Temperature alone is insufficient to understand hibernation energetics

Energy conservation has long been a focal point in hibernation research. A
long-standing assumption is that ambient temperature (Ta) largely defines
the rate of energy expenditure because of well-known relationships between
Ta, metabolic rate and frequency of arousal from torpor. Body condition
and humidity also affect energy expenditure but are usually considered
secondary factors. We held tricolored bats (Perimyotis subflavus) in
captivity under multiple environmental conditions to directly compare the
importance of Ta, fat mass and humidity for hibernation energy
expenditure. Fat mass was the best predictor of female mass loss, followed
by Ta and humidity. However, males had less fat and adopted a more
energetically conservative hibernation strategy. Our results demonstrate
that understanding the evolution of behavior, physiology and ecology of
hibernation requires disentangling the relative contributions of multiple
drivers of hibernation energetics, and that Ta is not always the most
important factor driving energy expenditure.