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Abstract Within optimal foraging theory animals should maximize their net energy gain while minimizing energetic costs. Energetic expenditure in wild animals is therefore key to measure proxies of fitness. Accelerometers are an effective tool to study animal movement-based energetics, but retrieval of the device is usually required and often difficult. Accelerometers measure movement across three axes (x, y, and z) and can be calibrated to measures of oxygen consumption from captive animals, providing estimates of overall energy expenditure. Measuring energetic expenditures using a global positioning system (GPS) approach could provide an alternative method to study energetic ecology. This technique uses locomotor speeds across a range of slopes from successive GPS locations, which can be linked to the energy expenditure from captive individuals. We compared accelerometer and GPS methods of energetic expenditures in free-roaming brown bears (Ursus arctos) on the Kodiak Archipelago, Alaska, USA. We then applied the GPS method to examine how multiple factors influenced brown bear movement-based daily energetic expenditures (MDEE). We found that while the two energetic measurements differed (Wilcoxon signed rank test: V = 2116, p

Within optimal foraging theory animals should maximize their net energy gain while minimizing energetic costs. Energetic expenditure in wild animals is therefore key to measure proxies of fitness. Accelerometers are an effective tool to study animal movement-based energetics, but retrieval of the device is usually required and often difficult. Accelerometers measure movement across three axes (x, y, and z) and can be calibrated to measures of oxygen consumption from captive animals, providing estimates of overall energy expenditure. Measuring energetic expenditures using a global positioning system (GPS) approach could provide an alternative method to study energetic ecology. This technique uses locomotor speeds across a range of slopes from successive GPS locations, which can be linked to the energy expenditure from captive individuals. We compared accelerometer and GPS methods of energetic expenditures in free-roaming brown bears (Ursus arctos) on the Kodiak Archipelago, Alaska, USA. We then applied the GPS method to examine how multiple factors influenced brown bear movement-based daily energetic expenditures (MDEE). We found that while the two energetic measurements differed (Wilcoxon signed rank test: V = 2116, p < 0.001), they were positively correlated (r = 0.82, p < 0.001). The GPS method on average provided 1.6 times greater energy estimates than the accelerometer method. Brown bears had lower MDEE during periods of high food abundance, supporting optimal foraging theory. Reproductive status and age did not influence MDEE, however movement rates had a positive linear relationship. Energetic ecology is important for understanding drivers of animal movements. Data from GPS collars can provide useful information on energetic expenditures, but should be validated for the specific taxa, ecosystem, and GPS sampling rate used. Additionally, while movement-based estimates of energy expenditure can elucidate the mechanisms driving habitat use decisions, they may not fully reflect an animal's overall energy demands. Brown bear movement-based energetic expenditure was influenced by food abundance and movement rates, which highlighted the importance of access to prime foraging sites to enhance energetic efficiency. [ABSTRACT FROM AUTHOR]

Metabolic rate is a basic individual metric that extends beyond the individual to link the ecology of populations, communities, and ecosystems via its role as a central component of energy budgets. Metabolic rates are often measured indirectly by quantifying respiration under simplified, standard laboratory conditions. This approach limits the application of these measurements to a small range of conditions that commonly do not reflect natural field conditions. We measured metabolic rates of the squareback marsh crab Armases cinereum under field conditions. Previous work highlights that movement of individual A. cinereum, especially females, provides a potential spatial subsidy of energy, as individuals consume foods in salt marshes and then transfer the resulting energy to upland forest ecosystems. We show that metabolic rate increases with size for both males and females and that metabolic rates are influenced by temperature and by whether females are vitellogenic. The metabolic rates that we measured more closely approximate field metabolic rates than standard metabolic rates and demonstrate that individual crabs experience high energy expenditures, reducing the amount of energy that may be transferred as a subsidy between marsh and forest as a result of the daily movements of individual crabs. Our measurements are therefore also a key component for the construction of an energy budget for this species. [ABSTRACT FROM AUTHOR]

Research Highlight: Réveillon, T., Rota, T., Chauvet, É., Lecerf, A., & Sentis, A. (2022). Energetic mismatch induced by warming decreases leaf litter decomposition by aquatic detritivores. Journal of Animal Ecology, https://doi.org/10.1111/1365‐2656.13710. Global change holds complex consequences for Earth's ecosystems, with global warming simultaneously affecting multiple aspects including individual physiology, population dynamics and ecosystem processes. In a recent study on stream decomposition under global warming, Réveillon, et al. (2022) combined individual‐level laboratory assessments of metabolic rates and leaf‐litter ingestion with experimentally parameterized consumer‐resource models, designed to reveal how stream‐detritivore populations respond to combined impacts of warming and declining body size. Their findings of reduced energetic efficiency, weakened detritivore populations and reduced decomposition in warmed streams expand our understanding of how global change mechanistically links changes from the individual to the ecosystem level. [ABSTRACT FROM AUTHOR]

