Range expansion of the winter tick into Northwest Territories, Canada

Ghost moose.
Photo credit: www.nrri.umn.edu

The winter tick, Dermacentor albipictus, is an important parasite of moose, white-tailed deer, elk and woodland caribou. Among these, moose are the most commonly and the most severely affected with individuals reported to host over 100,000 ticks. Hunters refer to heavily infested animals as “ghost moose” due to their pale color as a result of extensive hair loss caused by intensive grooming efforts in an attempt to remove the ticks. It is thought that winter ticks, together with other ecological stressors, are a significant factor in moose population dynamics. Climate change in northern Canada has increased the probability that winter ticks could extend their range northward and pose a similar threat to barren ground caribou, a valuable food resource for northern communities. This question was addressed by University of Calgary M.Sc. student, Cyntia Kashivakura.

In collaboration with subsistence hunters, community leaders and Renewable Resource Councils from the Sahtu, Government of Northwest Territories and local wildlife officers, Cyntia was able to collect moose and barren ground caribou hides from several communities across the region. Ticks were collected, identified and counted by digesting these hides in a potassium hydroxide solution. Five of 30 moose hides were positive for winter ticks while all 25 barren ground caribou were negative. This study confirmed that the winter tick had extended its range from a previous maximum limit of 62^oN in the southern Yukon to 66°N in the Sahtu Settlement Region. Even though the prevalence of winter ticks on moose at this latitude was lower than observed in more southerly regions of Canada it is important to continue monitoring for this parasite to detect changes in prevalence and intensity of infestation. Further monitoring of both woodland and barren ground caribou should be undertaken to determine whether these populations are infested and what impact infestation may have on the animals and the communities that depend on them for subsistence.

For more information on the winter tick, please visit http://www.ccwhc.ca/wildlife_health_topics/winter_tick/wintertick.php

Severe winter tick infestation on a moose
Photo credit: Cynthia Kashivakura