Torpor in an African caprimulgid, the freckled nightjar <i>Caprimulgus tristigma</i>

McKechnie, Andrew E.; Ashdown, Robert A. M.; Christian, Murray; Brigham, R. Mark

doi:10.1111/j.2007.0908-8857.04116.x

Cited by 58 publications

(43 citation statements)

References 23 publications

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“…Similar variation in minimum T skin occurred in Freckled Nightjar population from the Magaliesberg (McKechnie et al 2007), although in the latter study T skin was consistently higher in males (generally above 30°C), and only females entered deep torpor. In contrast, variation in minimum T skin in our study population did not appear to be related to gender, with males as well as females entering deep torpor.…”

Section: Discussionsupporting

confidence: 68%

“…The Freckled Nightjar is a nocturnal aerial insectivore which occurs in rocky habitats over much of sub-Saharan Africa (Spottiswoode and Jackson 2005). Freckled Nightjars can enter torpor (McKechnie et al 2007) and activity levels are correlated with ambient light levels and temperature (Ashdown and McKechnie 2008).…”

Section: Methodsmentioning

confidence: 99%

“…We investigated thermoregulatory patterns of Freckled Nightjars during June and July We obtained telemetric measurements of skin temperature (T skin ) for Freckled Nightjars, following the methods of McKechnie et al (2007). Skin temperature is widely used to asses thermoregulatory patterns of birds, and although T skin is not exactly equal to T b , it is a robust proxy of nocturnal T b in birds (Brigham et al 2000;McKechnie et al 2007;Smit and McKechnie 2010).…”

Section: Methodsmentioning

confidence: 99%

“…Skin temperature is widely used to asses thermoregulatory patterns of birds, and although T skin is not exactly equal to T b , it is a robust proxy of nocturnal T b in birds (Brigham et al 2000;McKechnie et al 2007;Smit and McKechnie 2010). The temperature-sensitive radio-transmitters (2.5g, model PD-2T, Holohil Systems, Carp, Ontario, Canada) were pre-calibrated in a temperature-controlled water bath at temperatures between 5° and 45°C, using an NISTtraceable mercury thermometer.…”

Section: Methodsmentioning

confidence: 99%

“…1.) for each individual (Boyles et al 2011;McKechnie et al 2007) and then estimated the extent of heterothermy for each bird on each night using a simple metric called the Heterothermy Index (HI):…”

Section: Methodsmentioning

confidence: 99%

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Torpor in Dark Times: Patterns of Heterothermy Are Associated with the Lunar Cycle in a Nocturnal Bird

et al. 2011

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Many studies have shown that endotherms become more heterothermic when the costs of thermoregulation are high and/or when limited energy availability constrains thermoregulatory capacity. However, the roles of many ecological variables, including constraints on foraging opportunities and/or success, remain largely unknown. To test the prediction that thermoregulatory patterns should be related to foraging opportunities in a heterothermic endotherm we examined the relationship between the lunar cycle and heterothermy in Freckled Nightjars (Caprimulgus tristigma), which are visually orienting, nocturnal insectivores that are dependent on ambient light to forage. This model system provides an opportunity to assess whether variation in foraging

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Section: Discussionsupporting

confidence: 68%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Torpor in Dark Times: Patterns of Heterothermy Are Associated with the Lunar Cycle in a Nocturnal Bird

et al. 2011

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Combinations of reproductive, individual, and weather effects best explain torpor patterns among female little brown bats (Myotis lucifugus)

Besler

Broders

2019

Ecology and Evolution

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Heterothermic mammals can use torpor, a state of metabolic suppression, to conserve energy during times of limited food and poor environmental conditions. Females may use torpor throughout gestation and lactation; however, there are associated physiological and ecological costs with potential fitness consequences. Previous studies have controlled for, but not quantified the impact of interindividual variation on torpor patterns and understanding this may provide insight on why certain thermoregulatory responses are employed. The objective of this study was to identify and quantitatively characterize the intrinsic variables and weather conditions that best explain variation in torpor patterns among individual female little brown bats, Myotis lucifugus . We used temperature‐sensitive radio‐transmitters affixed to females to measure skin temperature patterns of 35 individuals roosting in bat boxes in the spring and summer. We used Bayesian multi‐model inference to rank a priori‐selected models and variables based on their explanatory power. Reproductive condition and interindividual effects best explained torpor duration and depth, and weather best explained torpor frequency. Of the reproductive conditions, lactating females used torpor for the shortest durations and at shallower depths (i.e., smallest drop in minimum T sk ), while females in early spring (i.e., not‐obviously‐pregnant) used torpor for the longest and deepest. Among individuals, the greatest difference in effects on duration occurred between pregnant individuals, suggesting interindividual variation within reproductive condition. Increases in precipitation and wind were associated with a higher probability of torpor use. Our results provide further support that multiple variables explain torpor patterns and highlight the importance of including individual effects when studying thermoregulatory patterns in heterothermic species. OPEN RESEARCH BADGES This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://doi.org/10.5061/dryad.c04tj85 .

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Heterothermy in two mole‐rat species subjected to interacting thermoregulatory challenges

Boyles

Verburgt²,

McKechnie³

et al. 2011

J. Exp. Zool.

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Maintaining a high and constant body temperature (T(b) ) is often viewed as a fundamental benefit of endothermy, but variation in T(b) is likely the norm rather than an exception among endotherms. Thus, attempts to elucidate which factors cause T(b) of endotherms to deviate away from the T(b) that maximizes performance are becoming more common. One approach relies on an adaptive framework of thermoregulation, used for a long time to predict variation in T(b) of ectotherms, as a starting point to make predictions about the factors that should lead to thermoregulatory variation in endotherms. Here we test the predictions that when confronted with thermoregulatory challenges endotherms should (1) become more heterothermic, (2) lower their T(b) setpoint, and/or (3) increase behavioral thermoregulation (e.g., activity levels or social thermoregulation). We exposed two species of relatively homeothermic mole-rats to two such challenges: (a) ambient temperatures (T(a)) well below the thermoneutral zone and (b) increased heat loss caused by the removal of dorsal fur. In general, our results support the adaptive framework of endothermic thermoregulation with each species conforming to some of the predictions. For example, Mashona mole-rats (Fukomys darlingi) increased heterothermy as T(a) decreased, highveld mole-rats (Cryptomys hottentotus pretoriae) displayed lower T(b) 's after shaving, and both species increased behavioral thermoregulation as T(a) decreased. This suggests that there is some merit in extending the adaptive framework to endotherms. However, none of the three predictions we tested was supported under all experimental conditions, reiterating that attempts to determine universal factors causing variation in T(b) of endotherms may prove challenging.

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Torpor in an African caprimulgid, the freckled nightjar Caprimulgus tristigma

Cited by 58 publications

References 23 publications

Torpor in Dark Times: Patterns of Heterothermy Are Associated with the Lunar Cycle in a Nocturnal Bird

Torpor in Dark Times: Patterns of Heterothermy Are Associated with the Lunar Cycle in a Nocturnal Bird

Combinations of reproductive, individual, and weather effects best explain torpor patterns among female little brown bats (Myotis lucifugus)

Heterothermy in two mole‐rat species subjected to interacting thermoregulatory challenges

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