Basking improves but winter warming worsens overwinter survival in the linden bug.

The present study investigates the effects of rare winter basking behavior (observed in wild populations of the Linden bug, Pyrrhocoris apterus) and the effects of winter warming (predicted by climate models) on overwinter survival and physiology of P. apterus. The insects were exposed to scenarios simulating basking and winter warming in the laboratory. Part of the insects were exposed to real winters under semi-natural conditions in the field for comparison. The results show a clear positive effect of winter basking, implying that basking behavior is critical for overwinter survival in P. apterus. In contrast, winter warming was found to have a strong negative effect on overwinter survival, potentially representing a threat to central European populations of P. apterus. Physiological parameters (mass, water content, SCP, energy reserves) measured in this study cannot fully explain all the results. Further study is needed to better understand the mechanisms behind the positive effects of winter basking and the negative effects of winter warming on overwintering P. apterus.

How turtles keep their cool: Seasonal and diel basking patterns in a tropical turtle.

Behavioural thermoregulation by ectotherms is an important mechanism for maintaining body temperatures to optimise physiological performance. Experimental studies suggest that nocturnal basking by Krefft's river turtles (Emydura macquarii krefftii) in the tropics may allow them to avoid high water temperatures, however, this hypothesis has yet to be tested in the field. In this study, we examined the influence of environmental temperature on seasonal and diel patterns of basking in E. m. krefftii in tropical north Queensland, Australia. Wildlife cameras were used to document turtle basking events for seven consecutive days and nights for each month over a year (April 2020-March 2021). Air and water temperatures were recorded simultaneously using temperature loggers. We used a negative binomial mixed effects model to compare mean basking durations (min) occurring among four environmental temperature categories based on population thermal preference (26 °C): 1) air temperature above and water temperature below preferred temperature; 2) air temperature below and water temperature above preferred temperature; 3) air and water temperatures both above preferred temperature; and 4) air and water temperatures both below preferred temperature. Basking behaviour was influenced significantly by the relationship between air and water temperature. During the day, turtles spent significantly less time basking when both air and water temperatures were above their preferred temperatures. Conversely, at night, turtles spent significantly more time basking when water temperatures were warm and air temperatures were cool relative to their preferred temperature. This study adds to the growing body of work indicating pronounced heat avoidance as a thermoregulatory strategy among tropical reptile populations.

How seasonality influences the thermal biology of lizards with different thermoregulatory strategies: a meta-analysis.

Ectotherms that maintain thermal balance in the face of varying climates should be able to colonise a wide range of habitats. In lizards, thermoregulation usually appears as a variety of behaviours that buffer external influences over physiology. Basking species rely on solar radiation to raise body temperatures and usually show high thermoregulatory precision. By contrast, species that do not bask are often constrained by climatic conditions in their habitats, thus having lower thermoregulatory precision. While much focus has been given to the effects of mean habitat temperatures, relatively less is known about how seasonality affects the thermal biology of lizards on a macroecological scale. Considering the current climate crisis, assessing how lizards cope with temporal variations in environmental temperature is essential to understand better how these organisms will fare under climate change. Activity body temperatures (Tb ) represent the internal temperature of an animal measured in nature during its active period (i.e. realised thermal niche), and preferred body temperatures (Tpref ) are those selected by an animal in a laboratory thermal gradient that lacks thermoregulatory costs (i.e. fundamental thermal niche). Both traits form the bulk of thermal ecology research and are often studied in the context of seasonality. In this study, we used a meta-analysis to test how environmental temperature seasonality influences the seasonal variation in the Tb and Tpref of lizards that differ in thermoregulatory strategy (basking versus non-basking). Based on 333 effect sizes from 137 species, we found that Tb varied over a greater magnitude than Tpref across seasons. Variations in Tb were not influenced by environmental temperature seasonality; however, body size and thermoregulatory strategy mediated Tb responses. Specifically, larger species were subjected to greater seasonal variations in Tb , and basking species endured greater seasonal variations in Tb compared to non-basking species. On the other hand, the seasonal variation in Tpref increased with environmental temperature seasonality regardless of body size. Thermoregulatory strategy also influenced Tpref , suggesting that behaviour has an important role in mediating Tpref responses to seasonal variations in the thermal landscape. After controlling for phylogenetic effects, we showed that Tb and Tpref varied significantly across lizard families. Taken together, our results support the notion that the relationship between thermal biology responses and climatic parameters can be taxon and trait dependent. Our results also showcase the importance of considering ecological and behavioural aspects in macroecological studies. We further highlight current systematic, geographical, and knowledge gaps in thermal ecology research. Our work should benefit those who aim to understand more fully how seasonality shapes thermal biology in lizards, ultimately contributing to the goal of elucidating the evolution of temperature-sensitive traits in ectotherms.

