Winter body temperature patterns in free-ranging Cape ground squirrel, Xerus inauris: no evidence for torpor |
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Authors: | Wendy A Wilson M Justin O’Riain Robyn S Hetem Andrea Fuller Linda G Fick |
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Institution: | (1) Department of Zoology, University of Cape Town, Rondebosch, Cape Town, 7701, South Africa;(2) Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa |
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Abstract: | The body temperature (T
b) of Cape ground squirrels (Xerus inauris, Sciuridae) living in their natural environment during winter has not yet been investigated. In this study we measured abdominal
T
b of eight free-ranging Cape ground squirrels over 27 consecutive days during the austral winter. Mean daily T
b was relatively stable at 37.0 ± 0.2°C (range 33.4 to 40.2°C) despite a marked variation in globe temperature (T
g) (range −7 to 37°C). Lactating females (n = 2) consistently had a significantly higher mean T
b (0.7°C) than non-lactating females (n = 3) and males. There was a pronounced nychthemeral rhythm with a mean active phase T
b of 38.1 ± 0.1°C and a mean inactive phase T
b of 36.3 ± 0.3°C for non-lactating individuals. Mean daily amplitude of T
b rhythm was 3.8 ± 0.2°C. T
b during the active phase closely followed T
g and mean active phase T
b was significantly correlated with mean active phase T
g (r
2 = 0.3–0.9; P < 0.01). There was no evidence for daily torpor or pronounced hypothermia during the inactive phase, and mean minimum inactive
phase T
b was 35.7 ± 0.3°C for non-lactating individuals. Several alternatives (including nocturnal huddling, an aseasonal breeding
pattern and abundant winter food resources) as to why Cape ground squirrels do not employ nocturnal hypothermia are discussed. |
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Keywords: | |
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