Journal Article

Stressful summers? Torpor expression differs between high- and low-latitude populations of bats

Zenon J Czenze, R. Mark Brigham, Anthony J. R Hickey and Stuart Parsons

in Journal of Mammalogy

Published on behalf of American Society of Mammalogists

Volume 98, issue 5, pages 1249-1255
Published in print October 2017 | ISSN: 0022-2372
Published online July 2017 | e-ISSN: 1545-1542 | DOI: https://dx.doi.org/10.1093/jmammal/gyx071
Stressful summers? Torpor expression differs between high- and low-latitude populations of bats

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  • Zoology and Animal Sciences
  • Animal Behaviour and Behavioural Ecology
  • Animal Ecology
  • Animal Physiology
  • Mammalogy

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Abstract

Variation in weather and food availability impacts the energy budgets of endotherms, with some species using torpor as an energy-saving strategy during periods of negative energy balance. We evaluated how latitudinal differences in energy balance relate to variation in torpor expression and roosting sociality between populations. We monitored summer skin temperatures (Tsk) of individuals from 2 populations of New Zealand lesser short-tailed bats (Mystacina tuberculata) separated by 6° of latitude using temperature telemetry. Although mean summer Ta was only < 1°C lower for the higher-latitude than lower-latitude population, individuals living at the higher-latitude site used torpor on 36% of observation days compared to 11% for lower-latitude bats. None of the recorded weather variables affected the propensity to enter torpor or torpor bout duration; however, the minimum torpid Tsk of bats positively correlated with daily minimum Ta. Roosts occupied by solitary bats were warmer than Ta, and temperatures within them fluctuated less than Ta. Higher-latitude individuals roosted solitarily (38%) more frequently than lower-latitude individuals (17%) and individuals from both populations exclusively used torpor while roosting solitarily. Arousals from torpor by higher-latitude bats coincided with sunset and not daily Ta maxima suggesting that bats were not fully exploiting advantages of passive rewarming. Site-specific roost choice and torpor patterns were apparent between M. tuberculata populations during summer, demonstrating that small differences in Ta differentially affect energetic strategy. The thermoregulatory behavior of species inhabiting latitudinal gradients in climate is highly plastic, likely to meet the specific challenges of their environment.

Keywords: Chiroptera; latitudinal variation; Mystacina tuberculata; thermoregulation; torpor

Journal Article.  5328 words.  Illustrated.

Subjects: Zoology and Animal Sciences ; Animal Behaviour and Behavioural Ecology ; Animal Ecology ; Animal Physiology ; Mammalogy

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