Torpor and metabolism in hummingbirds

Krüger, K.; Prinzinger, Roland; Schuchmann, Karl‐Ludwig

doi:10.1016/0300-9629(82)90275-4

Cited by 108 publications

(60 citation statements)

References 7 publications

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“…Nevertheless, in gray mouse lemurs, T b s during torpor were relatively low compared to other daily heterotherms, for most of which minimum T b s ranged between 10 and 30°C (Geiser and Ruf 1995). Minimum T b s falling as low as 5°C during daily torpor are only known from the honey possum (Tarsipes rostratus) (Withers et al 1990), or 6.5°C measured in the torpid humming bird species Oreotrochilus estella (Krüger et al 1982). During torpor, animals generally preserve their T b s within 2°C above the T a (Hudson 1973;Ortmann 1989;Wang 1978).…”

Section: Discussionmentioning

confidence: 96%

Daily torpor in the gray mouse lemur ( Microcebus murinus ) in Madagascar: energetic consequences and biological significance

Schmid

2000

Oecologia

165

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Patterns and energetic consequences of spontaneous daily torpor were measured in the gray mouse lemur (Microcebus murinus) under natural conditions of ambient temperature and photoperiod in a dry deciduous forest in western Madagascar. Over a period of two consecutive dry seasons, oxygen consumption (VO) and body temperature (T ) were measured on ten individuals kept in outdoor enclosures. In all animals, spontaneous daily torpor occurred on a daily basis with torpor bouts lasting from 3.6 to 17.6 h, with a mean torpor bout duration of 9.3 h. On average, body temperatures in torpor were 17.3±4.9°C with a recorded minimum value of 7.8°C. Torpor was not restricted to the mouse lemurs' diurnal resting phase: entries occurred throughout the night and arousals mainly around midday, coinciding with the daily ambient temperature maximum. Arousal from torpor was a two-phase process with a first passive, exogenous heating where the T of animals increased from the torpor T minimum to a mean value of 27.1°C before the second, endogenous heat production commenced to further raise T to normothermic values. Metabolic rate during torpor (28.6±13.2 ml O h) was significantly reduced by about 76% compared to resting metabolic rate (132.6±50.5 ml O h). On average, for all M. murinus individuals measured, hypometabolism during daily torpor reduced daily energy expenditure by about 38%. In conclusion, all these energy-conserving mechanisms of the nocturnal mouse lemurs, with passive exogenous heating during arousal from torpor, low minimum torpor T s, and extended torpor bouts into the activity phase, comprise an important and highly adapted mechanism to minimize energetic costs in response to unfavorable environmental conditions and may play a crucial role for individual fitness.

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Section: Discussionmentioning

confidence: 96%

Daily torpor in the gray mouse lemur ( Microcebus murinus ) in Madagascar: energetic consequences and biological significance

Schmid

2000

Oecologia

165

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“…When hummingbirds enter torpor, metabolic rate decreases and body temperature (T b ) drops as much as 20Њ-30ЊC. Use of torpor results in a substantial energy savings by lowering nighttime energy expenditures (Lasiewski 1963;Krüger et al 1982;Hiebert 1990). However, the use of torpor by hummingbirds may have potential costs.…”

Section: Introductionmentioning

confidence: 98%

Influence of Normal Daytime Fat Deposition on Laboratory Measurements of Torpor Use in Territorial versus Nonterritorial Hummingbirds

Powers

Brown

Hook

2003

Physiological and Biochemical Zoology

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Fat deposition and torpor use in hummingbirds exhibiting distinct foraging styles should vary. We predicted that dominant territorial hummingbirds will use torpor less than subordinate nonterritorial species because unrestricted access to energy by territory owners allows for fat storage. Entry into torpor was monitored using open-flow respirometry on hummingbirds allowed to accumulate fat normally during the day. Fat accumulation was measured by solvent fat extraction. Territorial blue-throated hummingbirds (Lampornis clemenciae) had the highest fat accumulation and used torpor only 17% of the time. Fat storage by L. clemenciae averaged 26% of lean dry mass (LDM) in 1995 and 18% in 1996, similar to that measured for other nonmigratory birds. Fat storage by magnificent hummingbirds (Eugenes fulgens; trapliner) and black-chinned hummingbirds (Archilochus alexandri; nectar robber) averaged 19% and 16% of LDM, respectively, and they used torpor frequently (64% and 92% of the time, respectively). All species initiated torpor if total body fat dropped below 10% of LDM, indicating the existence of a torpor threshold. The ability of L. clemenciae to store enough fat to support nighttime metabolism is likely an important benefit of territoriality. Likewise, frequent torpor use by subordinates suggests that natural restrictions to energy intake can impact their energy budget, necessitating energy conservation by use of torpor.

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“…Torpor is a more extreme form of hypothermia that is often characterized by a relatively large drop in body temperature and greatly reduced behavioural responsiveness [11][12][13]. Torpor is most often observed in relatively small species with comparatively low energy costs of rewarming [12] and is especially pronounced in species which rely on ephemeral food sources, such as nectar or insects [8].…”

Section: Introductionmentioning

confidence: 99%

Nocturnal hypothermia impairs flight ability in birds: a cost of being cool

Carr

Lima

2013

Proc. R. Soc. B.

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Many birds use regulated drops in night-time body temperature (T b ) to conserve energy critical to winter survival. However, a significant degree of hypothermia may limit a bird's ability to respond to predatory attack. Despite this likely energy-predation trade-off, the behavioural costs of avian hypothermia have yet to be examined. We thus monitored the nocturnal hypothermia of mourning doves (Zenaida macroura) in a laboratory setting in response to food deprivation. Nocturnal flight tests were used to quantify the flight ability of hypothermic doves. Many hypothermic doves (39% of tests) could not fly while carrying a small weight, but could do so after quickly warming up to typical daytime T b . Doves that were unable to fly during their first test were more hypothermic than those that could fly, with average T b reductions of 5.38C and 3.38C, respectively, but there was no overall indication of a threshold T b reduction beyond which doves were consistently incapable of flight. These results suggest that energy-saving hypothermia interferes with avian antipredator behaviour via a reduction in flight ability, likely leading to a trade-off between energy-saving hypothermia and the risk of predation.

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Torpor and metabolism in hummingbirds

Cited by 108 publications

References 7 publications

Daily torpor in the gray mouse lemur ( Microcebus murinus ) in Madagascar: energetic consequences and biological significance

Daily torpor in the gray mouse lemur ( Microcebus murinus ) in Madagascar: energetic consequences and biological significance

Influence of Normal Daytime Fat Deposition on Laboratory Measurements of Torpor Use in Territorial versus Nonterritorial Hummingbirds

Nocturnal hypothermia impairs flight ability in birds: a cost of being cool

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