CAUSES OF MORTALITY

Information gathered about Vancouver Island marmots indicates that survival rates have declined and the frequency of high-mortality episodes has increased. Wolves, cougars, and golden eagles prey upon marmots and are responsible for significant losses at some of the colonies. There is no evidence to suggest that reproductive rates have declined.


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EFFECTS OF LOGGING

The most important effect of forestry was to concentrate the population, thereby increasing the risk of mortality from predation and jeopardizing the metapopulation model the Vancouver Island marmots had relied upon for millennia.

When clearcut logging reached higher elevations surrounding marmot colonies, the marmot population experienced a short-term gain as marmots colonized the newly created habitat. (To a dispersing marmot, recently cut forests at higher elevations resembled natural habitat. There are large openings, flowers to eat, deep soil to dig, and good visibility.)

However, this short-term gain was followed quickly by a dramatic decline as survival in both the clearcut colonies and the natural colonies plummeted. The formation of the clearcut colonies cause a decline in the natural colonies by diverting marmots which were dispersing, preventing them from re-populating existing natural colonies or establishing new colonies in traditional habitat.

Survival in the clearcut colonies was compromised by regrowth of trees and other vegetation, which provided cover for predators.
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Recovery Strategy