Winter body temperature patterns in free-ranging Cape ground squirrel, Xerus inauris: no evidence for torpor.
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.
Wilson
Wendy A
WA
Department of Zoology, University of Cape Town, Rondebosch, Cape Town 7701, South Africa. wendy@walkwithmeerkats.co.za
O'Riain
M Justin
MJ
Hetem
Robyn S
RS
Fuller
Andrea
A
Fick
Linda G
LG
D000064:Acclimatization; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D001831:Body Temperature; D002940:Circadian Rhythm; D003080:Cold Temperature / Q000009:adverse effects*; D005260:Female; D007774:Lactation / Q000378:metabolism*; D008297:Male; D009043:Motor Activity; D012589:Sciuridae / Q000378:metabolism*; D012621:Seasons; D013019:South Africa; D022722:Thermogenesis / Q000502:physiology*; D013997:Time Factors
J S Afr Vet Assoc. 2009 Dec;80(4):276-7
20458874
J Therm Biol. 2001 Jun;26(3):159-163
11240220
J Comp Physiol B. 1998 May;168(4):303-12
9646507
Comp Biochem Physiol A Mol Integr Physiol. 2006 Jan;143(1):42-9
16309938
Comp Biochem Physiol A Mol Integr Physiol. 2007 Nov;148(3):645-50
17826203
Physiol Biochem Zool. 2003 Jan-Feb;76(1):72-83
12695988
J Comp Physiol B. 2008 Sep;178(7):887-97
18523787
Behaviour. 1974;49(3):227-67
4597405
J Comp Physiol B. 1988;158(2):151-6
3170823
J Comp Physiol B. 1998 Apr;168(3):233-9
9591364
J Comp Physiol B. 2007 Nov;177(8):885-92
17674010
Oecologia. 2004 Jan;138(2):202-9
14608499
J Comp Physiol B. 1998 Oct;168(7):540-8
9810718
J Comp Physiol B. 2007 Aug;177(6):667-77
17487493
J Exp Biol. 2002 Jul;205(Pt 14):2099-105
12089213
Physiol Behav. 1994 Feb;55(2):361-9
8153179
Exp Physiol. 2000 Mar;85(2):209-17
10751518
Oecologia. 2002 Nov;133(3):307-314
28466221
J Appl Physiol (1985). 1997 Sep;83(3):837-44
9292471
Annu Rev Physiol. 2004;66:239-74
14977403
Physiol Biochem Zool. 2004 Mar-Apr;77(2):285-96
15095248
Am J Physiol. 1998 Jan;274(1):R46-51
9458897
Comp Biochem Physiol A Comp Physiol. 1977;56(1A):59-67
11064
J Mammal. 1972 Nov;53(4):774-90
4654241
Physiol Biochem Zool. 2007 Jan-Feb;80(1):138-45
17160886
Am J Physiol. 1957 Jan;188(1):103-12
13402948
Folia Primatol (Basel). 2006;77(6):465-76
17053331
J Comp Physiol B. 2003 Feb;173(1):55-60
12592443
Physiol Biochem Zool. 2006 May-Jun;79(3):454-67
16691512