Warming up for sleep? — Ground squirrels sleep during arousals from hibernation

Daan, Serge; Barnes, Brian M.; Strijkstra, Arjen M.

doi:10.1016/0304-3940(91)90276-y

Cited by 200 publications

(154 citation statements)

References 15 publications

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“…The most parsimonious explanation for the apparent preference for normothermia during resting in long-eared bats is to facilitate the numerous biochemical and physiological processes that are retarded by a low T b and MR during torpor bouts. For example, bats may arouse to allow for restorative sleep processes, protein synthesis or even the digestion of food captured the previous night (Storey and Storey, 1990;Daan et al, 1991;van Breukelen and Martin, 2002b).…”

Section: Discussionmentioning

confidence: 99%

Timing of the daily temperature cycle affects the critical arousal temperature and energy expenditure of lesser long-eared bats

Turbill

Körtner

Geiser

2008

Journal of Experimental Biology

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SUMMARYDaily patterns of body temperature (T b ) and energy expenditure in heterothermic endotherms are affected by changes in ambient temperature (T a ) and selection of suitable microclimates, yet most laboratory studies employ constant T a to measure metabolic rates. In particular, exposure to a daily temperature cycle, even within rest shelters, may be important in timing of torpor and arousal and determining resting energy costs in wild animals. We tested how captive bats (Nyctophilus geoffroyi; 7 g) exposed to a diurnal T a fluctuation (between 13°C and 27°C), similar to natural conditions in their summer tree roosts, adjusted the timing of daily arousals. To distinguish the effects of T a and passive rewarming from time of the day, we shifted the heating phase to commence at 06:00 h, 09:00 h or 12:00 h on each day. Bats entered torpor overnight and aroused the next day at a time corresponding to rising T a and passive rewarming. The critical T a (and torpid T b ) for arousal was not fixed, however, but was lower when heating occurred later in the rest phase, providing the first evidence that the critical arousal T a is affected by time of the day. Bats re-entered torpor in response to cooling late in the afternoon, yet always aroused at lights off. A period of normothermic thermoregulation was therefore closely synchronised with maximum daily T a , indicating a trade-off between the benefits and energetic costs of normothermia during resting. Our experiment clearly shows that a daily T a cycle affects the thermoregulatory behaviour and energetics of these small bats. More generally, these results demonstrate the critical influence of behavioural decisions on the daily energy expenditure of small heterothermic mammals.

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Section: Discussionmentioning

confidence: 99%

Timing of the daily temperature cycle affects the critical arousal temperature and energy expenditure of lesser long-eared bats

Turbill

Körtner

Geiser

2008

Journal of Experimental Biology

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“…Three predictions from this 'arousal for sleep' hypothesis have been supported by empirical results: (1) animals sleep most of the time [2,10], (2) a sleep debt, reflected by the non-rapideye-movement (NREM) sleep electroencephalogram (EEG) slow wave power, decreases during the arousal episode [2,10], and (3) there is evidence that sleep debt increases with duration of torpor [3,5,9,10]. It is known for several hibernators that spontaneous arousal episodes occur more frequently when ambient temperature (T a ) is higher [11].…”

mentioning

confidence: 86%

Ambient temperature during torpor affects NREM sleep EEG during arousal episodes in hibernating European ground squirrels

Strijkstra¹,

Daan²

1997

Neuroscience Letters

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“…Many different hypotheses attempting to explain periodic arousals have been proposed (Strumwasser, 1959;Galster and Morrison, 1970;Baumber et al, 1971;Daan et al, 1991;Thomas and Cloutier, 1992;Németh et al, 2010), as reviewed by Thomas and Geiser (Thomas and Geiser, 1997). One hypothesis proposes that during hibernation there is an accumulation of metabolic wastes, such as ketone bodies, and a need to replenish energy-rich substrates (Galster and Morrison, 1970;Baumber et al, 1971).…”

Section: Introductionmentioning

confidence: 99%

Waking to drink: rates of evaporative water loss determine arousal frequency in hibernating bats

Ben-Hamo

Muñoz‐Garcia

Williams

et al. 2013

Journal of Experimental Biology

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SUMMARYBats hibernate to cope with low ambient temperatures (T a ) and low food availability during winter. However, hibernation is frequently interrupted by arousals, when bats increase body temperature (T b ) and metabolic rate (MR) to normothermic levels. Arousals account for more than 85% of a batʼs winter energy expenditure. This has been associated with variation in T b , T a or both, leading to a single testable prediction, i.e. that torpor bout length (TBL) is negatively correlated with T a and T b . T a and T b were both found to be correlated with TBL, but correlations alone cannot establish a causal link between arousal and T b or T a . Because hydration state has also been implicated in arousals from hibernation, we hypothesized that water loss during hibernation creates the need in bats to arouse to drink. We measured TBL of bats (Pipistrellus kuhlii) at the same T a but under different conditions of humidity, and found an inverse relationship between TBL and total evaporative water loss, independent of metabolic rate, which directly supports the hypothesis that hydration state is a cue to arousal in bats.

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Warming up for sleep? — Ground squirrels sleep during arousals from hibernation

Cited by 200 publications

References 15 publications

Timing of the daily temperature cycle affects the critical arousal temperature and energy expenditure of lesser long-eared bats

Timing of the daily temperature cycle affects the critical arousal temperature and energy expenditure of lesser long-eared bats

Ambient temperature during torpor affects NREM sleep EEG during arousal episodes in hibernating European ground squirrels

Waking to drink: rates of evaporative water loss determine arousal frequency in hibernating bats

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