Common lizard microhabitat selection varies by sex, parity mode, and colouration.

BACKGROUND: Animals select and interact with their environment in various ways, including to ensure their physiology is at its optimal capacity, access to prey is possible, and predators can be avoided. Often conflicting, the balance of choices made may vary depending on an individual's life-history and condition. The common lizard (Zootoca vivipara) has egg-laying and live-bearing lineages and displays a variety of dorsal patterns and colouration. How colouration and reproductive mode affect habitat selection decisions on the landscape is not known. In this study, we first tested if co-occurring male and female viviparous and oviparous common lizards differ in their microhabitat selection. Second, we tested if the dorsal colouration of an individual lizard matched its basking site choice within the microhabitat where it was encountered, which could be related to camouflage and crypsis. RESULTS: We found that site use differed from the habitat otherwise available, suggesting lizards actively choose the composition and structure of their microhabitat. Females were found in areas with more wood and less bare ground compared to males; we speculate that this may be for better camouflage and reducing predation risk during pregnancy, when females are less mobile. Microhabitat use also differed by parity mode: viviparous lizards were found in areas with more density of flowering plants, while oviparous lizards were found in areas that were wetter and had more moss. This may relate to differing habitat preferences of viviparous vs. oviparous for clutch lay sites. We found that an individual's dorsal colouration matched that of the substrate of its basking site. This could indicate that individuals may choose their basking site to optimise camouflage within microhabitat. Further, all individuals were found basking in areas close to cover, which we expect could be used to escape predation. CONCLUSIONS: Our study suggests that common lizards may actively choose their microhabitat and basking site, balancing physiological requirements, escape response and camouflage as a tactic for predator avoidance. This varies for parity modes, sexes, and dorsal colourations, suggesting that individual optimisation strategies are influenced by inter-individual variation within populations as well as determined by evolutionary differences associated with life history.

Hide or die when the winds bring wings: predator avoidance by activity shift in a mountain snake.

BACKGROUND: Understanding predator-prey relationships is fundamental in many areas of ecology and conservation. In reptiles, basking time often increases the risk of predation and one way to minimise this risk is to reduce activity time and to stay within a refuge. However, this implies costs of lost opportunities for foraging, reproduction, and thermoregulation. We aimed to determine the main potential and observed predators of Vipera graeca, to infer predation pressure by estimating the incidence and the body length and sex distribution of predation events based on body injuries, and to assess whether and how the activity of V. graeca individuals is modified by predation pressure. RESULTS: We observed n = 12 raptor bird species foraging at the study sites, of which Circaetus gallicus, Falco tinnunculus and Corvus cornix were directly observed as predators of V. graeca. We found injuries and wounds on 12.5% of the studied individuals (n = 319). The occurrence of injuries was significantly positively influenced by the body length of vipers, and was more frequent on females than on males, while the interaction of length and sex showed a significant negative effect. The temporal overlap between predator and viper activity was much greater for the vipers' potential activity than their realised activity. Vipers showed a temporal shift in their bimodal daily activity pattern as they were active earlier in the morning and later in the afternoon than could be expected based on the thermal conditions. CONCLUSION: The time spent being active on the surface has costs to snakes: predation-related injuries increased in frequency with length, were more frequent in females than in males and occurred in shorter length for males than for females. Our results suggest that vipers do not fully exploit the thermally optimal time window available to them, likely because they shift their activity to periods with fewer avian predators.

