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The Influence of Foraging Mode and Arid Adaptation on the Basal Metabolic Rates of Burrowing Mammals

Craig R. White
Physiological and Biochemical Zoology: Ecological and Evolutionary Approaches
Vol. 76, No. 1 (January/February 2003), pp. 122-134
DOI: 10.1086/367940
Stable URL: http://www.jstor.org/stable/10.1086/367940
Page Count: 13
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
The Influence of Foraging Mode and Arid Adaptation on the Basal Metabolic Rates of Burrowing Mammals
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Abstract

Abstract Two competing but nonexclusive hypotheses to explain the reduced basal metabolic rate (BMR) of mammals that live and forage underground (fossorial species) are examined by comparing this group with burrowing mammals that forage on the surface (semifossorial species). These hypotheses suggest that the low BMR of fossorial species either compensates for the enormous energetic demands of subterranean foraging (the cost‐of‐burrowing hypothesis) or prevents overheating in closed burrow systems (the thermal‐stress hypothesis). Because phylogentically informed allometric analysis showed that arid burrowing mammals have a significantly lower BMR than mesic ones, fossorial and semifossorial species were compared within these groups. The BMRs of mesic fossorial and semifossorial mammals could not be reliably distinguished, nor could the BMRs of large (>77 g) arid fossorial and semifossorial mammals. This finding favours the thermal‐stress hypothesis, because the groups appear to have similar BMRs despite differences in foraging costs. However, in support of the cost‐of‐burrowing hypothesis, small (<77 g) arid fossorial mammals were found to have a significantly lower BMR than semifossorial mammals of the similar size. Given the high mass‐specific metabolic rates of small animals, they are expected to be under severe energy and water stress in arid environments. Under such conditions, the greatly reduced BMR of small fossorial species may compensate for the enormous energetic demands of subterranean foraging.

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