WINTER TICKS ON MOOSE AND OTHER UNGULATES: FACTORS INFLUENCING THEIR POPULATION SIZE

Abstract

Research on northern populations of winter ticks (Dermacentor albipictus), particularly that relating to sources of variation in tick numbers, is reviewed. Mean numbers of ticks on moose (Alces alces) populations from 3 provinces were 32,527. Intrinsic sources of variation in size of tick populations included potential avoidance of sessile aggregations of larvae by moose in autumn, defensive grooming, and host death. Winter tick-induced premature loss of winter hair, which resulted from grooming, was prevalent and widespread throughout the range of moose in North America. Temporal progression and extent of hair-loss, and a proposed mechanism for that loss are reviewed. Extrinsic sources of variation in size of tick populations included effect of autumn weather on concentrations of tick larvae, and magpies on survival of shed adult female ticks. Reports of dead or debilitated moose with large numbers of ticks are numerous in Alberta and elsewhere. Weather winter ticks regulate moose numbers is not known, but moose are certainly the most severely affected host of winter ticks.