Cool running: locomotor performance at low body temperature in mammals

Rojas, A. Daniella; Körtner, Gerhard; Geiser, Fritz

doi:10.1098/rsbl.2012.0269

Cited by 50 publications

(41 citation statements)

References 27 publications

(34 reference statements)

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“…Similarly, a number of species of tenrec have been found to be active at T b as low as 25°C (Crompton et al, 1978;Eisenberg and Gould, 1969;Poppitt et al, 1994). Activity at low T b has similarly been observed in monotremes (Kuchel, 2003), marsupials (Rojas et al, 2012;Turner et al, 2012), placental mammals (Wooden and Walsberg, 2004) and birds (Merola-Zwartjes and Ligon, 2000). As a consequence, differentiating torpor from normothermy in these species using T b alone is complicated (Brice et al, 2002;Canale et al, 2012).…”

Section: Research Articlementioning

confidence: 72%

Increased homeothermy during reproduction in a basal placental mammal

Levesque

Lovegrove

2014

Journal of Experimental Biology

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Homeothermic endothermy, the maintenance of a high and stable body temperature (T b ) using heat produced by elevated metabolism, is energetically expensive. There is increasing evidence that the earliest endotherms were heterotherms that, rather than maintaining strict homeothermy, allowed T b to fluctuate with large variations between active and rest-phase T b . The high level of homeothermy observed in modern mammals is therefore likely to have evolved from an ancestral heterothermic state. One of the hypotheses for the evolution of endothermy is that homeothermy allows for greater energetic output during reproduction (parental care model). We tested this hypothesis by measuring metabolic rates over a range of ambient temperatures in both reproductive and non-reproductive greater hedgehog tenrecs (Setifer setosus), a physiologically primitive mammal from Madagascar. Tenrecs have some of the lowest metabolic rates and highest levels of T b variability of any mammal and are therefore good models of the ancestral eutherian state. During pregnancy and lactation, there was an increase in metabolism and T b below the thermoneutral zone, accompanied by a decrease in T b variability. The lower critical limit of the thermoneutral zone was estimated at ~25°C. However, whereas increases in resting metabolism were substantial below 20°C (up to 150% higher during reproduction), daytime rest-phase ambient temperatures at the study site rarely reached equivalent low levels. Thus, S. setosus provide an example for how relatively low-cost increases in homeothermy could have led to substantial increases in fitness by allowing for the faster production of young. The mechanisms necessary for increases in thermogenesis during reproduction would have further benefited the development of homeothermy in mammals.

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Section: Research Articlementioning

confidence: 72%

Increased homeothermy during reproduction in a basal placental mammal

Levesque

Lovegrove

2014

Journal of Experimental Biology

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“…Considering the energetic advantages, basking behaviour might be expected for hamsters with a high T b , but for torpid hamsters with a T b near or below 20°C this may incur a potential cost because movement is slowed and the risk of predation is increased (Rojas et al, 2012). However, basking has been observed in wild dasyurid marsupials not only during rest in the afternoon but also in the morning when animals are rewarming from torpor and therefore must remain concealed from diurnal predators (Geiser et al, 2002;Warnecke et al, 2008;Rojas et al, 2012), as would be the case for white P. sungorus on or near snow.…”

Section: Discussionmentioning

confidence: 99%

“…However, basking has been observed in wild dasyurid marsupials not only during rest in the afternoon but also in the morning when animals are rewarming from torpor and therefore must remain concealed from diurnal predators (Geiser et al, 2002;Warnecke et al, 2008;Rojas et al, 2012), as would be the case for white P. sungorus on or near snow. Important in this regard is that in the past, differences in fur colour among dasyurid populations were considered to be of little importance from energetic, thermal and camouflage points of view because animals were considered to be nocturnal.…”

Section: Discussionmentioning

confidence: 99%

“…Although movement at low torpor T b obviously is slowed, the hamsters in our study were never far from their tube refuge and must have been aware of their surroundings, otherwise they would not have moved under the heat lamp. In the wild, small marsupial mammals often bask at low T b between 15 and 20°C during rewarming from torpor, but they always do so near a soil crack or rock crevice refuge and even at low T b can move fast enough to cover small distances and avoid predation (Rojas et al, 2012). Deeply torpid animals are often stiff and immobile (Lyman et al, 1982) and therefore there must be a reason for this ability of hamsters to move at low T b .…”

Section: Discussionmentioning

confidence: 99%

“…Basking behaviour in the morning has been observed in several torpid desert or savanna mammals with T b as low as 15°C (Geiser et al, 2002(Geiser et al, , 2004Warnecke et al, 2008;Thompson et al, 2015). This is despite the fact that many of these species are widely considered to be entirely nocturnal and risk predation during the day, especially when movement is slowed (Rojas et al, 2012). Basking during rewarming is particularly important during daily torpor, which usually lasts <12 h within a 24 h cycle and therefore requires many potentially costly arousals (Ruf and Geiser, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Basking hamsters reduce resting metabolism, body temperature and energy costs during rewarming from torpor

Geiser

Gasch

Bieber

et al. 2016

Journal of Experimental Biology

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Basking can substantially reduce thermoregulatory energy expenditure of mammals. We tested the hypothesis that the largely white winter fur of hamsters (Phodopus sungorus), originating from Asian steppes, may be related to camouflage to permit sun basking on or near snow. Winter-acclimated hamsters in our study were largely white and had a high proclivity to bask when resting and torpid. Resting hamsters reduced metabolic rate (MR) significantly (>30%) when basking at ambient temperatures (T a ) of ∼15 and 0°C. Interestingly, body temperature (T b ) also was significantly reduced from 34.7±0.6°C (T a 15°C, not basking) to 30.4±2.0°C (T a 0°C, basking), which resulted in an extremely low (<50% of predicted) apparent thermal conductance. Induced torpor (food withheld) during respirometry at T a 15°C occurred on 83.3±36.0% of days and the minimum torpor MR was 36% of basal MR at an average T b of 22.0±2.6°C; movement to the basking lamp occurred at T b <20.0°C. Energy expenditure for rewarming was significantly reduced (by >50%) during radiant heat-assisted rewarming; however, radiant heat per se without an endogenous contribution by animals did not strongly affect metabolism and T b during torpor. Our data show that basking substantially modifies thermal energetics in hamsters, with a drop of resting T b and MR not previously observed and a reduction of rewarming costs. The energy savings afforded by basking in hamsters suggest that this behaviour is of energetic significance not only for mammals living in deserts, where basking is common, but also for P. sungorus and probably other cold-climate mammals.

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Quantifying Torpor

Geiser

2021

Fascinating Life Sciences

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Cool running: locomotor performance at low body temperature in mammals

Cited by 50 publications

References 27 publications

Increased homeothermy during reproduction in a basal placental mammal

Increased homeothermy during reproduction in a basal placental mammal

Basking hamsters reduce resting metabolism, body temperature and energy costs during rewarming from torpor

Quantifying Torpor

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