Dissimilar use of an external heat source for thermoregulation by shrews from different geographic regions.

Ambient temperature has a substantial influence on the thermoregulation costs of small mammals due to their high surface-to-volume ratio. Shrews are among the smallest of mammals and have adopted different behavioral and physiological strategies to deal with cold temperatures. In this study, we assessed the use of an external heat source in the thermoregulatory strategy of two Crocidurinae species, Crocidura russula and C. suaveolens, and one Soricinae species, Sorex araneus. Crocidura russula inhabits western Europe and is better adapted to a Mediterranean climate; C. suaveolens inhabits central Europe; and S. araneus inhabits northern Europe and is better adapted to a Palearctic climate. We predicted that C. russula (most southern species) would spend larger amounts of time using an external heat source because it is the most cold-sensitive species, while S. araneus (most northern species) would spend less time using an external heat source or not respond to it. Shrews were experimentally tested in captivity inside a terrarium where they had access to a heat rock, which could be turned off (cold) or on (heated), depending on treatment. Our results confirmed our initial prediction: C. russula was the species that spent significantly more time on the heated rock, followed by C. suaveolens. Only a quarter of S. araneus individuals spent large amounts of time on the heat rock, which suggests this thermoregulation strategy is not generally adopted by this species, but may be rather associated with some individual personalities. We also analyzed the influence of the heat rock on rewarming from heterothermy, but heterothermy was not different between rock treatments. Overall, our results show that shrew species use external heat sources for thermoregulation according to their sensitivity to cold.

Identity Selection and the Social Construction of Birthdays.

We argue that rather than being a wholly random event, birthdays are sometimes selected by parents. We further argue that such effects have changed over time and are the result of important psychological processes. Long ago, U.S. American parents greatly overclaimed holidays as their children's birthdays. These effects were larger for more important holidays, and they grew smaller as births moved to hospitals and became officially documented. These effects were exaggerated for ethnic groups that deeply valued specific holidays. Parents also overclaimed well-liked calendar days and avoided disliked calendar days as their children's birthdays. However, after birthday selection effects virtually disappeared in the 1950s and 1960s, they reappeared after the emergence of labor induction and planned cesarean birth. For example, there are many fewer modern U.S. births than would be expected on Christmas Day. In addition, modern parents appear to use birth medicalization to avoid undesirable birthdays (Friday the 13th). We argue that basking in reflect glory, ethnic identity processes, and superstitions such as magical thinking all play a role in birthday selection effects. Discussion focuses on the power of social identity in day-to-day judgment and decision-making.

Leech removal is not the primary driver of basking behavior in a freshwater turtle.

Leaving the water to bask (usually in the sun) is a common behavior for many freshwater turtles, with some species also engaging in "nocturnal basking." Ectoparasite removal is an obvious hypothesis to explain nocturnal basking and has also been proposed as a key driver of diurnal basking. However, the efficacy of basking, day or night, to remove leeches has not been experimentally tested. Therefore, we examined the number of leeches that were removed from Krefft's river turtles (Emydura macquarii krefftii) after experimentally making turtles bask at a range of times of day, durations, and temperatures. Turtles had high initial leech loads, with a mean of 32.1 leeches per turtle. Diurnal basking under a heat lamp for 3 hr at ~28°C significantly reduced numbers of leeches relative to controls. In diurnal trials, 90.9% of turtles lost leeches (mean loss of 7.1 leeches per turtle), whereas basking for 30 min under the same conditions was not effective (no turtles lost leeches, and all turtles were still visibly wet). Similarly, "nocturnal basking" at ~23°C for 3 hr was not effective at removing leeches. Only 18% of turtles lost leeches (one turtle lost one leech and another lost four leeches). Diurnal basking outdoors under direct sunlight for 20 min (mean temp = 34.5°C) resulted in a small reduction in leeches, with 50% of turtles losing leeches and an average loss of 0.7 leeches per turtle. These results indicate basking can remove leeches if temperatures are high or basking durations are long. However, it was only effective at unusually long basking durations in this system. Our data showed even the 20-min period was longer than 70.1% of natural diurnal basking events, many of which took place at cooler temperatures. Therefore, leech removal does not appear to be the purpose of the majority of basking events.

