LEHMER, Erin M; Colorado State University: A Rare Incident of Hibernation in Free-Ranging Black-Tailed Prairie Dogs

In the natural environment, hibernating sciurids generally remain dormant during winter and enter numerous torpor bouts from the time of first immergence in fall until emergence in spring. This is in contrast to free-ranging black-tailed prairie dogs (Cynomys ludovicianus), which remain active throughout winter but periodically enter short and shallow bouts of torpor. Although previous studies have suggested that factors including weather and diet quality can trigger torpor in this species, the extent to which facultative torpor is influenced by external environmental conditions or by innate circadian timing mechanisms is unknown. While investigating body temperature patterns of black-tailed prairie dogs from colonies across an elevational gradient in northern Colorado, I observed a single population (L1) displaying torpor patterns that strongly resemble those of free-ranging hibernators. This population experienced multiple bouts of torpor that increased in length and depth as winter progressed. Inter-torpor arousal periods were brief with animals maintaining euthermic body temperatures for <24 h. Environmental conditions did not appear to have a large influence on deep torpor in this population, as prairie dogs monitored from other colonies in close proximity to L1 remained euthermic for the majority of winter and entered shallow bouts of torpor at infrequent intervals. Likewise, factors including diet quality, composition of stored body fat, and weather do not seem to be primary stimuli for hibernation patterns experienced by prairie dogs on colony L1. My preliminary results suggest that phenotypic plasticity in torpor patterns of black-tailed prairie dogs may be caused by physiological differences between populations, rather than by environmental and habitat differences.