FACTORS AFFECTING EPIZOOTICS OF WINTER TICKS AND MORTALITY OF MOOSE

Abstract

Die-offs of moose (Alces alces) associated with, or attributed to, winter ticks (Dermacentor albipictus) are widespread and have been reported since the early part of the last century. Extrinsic factors such as weather and vegetative structure, and host factors such as moose density and, indirectly, tick-induced damage to the hair coat, were examined in an attempt to predict related problems for moose. The proposal that warmer and shorter winters result in increased survival of adult female ticks dropping off moose in March and April, and increased tick populations on moose the following winter, was generally confirmed. Annual changes in hair damage and loss on moose, which are documented from the air, coincided with annual changes in numbers of ticks on moose, providing managers with a survey tool to monitor and estimate changing numbers of ticks. Tick numbers lagged 1 year behind moose numbers in Elk Island National Park over a 12-year period, and many moose died when numbers of both were high. Several widespread, concurrent die-offs suggest extrinsic influences play a role, possibly independent of moose density. The lack of objective and continuous data sets should guide future research efforts.