Serendipitous re-sighting of a basking shark Cetorhinus maximus reveals inter-annual connectivity between American and European coastal hotspots.

Transatlantic stock mixing in basking sharks Cetorhinus maximus is supported by low genetic diversity in populations throughout the Atlantic Ocean. However, despite significant focus on the species' movements; >1500 individual sharks marked for recapture and >150 individuals equipped with remote tracking tags, only a single record of transatlantic movment has been previously recorded. Within this context, the seredipitous re-sighting of a female basking shark fitted with a satellite transmitter at Malin Head, Ireland 993 days later at Cape Cod, USA is noteworthy.

Importance of Body Stance in Fog Droplet Collection by the Namib Desert Beetle.

The fog-basking behavior of the Onymacris unguicularis, a beetle species living in the coastal regions of the Namibian desert, has recently caught the attention of the engineering community, as suggesting a viable biomimetic approach to address the problem of harvesting water in arid regions of the globe. Previous research has focused on observation and analysis of the beetle's elytron properties and how these affect fog-collection rates. The head stance taken by the Onymacris unguicularis when fog basking is well documented. However, how this stance affects droplet collection has not been studied up to now. The present paper addresses this problem from a computational fluid dynamics perspective, where three-dimensional numerical simulations are used to characterize the fog flow properties around a simplified geometry mimicking the beetle's body. The simulations employ two-way coupling between the gas flow and the dispersed fog phase to account for feedback effects of fog droplets on the carrier fluid (air), and assume that droplets are captured after hitting the elytron surface. The study considers several combinations of free-stream velocity and droplet volume fraction. The analysis reveals that there is a range of head-stance angles, corresponding to an inclination of the beetle between 35 deg and 45 deg with respect to the horizon, that maximizes water collection on the beetle's back, in qualitative agreement with observations in nature and laboratory experiments. A rationale is proposed to explain this phenomenon, finding that the specific head stance corresponds to the maximum residence time of fluid particles above the beetle's elytron surface. This, in turn, designates the maximum likelihood for water droplets to be captured in the boundary layer developing over the beetle and subsequently hit the surface where they get captured. The results reveal the importance of the fluid flow pattern around the beetle's body in addition to the microphysical properties of the elytron when reliable predictions of the water droplet collection efficiency are sought.

The crocodylian skull and osteoderms: A functional exaptation to ectothermy?

The crocodylians are ectothermic semi-aquatic vertebrates which are assessed to have evolved from endothermic terrestrial forms during the Mesozoic. Such a physiological transition should have involved modifications in their cardio-vascular system allowing to increase the heat transfers with the surrounding environment by growing a peripheral vascularization which would be mainly located in the dermal skeleton: the dermatocranium and the osteoderms. In order to assess the implication of these anatomical regions in thermal exchanges, we have recorded the temperature above a set of representative skin areas in order to draw comparisons between the skull, the osteoderms, and the rest of the body parts which present either none or residual dermal ossification. We computed the data after the specimens were successively laid in different stereotyped environmental conditions which involved significant variations in the environmental temperature. Our results show that the osteoderms collect the external heat during the basking periods as they become significantly warmer than the surrounding skin; they further release the heat into the core of the organism as they turn out to be colder than the surrounding skin after a significant cooling period. In disregard of the environmental temperature variations, the skull table (which encloses the braincase) remains warmer than the rest of the cranial regions and shows less temperature variations than the osteoderms; a result which has lead us to think that the braincase temperature is monitored and controlled by a thermoregulatory system. Therefore, as hypothesized by previous authors regarding the ectothermic diapsids, we assume that the crocodylian skull possesses shunting blood pathways which tend to maintain both the braincase and the main sensory organs at the nearest to the optimal physiological temperature depending on the external temperature variations. Concerning the skin vascularization, the study of an albino Alligator mississippiensis specimen permitted to observe the repartition of the superficial blood vessels by transparency through the skin. We thus testify that the skin which covers either the skull or the osteoderms is more vascularized than the skin which does not present any subjacent dermal ossification. We consequently deduce that the significant contrast in the thermal behavior between the dermal skeleton and the rest of the body is indeed correlated with a difference in the relative degree of skin vascularization. This last assessment confirms that the development of the dermal skeleton should have played a functional role in the crocodylian transition from endothermy to ectothermy through the set-up of a peripheral vessel network.

