How to keep cool in a hot desert: Torpor in two species of free-ranging bats in summer

Bondarenco, Artiom; Körtner, Gerhard; Geiser, Fritz

doi:10.1080/23328940.2016.1214334

Cited by 22 publications

(8 citation statements)

References 31 publications

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“…When small mammals are euthermic and confronted with T a near the upper critical temperature, excess heat generated by metabolism or activity and the absorption of heat from the environment can quickly exceed their thermoregulatory capacities. Other tropical bats enter extended torpor, but only in the cooler morning hours and always accompanied by a reduction in body temperature, probably to save water in anticipation of responding to afternoon heat [33,34]. By contrast, M. commersoni entered hot torpor only under heat stress and maintained micro-bouts during cooler daytimes.…”

Section: Two Novel Modes Of Torpormentioning

confidence: 99%

Tropical bats counter heat by combining torpor with adaptive hyperthermia

Reher

Dausmann

2021

Proc. R. Soc. B.

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Many tropical mammals are vulnerable to heat because their water budget limits the use of evaporative cooling for heat compensation. Further increasing temperatures and aridity might consequently exceed their thermoregulatory capacities. Here, we describe two novel modes of torpor, a response usually associated with cold or resource bottlenecks, as efficient mechanisms to counter heat. We conducted a field study on the Malagasy bat Macronycteris commersoni resting in foliage during the hot season, unprotected from environmental extremes. On warm days, the bats alternated between remarkably short micro-torpor bouts and normal resting metabolism within a few minutes. On hot days, the bats extended their torpor bouts over the hottest time of the day while tolerating body temperatures up to 42.9°C. Adaptive hyperthermia combined with lowered metabolic heat production from torpor allows higher heat storage from the environment, negates the need for evaporative cooling and thus increases heat tolerance. However, it is a high-risk response as the torpid bats cannot defend body temperature if ambient temperature increases above a critical/lethal threshold. Torpor coupled with hyperthermia and micro-torpor bouts broaden our understanding of the basic principles of thermal physiology and demonstrate how mammals can perform near their upper thermal limits in an increasingly warmer world.

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Section: Two Novel Modes Of Torpormentioning

confidence: 99%

Tropical bats counter heat by combining torpor with adaptive hyperthermia

Reher

Dausmann

2021

Proc. R. Soc. B.

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“…24°C: [15][16][17]) or at night [18,19]. However, desert-dwelling species and others in hot climates may enter torpor at T a greater than 30°C [18,20]. The high T a s at which these bats begin to thermoconform approach the normal homoeothermic body temperature of most mammals (ca 36-38°C).…”

Section: Introductionmentioning

confidence: 99%

Heart rate reveals torpor at high body temperatures in lowland tropical free-tailed bats

et al. 2017

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Reduction in metabolic rate and body temperature is a common strategy for small endotherms to save energy. The daily reduction in metabolic rate and heterothermy, or torpor, is particularly pronounced in regions with a large variation in daily ambient temperature. This applies most strongly in temperate bat species (order Chiroptera), but it is less clear how tropical bats save energy if ambient temperatures remain high. However, many subtropical and tropical species use some daily heterothermy on cool days. We recorded the heart rate and the body temperature of free-ranging Pallas' mastiff bats (Molossus molossus) in Gamboa, Panamá, and showed that these individuals have low field metabolic rates across a wide range of body temperatures that conform to high ambient temperature. Importantly, low metabolic rates in controlled respirometry trials were best predicted by heart rate, and not body temperature. Molossus molossus enter torpor-like states characterized by low metabolic rate and heart rates at body temperatures of 32°C, and thermoconform across a range of temperatures. Flexible metabolic strategies may be far more common in tropical endotherms than currently known.

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“…Instead, Pavey et al (2020) suggested that the ability of dasyurids to enter torpor to save energy may decouple population dynamics from rainfall-driven primary productivity. Bats also use torpor on a regular basis, both after fire (Doty et al 2016) and in hot, dry environments (Bondarenco et al 2016), and this may reduce the effect of lower productivity during droughts on populations.…”

Section: Discussionmentioning

confidence: 99%

“…2016) and in hot, dry environments (Bondarenco et al . 2016), and this may reduce the effect of lower productivity during droughts on populations.…”

Section: Discussionmentioning

confidence: 99%

Landscape monitoring reveals initial trends in occupancy and activity of bats in multiple‐use forests

Law

Gonsalves

McConville³

et al. 2020

Austral Ecology

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Biodiversity monitoring is recognised as a key action for ecologically sustainable land use, but there are few examples of landscape programmes. We outline the first five years of biodiversity monitoring focusing on insectivorous bats in low rainfall, multiple-use forests and woodlands of the Pilliga, Australia. Using ultrasonic sampling over multiple nights, both on-and off-tracks, we identify annual trends in bat activity and occupancy and environmental covariates. Trends differed depending on whether occupancy or bat activity was the response variable. Site occupancy was almost 100% and remained stable and/or did not decline for most species nor diversity over the monitoring period, suggesting little variation in bat populations. In comparison, total activity was initially very high (567 passes night À1 on-track) and then declined by up to 40% in the following three years, but then fully recovered in the fifth year. This general pattern was evident both on-and off-tracks for most taxa, though activity was three times greater on-than off-track, highlighting the importance of these distinct habitat features for bats. Multivariate state-space (MARSS) models predicted, unexpectedly, that high winter rainfall prior to our surveys was negatively related to activity for many taxa. In contrast, disturbance from timber harvesting or fire had weak or no identifiable effects on trends in activity for most taxa. One exception was Chalinolobus picatus (threatened), whose occupancy off-tracks was negatively related to the extent of recent (<5 years) fire and to harvesting, though at the landscape scale, occupancy remained stable. This result, together with patterns for other bat taxa, suggests that disturbance effects were short-lived/dispersed and/or environmental mitigations were effective at maintaining bat populations at a landscape level. Annual monitoring highlighted annual variation in activity and its implications when setting a baseline for monitoring. We also discuss modifications to future monitoring effort, based on the existing five years of data.

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How to keep cool in a hot desert: Torpor in two species of free-ranging bats in summer

Cited by 22 publications

References 31 publications

Tropical bats counter heat by combining torpor with adaptive hyperthermia

Tropical bats counter heat by combining torpor with adaptive hyperthermia

Heart rate reveals torpor at high body temperatures in lowland tropical free-tailed bats

Landscape monitoring reveals initial trends in occupancy and activity of bats in multiple‐use forests

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