Preparing for inactivity: how insectivorous bats deposit a fat store for hibernation

J R Speakman, A Rowland

Research output: Contribution to journalArticle

73 Citations (Scopus)

Abstract

During late autumn insectivorous bats must deposit a fat store to cover their energy demands throughout the period of hibernation, yet the density of aerial insects by this time has already declined from its peak in midsummer. Krzanowski (1961) suggested that bats an able to deposit a fat store by manipulating their energy expenditure; specifically by selecting cold roosting locations rather than warm roosts, and depressing their body temperatures during the day roosting period. It was hypothesized that these behavioural changes result in very low daily energy demands, and despite reduced food intake the animals are still able to gain body fat. We made several tests of this hypothesis. First, we explored the thermo-selection behaviour of long-eared bats (Plecotus auritus) in the summer and in the pre-hibernal period. We found that in summer bats preferred temperatures of about 32-35 degrees (about thermoneutral), but in the pre-hibernal period they preferred much colder temperatures of about 10 degrees. Second, using open-flow respirometry we found that in the cold pre-hibernal bats entered torpor for an average of 14 h each day. Compared with bats held at 30 degrees (that did not go torpid), the bats at 7 degrees expended less energy. The extent of saving was sufficient to positively affect their mass balance, despite the fact that bats at lower temperature also had reduced digestive efficiencies. Our findings support the hypothesis that during the prl-hibernal period insectivorous bats manipulate their mass balance primarily by alterations in their energy expenditure, specifically utilizing energy-sparing mechanisms such as torpor.

Original languageEnglish
Pages (from-to)123-131
Number of pages9
JournalProceedings of the Nutrition Society
Volume58
Publication statusPublished - 1999

Keywords

  • hibernation
  • thermo-selection
  • torpor
  • energy expenditure
  • insectivorous bats
  • EARED PLECOTUS-AURITUS
  • EVAPORATIVE WATER-LOSS
  • GROUND-SQUIRRELS
  • MYOTIS-LUCIFUGUS
  • ENERGY BUDGETS
  • BROWN BATS
  • FOOD
  • REQUIREMENTS
  • EFFICIENCY
  • CHIROPTERA

Cite this

Preparing for inactivity: how insectivorous bats deposit a fat store for hibernation. / Speakman, J R ; Rowland, A .

In: Proceedings of the Nutrition Society, Vol. 58, 1999, p. 123-131.

Research output: Contribution to journalArticle

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AB - During late autumn insectivorous bats must deposit a fat store to cover their energy demands throughout the period of hibernation, yet the density of aerial insects by this time has already declined from its peak in midsummer. Krzanowski (1961) suggested that bats an able to deposit a fat store by manipulating their energy expenditure; specifically by selecting cold roosting locations rather than warm roosts, and depressing their body temperatures during the day roosting period. It was hypothesized that these behavioural changes result in very low daily energy demands, and despite reduced food intake the animals are still able to gain body fat. We made several tests of this hypothesis. First, we explored the thermo-selection behaviour of long-eared bats (Plecotus auritus) in the summer and in the pre-hibernal period. We found that in summer bats preferred temperatures of about 32-35 degrees (about thermoneutral), but in the pre-hibernal period they preferred much colder temperatures of about 10 degrees. Second, using open-flow respirometry we found that in the cold pre-hibernal bats entered torpor for an average of 14 h each day. Compared with bats held at 30 degrees (that did not go torpid), the bats at 7 degrees expended less energy. The extent of saving was sufficient to positively affect their mass balance, despite the fact that bats at lower temperature also had reduced digestive efficiencies. Our findings support the hypothesis that during the prl-hibernal period insectivorous bats manipulate their mass balance primarily by alterations in their energy expenditure, specifically utilizing energy-sparing mechanisms such as torpor.

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