Status of Woodland Caribou as of December 1996 - population stable to declining. About 3500 Caribou in province of Alberta. Concern over maintenance of old-growth forest to provide critical winter habitat. Management of predation in some populations, improved population monitoring, and habitat protection are being addressed.

The two key climate related factors affecting caribou are snow and insects. Caribou have to work very hard during the winter months to forage for moss and lichen. During the brief summers they have to make the most of small tundra and shrubs. Any changes adversely affecting their environment on a consistent basis would threaten the herds.

When caribou dig in snow for moss and lichen, it is called "cratering". In areas of shallow snow, cratering could take only a few minutes to expose enough food for the day, but in deep snow or snow that is crusted over with ice from freezing rain, it could take 2 hours. Energy required per cratering stroke varies from 118 joules in light uncrusted snow to 219 joules in denser snow with a thin hard crust. Increased energy consumption and decreased food ability would increase starvation and decrease spring body fat, greatly reducing calf lactation and survival rates. A deeper winter snow pack also may make caribou more vulnerable to wolf attacks since lighter wolves can travel on snow crusts that carribou would sink through.

Insect harrassment by mosquitos and parasitic flies may significantly decrease foraging time. Insect harrassment is associated with temperatures of 13 degrees Celcius or higher, and wind speeds of less than 6 meters per second. Insect harrassment prevents foraging and increases energy requirements. The summer is a crucial time for calving and lactation, and also caribou fatten themselves for the coming winter. Warmer summers result in more insect harrassment, causing significant declines in body fat. The average temperature in the western Arctic in Canada and Alaska has been warming at a ratio of at least 0.5 degrees per decade over the last 30 years, a rate 3-5 times faster than the planet as a whole1. Most of this warming has occured in the winter and spring, but warming has also occured in the summer. This warming suggests that insect harrassment may already be increasing2.

An adequate amount of suitable habitat is also a key factor in maintaining viable caribou populations. Human use of caribou range can result in loss and fragmentation of important habitat elements such as winer ranges, calving areas or migration routes. Timber harvesting; oil and gas exploration and development, and coal mining all impact the caribou range.

[CARIBOU] [SITE MAP]

[1]Anne Gunn and Terje Skogland, 1997. "Responses of caribou and reindeer to global warming," in Walter C. Oechl, et.al.(eds.), Global Change and Arctic Terrestial Ecosystems, Springer-Verlag, New York, p.191.

[2] Stewart Cohen (ed.), 1997. The Mackenzie Basin Impact Study, Environment Canada, Ottawa; and BESIS 1996.