Aim: Understanding variation in offspring energy expenditure is important because energy is critical for growth and development. Weather may exert proximate effects on offspring energy expenditure, but in altricial species these might be masked by parental care and huddling with siblings. Such effects are particularly important to understand given changing global weather patterns, yet studies of wild offspring in the presence of parental care are lacking. Offspring energy expenditure may also vary among species due to evolved responses to environmental selection pressures, requiring studies at both proximate and ultimate levels. Location: USA, South Africa, Malaysia. Time period: 2016–2019. Major taxa studied: Songbirds. Methods: We used the doubly‐labelled water technique to estimate nestling daily energy expenditure of 54 songbird species across three continents. We used Bayesian phylogenetic mixed models to test proximate and evolutionary causes of variation in offspring energy expenditure while accounting for phylogeny and phylogenetic uncertainty. Results: Offspring energy expenditure increased with more rainfall and colder air temperatures, but decreased among offspring in broods with more siblings. Across species, nestling and adult mortality, but not growth rate, were positively associated with offspring energy use. Main conclusions: Weather had clear proximate effects on offspring energy expenditure and parents were either unable or unwilling to fully offset these effects. However, the decrease in offspring energy use when huddling with more siblings demonstrated a modulating effect of life history traits. For example, high nest predation rates favour reduced parental care and can force offspring to spend more energy coping with environmental conditions. Furthermore, reduced energy expenditure is thought to facilitate increased longevity, which is increasingly realized with lower extrinsic mortality rates, providing an explanation for the positive association between adult mortality and offspring energy expenditure. Ultimately, both proximate and evolutionary influences need to be considered to better understand causes of offspring energetics. [ABSTRACT FROM AUTHOR]

Concomitant to the decline of tropical corals caused by increasing global sea temperatures is the potential removal of barriers to species range expansions into subtropical and temperate habitats. In these habitats, species must tolerate lower annual mean temperature, wider annual temperature ranges and lower minimum temperatures. To understand ecophysiological traits that will impact geographical range boundaries, we monitored populations of five coral species within a marginal habitat and used a year of in situ measures to model thermal performance of vital host, symbiont and holobiont physiology. Metabolic responses to temperature revealed two acclimatization strategies: peak productivity occurring at annual midpoint temperatures (4–6°C lower than tropical counterparts), or at annual maxima. Modelled relationships between temperature and P:R were compared to a year of daily subtropical sea temperatures and revealed that the relatively short time spent at any one temperature, limited optimal performance of all strategies to approximately half the days of the year. Thus, while subtropical corals can adjust their physiology to persist through seasonal lows, seasonal variation seems to be the key factor limiting coral productivity. This constraint on rapid reef accretion within subtropical environments provides insight into the global distribution of future coral reefs and their ecosystem services. [ABSTRACT FROM AUTHOR]

Doubly labelled water (DLW) is routinely used to measure energy expenditure and water turnover in free‐ranging animals. Standard methods involve capture, blood sampling for baseline measurement, injection with isotopic tracers, captivity for an equilibration period, post‐dose blood sampling, release and subsequent recapture for final blood sampling. Single sampling methods that minimise disturbance by reducing capture and handling time have been developed and tested. Sampling faeces rather than blood could further reduce disturbance to study animals in a range of species and study systems. However, the extent to which estimates of metabolic rate derived from blood and faecal samples diverge has not been investigated.We compared isotopic enrichment in blood and faecal samples taken concurrently from captive Southern Pied Babblers Turdoides bicolor. Isotopic enrichment levels in faeces and in blood were used to calculate initial and final ratios of δ18O/δ2H for each individual. We then used these ratios to calculate daily energy expenditure (DEE) and directly compared measurements from blood samples with those from faecal samples within individuals. We found that faecal sampling resulted in estimates of DEE that agree with those based on blood sampling.Additionally, we field‐tested a faecal sampling protocol with a habituated population of babblers in the southern Kalahari Desert. During the field test, study animals were not captured or handled for either dosing or sampling. Field‐testing confirmed the practical feasibility of non‐invasive dosing and sampling techniques in free‐living animals, and we obtained measurements of DEE that we used to test an a priori prediction that DEE is inversely related to air temperature. Our data show decreasing DEE with increasing air temperature, a pattern consistent with studies testing similar predictions in birds using traditional DLW methods.We demonstrate that faecal samples can substitute for blood when measuring DEE using DLW and provide a method that will allow field‐based researchers to obtain sound physiological measurements while minimising handling and removal of study animals from their natural environments. A plain language summary is available for this article. Plain Language Summary [ABSTRACT FROM AUTHOR]