Sun-basking fish benefit from body temperatures that are higher than ambient water.

In terrestrial environments, cold-blooded animals can attain higher body temperatures by sun basking, and thereby potentially benefit from broader niches, improved performance and higher fitness. The higher heat capacity and thermal conductivity of water compared with air have been universally assumed to render heat gain from sun basking impossible for aquatic ectotherms, such that their opportunities to behaviourally regulate body temperature are largely limited to choosing warmer or colder habitats. Here we challenge this paradigm. Using physical models we first show that submerged objects exposed to natural sunlight attain temperatures in excess of ambient water. We next demonstrate that free-ranging carp (Cyprinus carpio) can increase their body temperature during aquatic sun basking close to the surface. The temperature excess gained by basking was larger in dark than in pale individuals, increased with behavioural boldness, and was associated with faster growth. Overall, our results establish aquatic sun basking as a novel ecologically significant mechanism for thermoregulation in fish. The discovery of this previously overlooked process has practical implications for aquaculture, offers alternative explanations for behavioural and phenotypic adaptations, will spur future research in fish ecology, and calls for modifications of models concerning climate change impacts on biodiversity in marine and freshwater environments.

Characterization of large basking shark Cetorhinus maximus aggregations in the western North Atlantic Ocean.

Cetorhinus maximus aggregations recorded during extensive aerial survey efforts off the north-eastern United States between 1980 and 2013 included aggregations centring on sightings with group sizes of at least 30 individuals. These aggregations occurred in summer and autumn months and included aggregation sizes of up to 1398 individuals, the largest aggregation ever reported for this species. The aggregations were associated with sea surface temperatures of 13-24° C and chlorophyll-a concentrations of 0·4-2·6 mg m-3 and during one aggregation, a high abundance of zooplankton prey was present. Photogrammetric tools allowed for the estimation of total body lengths ranging between 4 and 8 m. Characterization of these events provides new insight into the potential biological function of large aggregations in this species.

Interspecies differences in plasma concentrations of 25-hydroxyvitamin D3 and dermal Vitamin D synthesis of kiwi (Apteryx mantelli), tuatara (Sphenodon punctatus), and New Zealand sea lions (Phocarctos hookeri).

Vitamin D plays a central role in calcium homeostasis of most vertebrates, and is obtained in different species through diet, dermal synthesis, or a combination of both. The aim of this study was to determine the predominant routes of Vitamin D synthesis in three disparate species, brown kiwi (Apteryx mantelli), tuatara (Sphenodon punctatus), and New Zealand sea lions (Phocarctos hookeri). We surveyed plasma concentrations of 25-hydroxyvitamin D2 and D3, analysed environmental conditions and life history factors, and determined the ability of skin samples to synthesise Vitamin D3 on exposure to ultraviolet-B radiation. There was variation in the plasma/serum 25-hydroxyvitamin D3 concentrations between and within the species studied, with wild kiwi having the lowest concentrations and NZ sea lions the highest. Kiwi skin produced small but measurable amounts of Vitamin D3, while tuatara skin produced Vitamin D3 concentrations higher than that of kiwi. New Zealand sea lion skin produced the highest amount of Vitamin D3 and differed from the other two species in this study in that Vitamin D3 was present in skin before UV-B exposure. The results from this study show that all three species studied retained the ability to use both dietary and dermal sources of Vitamin D, although there was interspecies variation in the magnitude of dermal synthesis. Comparisons between these species show that there are differences in their Vitamin D pathways, but suggest that there are more factors contributing to these pathways than might be expected solely from life history characteristics.

