Influence of winter ticks (Dermacentor albipictus) and temperature on recumbent behaviour of moose (Alces alces) calves

Abstract

Heavy infestations with winter ticks ( Dermacentor albipictus (Packard, 1869)) have been associated with mortality of moose ( Alces alces (Linnaeus, 1758)). Recumbency is an obligate behaviour for moose when ruminating and when conserving core body heat in cold weather. Recumbent behaviours were used to establish impacts of ticks and ambient temperatures on moose calves during the winter. Calves ( n = 12) were evenly divided into no-tick, low-tick, and high-tick groups. Recumbency bout duration increased over the winter but was independent of the tick group. The probability of ruminating decreased during warm temperatures for infested moose in the early stages of infestation. Legs tucked tightly decreased with increasing ambient temperature for all groups, and all groups had a higher probability of head down when ambient conditions were colder. The greatest differences in behaviour were between moose of the high-tick group and other moose. During the most active tick phases when ambient conditions dropped below −10 °C, moose of the high-tick group had a higher probability of being recumbent with their head down and legs tucked tight to the body. Energy conservation, irritation from ticks, and the impact of body condition are the three primary stimuli that most likely influenced recumbent postures of moose calves in this study.