A global heterothermic continuum in mammals

Boyles, Justin G.; Thompson, Amy B.; McKechnie, Andrew E.; Malan, Ezit; Humphries, Murray M.; Careau, Vincent

doi:10.1111/geb.12077

Cited by 100 publications

(97 citation statements)

References 34 publications

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“…Similar to the vast differences in the daily T b amplitudes, torpor patterns are highly variable both among and within species (Fig. 2) [10,29,36,53,97,98]. However, a decrease in T b during winter can not only be observed in heterothermic species, but also, to a lesser degree, in homeothermic species.…”

Section: Seasonality and Unpredictability Of Mammalian T Bmentioning

confidence: 54%

“…This is a relatively common phenomenon in non-hibernating mammals, but most studies focus on change in insulation rather than change in T b as an energy saving mechanism [93][94][95]. A large body of work exists assessing the evolution of thermal flexibility in ectotherms (reviewed by [15]), but similar approaches have yet to be applied systematically to endotherms [10,11].…”

Section: Daily Variability In Mammalian T Bmentioning

confidence: 99%

“…Furthermore, by focusing entirely on strict categorical variables, many studies have ignored the potential adaptive benefits to small, non-torpid changes in T b [7,91]. It is clear that there exists a high degree of variability in both the level of T b (often reported as mean T b or set-point T b ) and the precision with which it is regulated [10,29,36,46]. Furthermore, it is probable that some degree of heterothermy, and likely variable torpor expression, was the ancestral condition in mammals, and that the high degree of homeothermy in extant species evolved via a highly heterothermic ancestor [36,53,114].…”

Section: Seasonality and Unpredictability Of Mammalian T Bmentioning

confidence: 99%

“…As we seek to improve the accuracy of predicting organismal responses to changes in climate, emphasis is being placed on mechanistic models that rely on an in-depth understanding of the thermoregulatory physiology and energetics of a species [1][2][3][4][5][6]. To date, however, the bulk of these models have been built and tested on ectothermic organisms [7][8][9], while research on endotherms has lagged behind [10]. This is partly due to deficiencies in understanding the mechanisms of the relationship between environmental temperatures and energy metabolism in endotherms [8,[11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…Variable T b is widespread in mammals, and both habitat and evolutionary history have a large influence on the thermoregulatory characteristics of endotherms [10,29,36]. Energy usage in relation to climate is further affected by phylogeny, activity level, microclimate selection, reproductive status, and energy availability [13,21,[37][38][39][40].…”

Section: Introductionmentioning

confidence: 99%

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Modelling mammalian energetics: the heterothermy problem

Levesque

Nowack

Stawski

2016

Clim Chang Responses

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Global climate change is expected to have strong effects on the world's flora and fauna. As a result, there has been a recent increase in the number of meta-analyses and mechanistic models that attempt to predict potential responses of mammals to changing climates. Many models that seek to explain the effects of environmental temperatures on mammalian energetics and survival assume a constant body temperature. However, despite generally being regarded as strict homeotherms, mammals demonstrate a large degree of daily variability in body temperature, as well as the ability to reduce metabolic costs either by entering torpor, or by increasing body temperatures at high ambient temperatures. Often, changes in body temperature variability are unpredictable, and happen in response to immediate changes in resource abundance or temperature. In this review we provide an overview of variability and unpredictability found in body temperatures of extant mammals, identify potential blind spots in the current literature, and discuss options for incorporating variability into predictive mechanistic models.

