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 whole 1 . 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 increasing 2 . 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.