The winter ecology of Cape Churchill caribou (Rangifer tarandus ssp.)

Abstract

Aspects of snow conditions, plant community use, and feeding habits were examined for caribou occupying the Cape Churchill Wildlife Management Area. Studies were carried out over each of the 1989-90 and 1990-91 snow seasons. Attempts were made to interrelate feeding habits and plant community use with changing snow conditions based on 7 snow stations set up within four taiga and three tundra plant communities. Fundamental differences between taiga and tundra snow conditions are also discussed. Plant communities were described based on quadrat and point quarter methods, prior to snowfall, within each of four taiga and three tundra plant community snow stations. Snow conditions at snow stations and caribou feeding sites were quantified through the excavation and examination of snow profiles... Taiga and tundra snow conditions are fundamentally different. This was primarily due to the effects of wind on the more exposed tundra and the relative lack of wind in the taiga... Cape Churchill caribou displayed a wide use of plant communities that varied both throughout the snow seasons and between them. Snow conditions within taiga plant communities differed both between themselves over both snow seasons, and differed between the two snow seasons. Tundra plant communities also displayed variability over the same periods though not as severe as taiga sites. Cape Churchill caribou did however remain in feeding sites beyond threshold levels if suitable alternate plant communities were not available. These data imply that conventional wildlife management techniques used to determine caribou range tend dramatically to underestimate actual requirements. Through the long term field monitoring of representative plant community snow conditions and winter habitat use by caribou, a more realistic estimate of caribou range can be achieved.