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Section: Seasonality and Unpredictability Of Mammalian T Bmentioning

confidence: 54%

Section: Daily Variability In Mammalian T Bmentioning

confidence: 99%

Section: Seasonality and Unpredictability Of Mammalian T Bmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Modelling mammalian energetics: the heterothermy problem

Levesque

Nowack

Stawski

2016

Clim Chang Responses

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Predation can shape the cascade interplay between heterothermy, exploration and maintenance metabolism under high food availability

Boratyński,

Iwińska,

Wirowska

et al. 2024

Ecology and Evolution

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Maintenance metabolism as the minimum energy expenditure needed to maintain homeothermy (a high and stable body temperature, Tb), reflects the magnitude of metabolic machinery and the associated costs of self‐maintenance in endotherms (organisms able to produce heat endogenously). Therefore, it can interact with most, if not all, organismal functions, including the behavior–fitness linkage. Many endothermic animals can avoid the costs of maintaining homeothermy and temporally reduce Tb and metabolism by entering heterothermic states like torpor, the most effective energy‐saving strategy. Variations in BMR, behavior, and torpor use are considered to be shaped by food resources, but those conclusions are based on research studying these traits in isolation. We tested the effect of ecological contexts (food availability and predation risk) on the interplay between the maintenance costs of homeothermy, heterothermy, and exploration in a wild mammal—the yellow‐necked mouse. We measured maintenance metabolism as basal metabolic rate (BMR) using respirometry, distance moved (exploration) in the open‐field test, and variation in Tb (heterothermy) during short‐term fasting in animals captured at different locations of known natural food availability and predator presence, and with or without supplementary food resources. We found that in winter, heterothermy and exploration (but not BMR) negatively correlated with natural food availability (determined in autumn). Supplementary feeding increased mouse density, predation risk and finally had a positive effect on heterothermy (but not on BMR or exploration). The path analysis testing plausible causal relationships between the studied traits indicated that elevated predation risk increased heterothermy, which in turn negatively affected exploration, which positively correlated with BMR. Our study indicates that adaptive heterothermy is a compensation strategy for balancing the energy budget in endothermic animals experiencing low natural food availability. This study also suggests that under environmental challenges like increased predation risk, the use of an effective energy‐saving strategy predicts behavioral expression better than self‐maintenance costs under homeothermy.

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Does metabolism constrain bird and mammal ranges and predict shifts in response to climate change?

Buckley

Khaliq

Swanson

et al. 2018

Ecology and Evolution

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Mechanistic approaches for predicting the ranges of endotherms are needed to forecast their responses to environmental change. We test whether physiological constraints on maximum metabolic rate and the factor by which endotherms can elevate their metabolism (metabolic expansibility) influence cold range limits for mammal and bird species. We examine metabolic expansibility at the cold range boundary (MECRB) and whether species’ traits can predict variability in MECRB and then use MECRB as an initial approach to project range shifts for 210 mammal and 61 bird species. We find evidence for metabolic constraints: the distributions of metabolic expansibility at the cold range boundary peak at similar values for birds (2.7) and mammals (3.2). The right skewed distributions suggest some species have adapted to elevate or evade metabolic constraints. Mammals exhibit greater skew than birds, consistent with their diverse thermoregulatory adaptations and behaviors. Mammal and bird species that are small and occupy low trophic levels exhibit high levels of MECRB. Mammals with high MECRB tend to hibernate or use torpor. Predicted metabolic rates at the cold range boundaries represent large energetic expenditures (>50% of maximum metabolic rates). We project species to shift their cold range boundaries poleward by an average of 3.9° latitude by 2070 if metabolic constraints remain constant. Our analysis suggests that metabolic constraints provide a viable mechanism for initial projections of the cold range boundaries for endotherms. However, errors and approximations in estimating metabolic constraints (e.g., acclimation responses) and evasion of these constraints (e.g., torpor/hibernation, microclimate selection) highlight the need for more detailed, taxa‐specific mechanistic models. Even coarse considerations of metabolism will likely lead to improved predictions over exclusively considering thermal tolerance for endotherms.

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A global heterothermic continuum in mammals

Cited by 100 publications

References 34 publications

Modelling mammalian energetics: the heterothermy problem

Modelling mammalian energetics: the heterothermy problem

Predation can shape the cascade interplay between heterothermy, exploration and maintenance metabolism under high food availability

Does metabolism constrain bird and mammal ranges and predict shifts in response to climate change?

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