Coping with chaos: unpredictable food supplies intensify torpor use in an arid-zone marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata)

Abstract

, B. M. (2010). Coping with chaos: unpredictable food supplies intensify torpor use in an arid-zone marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata). Naturwissenschaften, 97 (6), 601-605.Coping with chaos: unpredictable food supplies intensify torpor use in an arid-zone marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata) AbstractThe severity, duration and amplitude of extreme weather events are forecast to intensify with current climate trends, over both long (e.g. seasonal) and short (e.g. daily) time-scales. As such, the predictability of food supplies for many small endotherms is likely to become increasingly important. Numerous small mammals and birds combat food shortages using torpor, a controlled reduction in metabolic rate and body temperature that helps lower their daily energy requirements. As such, torpor often has been cited as a key feature allowing some small endotherms to survive highly unpredictable climates, such as tropics or dry deserts, but mensurative demonstrations of this are lacking. We have shown here that when a small desert marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata), is offered unpredictable levels of daily food, they increase frequency of daily torpor and length of bouts compared with animals offered ad libitum food, but this was not found for animals offered a 70% food-restricted diet. Our data suggest that simple food restriction may not be sufficient for evaluating the efficacy of torpor as a strategy for managing unpredictable climates. AbstractThe severity, duration and amplitude of extreme weather events are forecast to intensify with current climate trends, over both long (e.g. seasonal) and short (e.g. daily) timescales. As such, the predictability of food supplies for many small endotherms is likely to become increasingly important. Numerous small mammals and birds combat food shortages using torpor, a controlled reduction in metabolic rate and body temperature that helps lower their daily energy requirements. As such, torpor often has been cited as a key feature allowing some small endotherms to survive highly unpredictable climates, such as tropics or dry deserts, but mensurative demonstrations of this are lacking. We have shown here that when a small desert marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata) is offered unpredictable levels of daily food they increase frequency of daily torpor and length of bouts compared with animals offered ad libitum food, but this was not found for animals offered a 70% food-restricted diet. Our data suggest that simple food restriction may not be sufficient for evaluating the efficacy of torpor as a strategy for managing unpredictable climates.

Unpredictable food availability induces metabolic and hormonal changes independent of food intake in a sedentary songbird

“…This framework suggests that periods of variable food intake due to variation in food abundance or interruptions in foraging due to increased 'risk' (such as predation or inclement weather) prompt individuals to regulate their body mass and energy usage (Bednekoff and Krebs, 1995;Witter et al, 1995; Cuthill et al, 2000). In birds and mammals, temporal variability in food availability is associated with fattening (Bednekoff and Krebs, 1995), an increase in daily torpor (Munn et al, 2010), increased or stabilized body mass (Witter et al, 1995; Cuthill et al, 2000) and less behavioral activity (Dall and Witter, 1998). These observations are consistent with the adaptive regulation hypothesis (Witter et al, 1995;Fauchald et al, 2004), which describes how animals coping with unpredictable food availability aim to decrease energetic expenditure and attenuate physiology that depletes energy reserves such as CORT secretion, thus promoting energy conservation, which conserves (or even increases) body mass.…”

Dietary composition and nutritional outcomes in two marsupials,Sminthopsis macrouraandS. crassicaudata

“…Males were used because a previous study demonstrated that they robustly adapt physiologically and behaviorally to variable amounts of food (Munn et al 2010). The animals were from a captive colony based at the University of Sydney, Sydney, New South Wales, Australia.…”

Minimum daily core body temperature in western grey kangaroos decreases as summer advances: a seasonal pattern, or a direct response to water, heat or energy supply?

“…That function would be congruent with morning T c being determined by time of year, which also determines season. We do know that food deprivation leads to a lower rest-phase T c in some birds and mammals (Kanizsai et al, 2009;, and that the response is likely driven by proximate signals related to energy intake (Maloney et al, 1999;Munn et al, 2010). Offering sheep a diet containing only 70% of maintenance energy requirements, as opposed to 100% of maintenance energy requirements, also resulted in a significant decrease in the restphase T c (S.K.M., L.C.R.M., A.F.…”