Winter and Summer Torpor in a Free-Ranging Subtropical Desert Bat: The Fishing Myotis (<i>Myotis vivesi</i>)

Salinas, R V B; Herrera, Mariana; Flores‐Martínez, José Juan; Johnston, Dave S.

doi:10.3161/150811014x687288

Cited by 14 publications

(3 citation statements)

References 31 publications

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“…Wind speed may also rapidly shift in intensity throughout the night, which the mean wind condition variable will not have accounted for in our analyses. Wind speed has previously been found to negatively impact activity level in insectivorous bats (Avery 1985;Wolcott and Vulinec 2012) as well as increasing torpor expression in fishing bats (Salinas et al 2014). The suggested mechanisms behind the effect of wind is that it functions as a source of increasing flight cost (Norberg 1990) and may also affect prey abundance by decreasing the number of flying insects (McGeachie 1989;Møller 2013).…”

Section: Discussionmentioning

confidence: 99%

“…Most studies investigating environmental effects on nightly bat activity tend to measure activity based upon capture rates, echolocation frequencies or emergence numbers from roosts. In this study, we instead explore the effect of nightly conditions on individual torpor use, which as a direct physiological response differs from indirect measures of activity levels (Wojciechowski et al 2007;Salinas et al 2014). Torpor use should thus tell us more about how these bats evaluate prospective foraging conditions and the relative costs and benefits to their energy budget and life history in order to employ torpor at specific times.…”

Section: Introductionmentioning

confidence: 99%

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Nightly torpor use in response to weather conditions and individual state in an insectivorous bat

2021

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Torpor is a well-known energy conservation strategy in many mammal and bird species. It is often employed when environmental conditions are unfavourable to maximize survival probabilities. However, torpor often carries with it the physiological costs of a low body temperature and of rewarming in addition to potential missed opportunities for foraging. Therefore, we hypothesised that decision making regarding when to use torpor should reflect the most important environmental conditions for species distributions, and thus how they may be impacted by ongoing climate change. We investigated how weather conditions affect nightly torpor patterns in the nocturnal insectivorous Australian eastern long-eared bat (Nyctophilus bifax). By measuring the skin temperature of 37 free-ranging individuals, we confirmed that torpor was used more frequently during the winter and at subtropical compared to tropical locations. Using mixed-effect models we show that lower ambient temperatures were the main driver of individual torpor use, probably due to lower roost temperatures and prey availability. However, increased rain, wind and humidity, and decreasing barometric pressure, as well as brighter moonlight, also led to more time spent torpid per night. We suggest that bats evaluate multiple environmental cues to make decisions regarding torpor use versus active foraging based upon their expectations of the energetic benefits, prey availability and relative predation risk. Interactions between some of these effects and body mass (whilst controlling for forearm length) indicate that individual variation in body size and/or state-dependent effects of energy reserves also partly determined the use of nightly torpor in these bats.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Nightly torpor use in response to weather conditions and individual state in an insectivorous bat

2021

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“…For example, strong winds, strong surf and low ambient temperature during winter months may limit fish-eating myotis foraging behaviour at the time of year when they rely most on a crustacean diet. Fish-eating myotis employ torpor during this period of potentially restricted food intake (Salinas R. et al, 2014). Both heterothermy and low energy reserves may impact digestive effort at the time when relative digestive costs may be greatest.…”

Section: Discussionmentioning

confidence: 99%

The cost of digestion in the fish-eating myotis (Myotis vivesi)

Welch

Otálora-Ardila

Flores‐Martínez

2015

Journal of Experimental Biology

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Flying vertebrates, such as bats, face special challenges with regards to the throughput and digestion of food. On the one hand, as potentially energy-limited organisms, bats must ingest and assimilate energy efficiently in order to satisfy high resting and active metabolic demands. On the other hand, the assimilation of nutrients must be accomplished using a digestive tract that is, compared with that of similarly sized non-flying vertebrates, significantly shorter. Despite these competing demands, and the relative breadth of dietary diversity among bats, little work has been done describing the cost of digestion, termed 'specific dynamic action' (SDA). Here, we provide the first systematic assessment of the SDA response in a bat, the fisheating myotis (Myotis vivesi). Given the shorter digestive tract and the relatively higher resting and active metabolic rates of bats in general, and based on anecdotal published evidence, we hypothesized that the SDA response in fish-eating myotis would be dependent on meal size and both significantly more brief and intense than in small, nonflying mammals. In agreement with our hypothesis, we found that the peak metabolic rate during digestion, relative to rest, was significantly higher in these bats compared with any other mammals or vertebrates, except for some infrequently eating reptiles and amphibians. Additionally, we found that the magnitude and duration of the SDA response were related to meal size. However, we found that the duration of the SDA response, while generally similar to reported gut transit times in other small bats, was not substantially shorter than in similarly sized non-flying mammals.

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Hibernation in bats (Mammalia: Chiroptera) did not evolve through positive selection of leptin

Lazzeroni

Burbrink

Simmons

2018

Ecology and Evolution

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Temperature regulation is an indispensable physiological activity critical for animal survival. However, relatively little is known about the origin of thermoregulatory regimes in a phylogenetic context, or the genetic mechanisms driving the evolution of these regimes. Using bats as a study system, we examined the evolution of three thermoregulatory regimes (hibernation, daily heterothermy, and homeothermy) in relation to the evolution of leptin, a protein implicated in regulation of torpor bouts in mammals, including bats. A threshold model was used to test for a correlation between lineages with positively selected lep, the gene encoding leptin, and the thermoregulatory regimes of those lineages. Although evidence for episodic positive selection of lep was found, positive selection was not correlated with lineages of heterothermic bats, a finding that contradicts results from previous studies. Evidence from our ancestral state reconstructions suggests that the most recent common ancestor of bats used daily heterothermy and that the presence of hibernation is highly unlikely at this node. Hibernation likely evolved independently at least four times in bats—once in the common ancestor of Vespertilionidae and Molossidae, once in the clade containing Rhinolophidae and Rhinopomatidae, and again independently in the lineages leading to Taphozous melanopogon and Mystacina tuberculata. Our reconstructions revealed that thermoregulatory regimes never transitioned directly from hibernation to homeothermy, or the reverse, in the evolutionary history of bats. This, in addition to recent evidence that heterothermy is best described along a continuum, suggests that thermoregulatory regimes in mammals are best represented as an ordered continuous trait (homeothermy ← → daily torpor ← → hibernation) rather than as the three discrete regimes that evolve in an unordered fashion. These results have important implications for methodological approaches in future physiological and evolutionary research.

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Winter and Summer Torpor in a Free-Ranging Subtropical Desert Bat: The Fishing Myotis (Myotis vivesi)

Cited by 14 publications

References 31 publications

Nightly torpor use in response to weather conditions and individual state in an insectivorous bat

Nightly torpor use in response to weather conditions and individual state in an insectivorous bat

The cost of digestion in the fish-eating myotis (Myotis vivesi)

Hibernation in bats (Mammalia: Chiroptera) did not evolve through positive selection of leptin

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