Competition between Eurasian red and introduced Eastern grey squirrels: the energetic significance of body-mass differences.
Daily energy expenditure (DEE) was 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.
Bryce
J M
JM
Wildlife Conservation Research Unit, Department of Zoology, Oxford University, South Parks Road, Oxford OX1 3PS, UK. jennybryce@btinternet.com
Speakman
J R
JR
Johnson
P J
PJ
Macdonald
D W
DW
D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight; D032462:Cycadopsida; D003903:Deuterium; D004734:Energy Metabolism; D004777:Environment; D019684:Magnoliopsida; D010103:Oxygen Isotopes; D012589:Sciuridae / Q000502:physiology*; D013045:Species Specificity; D014197:Trees; D014867:Water / Q000378:metabolism
D010103:Oxygen Isotopes; D014867:Water; D003903:Deuterium