Thermal acclimation in American alligators: Effects of temperature regime on growth rate, mitochondrial function, and membrane composition.

We investigated the ability of juvenile American alligators (Alligator mississippiensis) to acclimate to temperature with respect to growth rate. We hypothesized that alligators would acclimate to cold temperature by increasing the metabolic capacity of skeletal muscles and the heart. Additionally, we hypothesized that lipid membranes in the thigh muscle and liver would respond to low temperature, either to maintain fluidity (via increased unsaturation) or to maintain enzyme reaction rates (via increased docosahexaenoic acid). Alligators were assigned to one of 3 temperature regimes beginning at 9 mo of age: constant warm (30°C), constant cold (20°C), and daily cycling for 12h at each temperature. Growth rate over the following 7 mo was highest in the cycling group, which we suggest occurred via high digestive function or feeding activity during warm periods and energy-saving during cold periods. The warm group also grew faster than the cold group. Heart and liver masses were proportional to body mass, while kidney was proportionately larger in the cold group compared to the warm animals. Whole-animal metabolic rate was higher in the warm and cycling groups compared to the cold group - even when controlling for body mass - when assayed at 30°C, but not at 20°C. Mitochondrial oxidative phosphorylation capacity in permeabilized fibers of thigh muscle and heart did not differ among treatments. Membrane fatty acid composition of the brain was largely unaffected by temperature treatment, but adjustments were made in the phospholipid headgroup composition that are consistent with homeoviscous adaptation. Thigh muscle cell membranes had elevated polyunsaturated fatty acids in the cold group relative to the cycling group, but this was not the case for thigh muscle mitochondrial membranes. Liver mitochondria from cold alligators had elevated docosahexaenoic acid, which might be important for maintenance of reaction rates of membrane-bound enzymes.

Spontaneous magnetic alignment behaviour in free-living lizards.

Several species of vertebrates exhibit spontaneous longitudinal body axis alignment relative to the Earth's magnetic field (i.e., magnetic alignment) while they are performing different behavioural tasks. Since magnetoreception is still not fully understood, studying magnetic alignment provides evidence for magnetoreception and broadens current knowledge of magnetic sense in animals. Furthermore, magnetic alignment widens the roles of magnetic sensitivity in animals and may contribute to shed new light on magnetoreception. In this context, spontaneous alignment in two species of lacertid lizards (Podarcis muralis and Podarcis lilfordi) during basking periods was monitored. Alignments in 255 P. muralis and 456 P. lilfordi were measured over a 5-year period. The possible influence of the sun's position (i.e., altitude and azimuth) and geomagnetic field values corresponding to the moment in which a particular lizard was observed on lizards' body axis orientation was evaluated. Both species exhibited a highly significant bimodal orientation along the north-northeast and south-southwest magnetic axis. The evidence from this study suggests that free-living lacertid lizards exhibit magnetic alignment behaviour, since their body alignments cannot be explained by an effect of the sun's position. On the contrary, lizard orientations were significantly correlated with geomagnetic field values at the time of each observation. We suggest that this behaviour might provide lizards with a constant directional reference while they are sun basking. This directional reference might improve their mental map of space to accomplish efficient escape behaviour. This study is the first to provide spontaneous magnetic alignment behaviour in free-living reptiles.

The role of basking in the development of endothermy and torpor in a marsupial.

