SHIVERING BY CAPTIVE MOOSE INFESTED WITH WINTER TICKS

Abstract

Occurence and rate of shivering were measured to assess thermoregulatory responses of captive moose (Alces alces) infested with winter ticks (Dermacentor albipictus). Shivering was observed on 47 occasions in 5 of 8 infested moose calves from October to April; in contrast, 4 moose calves not infested with winter ticks did not shiver under identical weather conditions. Only 5 shivering bouts occurred from October to March, all on a single day. The other 42 shivering bouts occurred in April with bouts lasting 1–103 min. During the April bouts, ambient temperature was 1– 4 °C (42 of 42), maximum wind speed was ≤12 km/h (38 of 42), and it was raining (30 of 42). Shivering was associated with 23–44% hair loss in April, but not during cold weather in mid-winter despite 5–10% hair loss in March. Maintaining stable core body temperature during late winter-early spring could compromise the energetic balance of wild free-ranging moose with extensive hair loss and abundant ticks, in conditions equivalent to or worse than measured in this study.