Competition between Eurasian red and introduced Eastern grey squirrels: the energetic significance of body-mass differences

J M Bryce, J R Speakman, P J Johnson, D W Macdonald

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Daily energy expenditure (DEE),vas measured in sympatric populations of red and grey squirrels using the doubly labelled water technique. Grey squirrels had significantly higher DEEs than red squirrels. However, the difference between the species was not separable from the effects of body mass on DEE. The DEEs of both species were in accordance with published allometric predictions incorporating body mass and ambient temperature. The differences in energetic requirements and social dominance, both consequences of body size, may represent means by which grey squirrels exert more interspecific competition on red squirrels than do conspecifics, potentially driving populations below viable levels in some sites.

Original languageEnglish
Pages (from-to)1731-1736
Number of pages6
JournalProceedings of the Royal Society of London. B, Biological Sciences
Publication statusPublished - 2001


  • body mass
  • conservation
  • daily energy expenditure
  • doubly labelled
  • ater
  • red squirrel
  • grey squirrel
  • sciurus-vulgaris
  • foraging behavior
  • conifer woodland
  • activity budget
  • carolinensis
  • poulation
  • habitats
  • demography
  • abundance
  • patterns

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