North America.