Marsupials have a slow rate of development and this allows a detailed examination of thermoregulatory developmental changes and stages. We quantified the cooling rates of marsupial dunnarts (Sminthopsis crassicaudata) at 40-56 days (d) old, and torpor and basking behaviour in animals given the option to bask in four age groups from 60 to 150 d. The development of thermoregulation was a continuum, but was characterised by three major thermoregulatory stages: (1) at 40 d, animals were unable to maintain a constant high body temperature during short-term cold exposure; (2) at 60 d, animals could maintain a high T b for the first part of the night at an ambient temperature of 15.0 ± 0.7 °C; later in the night, they entered an apparent torpor bout but could only rewarm passively when basking under a heat lamp; (3) from ~90 d, they expressed prolonged torpor bouts and were able to rewarm endogenously. Young newly weaned 60 d animals were able to avoid hypothermia by basking. In this case, basking was not an optional behavioural method of reducing the cost of rewarming from torpor, but was essential for thermoregulation independent of the nest temperature. Results from our study suggest that basking is a crucial behavioural trait that permits young marsupials and perhaps other juvenile altricial mammals to overcome the developmental stage between poikilothermy early in development and full endothermy later in life.

Thermal variability alters the impact of climate warming on consumer-resource systems.

Thermal variation through space and time are prominent features of ecosystems that influence processes at multiple levels of biological organization. Yet, it remains unclear how populations embedded within biological communities will respond to climate warming in thermally variable environments, particularly as climate change alters existing patterns of thermal spatial and temporal variability. As environmental temperatures increase above historical ranges, organisms may increasingly rely on extreme habitats to effectively thermoregulate. Such locations desirable in their thermal attributes (e.g., thermal refugia) are often suboptimal for resource acquisition (e.g., underground tunnels). Thus, via the expected increase in both mean temperatures and diel thermal variation, climate warming may heighten the trade-off for consumers between behaviors maximizing thermal performance and those maximizing resource acquisition. Here, we integrate behavioral, physiological, and trophic ecology to provide a general framework for understanding how temporal thermal variation, mediated by access to a thermal refugium, alters the response of consumer-resource systems to warming. We use this framework to predict how temporal variation and access to thermal refugia affect the persistence of consumers and resources during climate warming, how the quality of thermal refugia impact consumer-resource systems, and how consumer-resource systems with fast vs. slow ecological dynamics respond to warming. Our results show that the spatial thermal variability provided by refugia can elevate consumer biomass at warmer temperatures despite reducing the fraction of time consumers spend foraging, that temporal variability detrimentally impacts consumers at high environmental temperatures, and that consumer-resource systems with fast ecological dynamics are most vulnerable to climate warming. Thus, incorporating both estimates of thermal variability and species interactions may be necessary to accurately predict how populations respond to warming.

The functional requirements of mammalian hair: a compromise between crypsis and thermoregulation?

Mammalian fur often shows agouti banding with a proximal dark band near the skin and a lighter distal band. We examined the function of both bands in relation to camouflage, thermal properties of pelts, and thermal energetics of dunnarts (Sminthopsis crassicaudata), which are known to use torpor and basking. Although the distal band of dunnart fur darkened with increasing latitude, which is important for camouflage, it did not affect the thermal properties and the length of the dark band and total hair length were not correlated. In contrast, the length of the proximal dark band of preserved pelts exposed to sunlight was positively correlated (r (2) = 0.59) with the temperature underneath the pelt (T pelt). All dunnarts offered radiant heat basked by exposing the dark band of the hair during both rest and torpor. Basking dunnarts with longer dark bands had lower resting metabolism (r (2) = 0.69), warmed faster from torpor (r (2) = 0.77), required less energy to do so (r (2) = 0.32), and reached a higher subcutaneous temperature (T sub) at the end of rewarming (r (2) = 0.75). We provide the first experimental evidence on the possible dual function of the color banding of mammalian fur. The distal colored band appears to be important for camouflage, whereas the length of the dark proximal hair band facilitates heat gain for energy conservation and allows animals to rewarm quickly and economically from torpor.