During June, we perform ground-based composition counts to estimate calf production, recruitment, and adult sex ratio. We have radiocollared over 100 muskoxen in order to document seasonal shifts in distribution and habitat use, and to estimate survival and cause-specific mortality.

Following the 1969 release, muskoxen increased rapidly in the Arctic Refuge, reaching a peak of approximately 400 individuals in 1986. This was followed by expansion of the population’s range into contiguous areas of north-central Alaska and northwestern Canada. We subsequently implemented cooperative surveys with the Alaska Department of Fish and Game (ADFG), Parks Canada, and Yukon Department of Environment to monitor the entire population. The number of muskoxen within the Refuge declined slightly, and then remained stable at about 325 from 1987 to 1998.

We observed a precipitous decline in abundance of muskoxen within the Arctic Refuge beginning in 1999. In 2003, we estimated that fewer than 50 muskoxen occurred within Refuge boundaries. We attribute this decline to shifts in distribution, low calf recruitment, and decreased adult survival. In a recent cooperative study with ADFG (Reynolds et al. 2002), we determined that predation by grizzly bears was a significant and increasing source of mortality for muskoxen. The negative effect of predation on survival may be exacerbated by environmental conditions that limit access to forage, such as icing events and deep, persistent snows. We are continuing to monitor the status of this muskox population and investigate factors responsible for observed trends.