Species distribution models can be informative of the biodiversity impacts of changing environments at global, national, and regional scales, but are often constrained in their resolution to extents not relevant to individual, intensive ecological management programs. We constructed a high‐resolution topoclimatic model of spring and summer temperatures across a 152 km2 restoration area on the Swan Coastal Plain, Western Australia, and used it to project energetic expenditure and habitat suitability estimates for four major hymenopteran pollinators. For all species, the most heavily modified landscapes were the least suitable, but only for one species, Zapsilothynnus nigripes, was there evidence that the upper thermal tolerance threshold was exceeded broadly. However, at the higher environmental temperatures that we modeled, some species would need to forage up to 10 times their own body mass every hour to meet their energetic requirements. It seems unlikely that the nutritional requirements of most insect pollinators operating at these higher metabolic rates could be met in an impoverished restoration ecosystem, although resource availability remains to be quantified in these habitats. Hence, to increase the likelihood of restoration success by restoring insect pollination networks, nutritional resources may need to be increased during restoration. Accounting for the way that thermoenergetic requirements shape ecological interactions better positions management trajectories aimed at restoring and maintaining key insect pollinators in “novel” ecosystems. [ABSTRACT FROM AUTHOR]

Consumption is the basis of metabolic and trophic ecology and is used to assess an animal's trophic impact. The contribution of activity to an animal's energy budget is an important parameter when estimating consumption, yet activity is usually measured in captive animals. Developments in telemetry have allowed the energetic costs of activity to be measured for wild animals; however, wild activity is seldom incorporated into estimates of consumption rates. We calculated the consumption rate of a free-ranging marine predator (yellowtail kingfish, Seriola lalandi) by integrating the energetic cost of free-ranging activity into a bioenergetics model. Accelerometry transmitters were used in conjunction with laboratory respirometry trials to estimate kingfish active metabolic rate in the wild. These field-derived consumption rate estimates were compared with those estimated by two traditional bioenergetics methods. The first method derived routine swimming speed from fish morphology as an index of activity (a 'morphometric' method), and the second considered activity as a fixed proportion of standard metabolic rate (a 'physiological' method). The mean consumption rate for free-ranging kingfish measured by accelerometry was 152 J·g−1·day−1, which lay between the estimates from the morphometric method ( μ = 134 J·g−1·day−1) and the physiological method ( μ = 181 J·g−1·day−1). Incorporating field-derived activity values resulted in the smallest variance in log-normally distributed consumption rates ( σ = 0.31), compared with the morphometric ( σ = 0.57) and physiological ( σ = 0.78) methods. Incorporating field-derived activity into bioenergetics models probably provided more realistic estimates of consumption rate compared with the traditional methods, which may further our understanding of trophic interactions that underpin ecosystem-based fisheries management. The general methods used to estimate active metabolic rates of free-ranging fish could be extended to examine ecological energetics and trophic interactions across aquatic and terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Phenotypic selection is widely accepted as the primary cause of adaptive evolution in natural populations, but selection on complex functional properties linking physiology, behavior, and morphology has been rarely quantified. In ectotherms, correlational selection on thermal physiology, thermoregulatory behavior, and energy metabolism is of special interest because of their potential coadaptation. We quantified phenotypic selection on thermal sensitivity of locomotor performance (sprint speed), thermal preferences, and resting metabolic rate in captive populations of an ectothermic vertebrate, the common lizard, Zootoca vivipara. No correlational selection between thermal sensitivity of performance, thermoregulatory behavior, and energy metabolism was found. A combination of high body mass and resting metabolic rate was positively correlated with survival and negatively correlated with fecundity. Thus, different mechanisms underlie selection on metabolism in lizards with small body mass than in lizards with high body mass. In addition, lizards that selected the near average preferred body temperature grew faster that their congeners. This is one of the few studies that quantifies significant correlational selection on a proxy of energy expenditure and stabilizing selection on thermoregulatory behavior. [ABSTRACT FROM AUTHOR]

Metabolic rate is a positive function of body weight, a rule valid for most organisms and the basis of several theories of metabolic ecology. For adult insects, however, the diversity of relationships between body mass and respiration remains unexplained. The aim of this study is to relate the respiratory metabolism of a parasitoid with body weight and foraging activity. We compared the metabolic rate of groups of starving and host-fed females of the parasitoid Eupelmus vuilleti recorded with respirometry for 7 days, corresponding to the mean lifetime of starving females and over half of the lifetime of foraging females. The dynamics of carbohydrate, lipid and protein in the body of foraging females were quantified with biochemical techniques. Body mass and all body nutrients declined sharply from the first day onwards. By contrast, the CO 2 produced and the O 2 consumed increased steadily. Starving females showed the opposite trend, identifying foraging as the reason for the respiration increase of feeding females. Two complementary physiological processes explain the unexpected relationship between increasing metabolic rate and declining body weight. First, host hemolymph is a highly unbalanced food, and the excess nutrients (protein and carbohydrate) need to be voided, partially through excretion and partially through respiration. Second, a foraging young female produces eggs at an increasing rate during the first half of its lifetime, a process that also increases respiration. We posit that the time-varying metabolic rate contributions of the feeding and reproductive processes supplements the contribution of the structural mass and lead to the observed trend. We extend our explanations to other insect groups and discuss the potential for unification using Dynamic Energy Budget theory. [ABSTRACT FROM AUTHOR]

In near future it is essential for human society to switch its primary energy use from finite sources to renewable ones. Ethanol has been claimed to be a potential candidate to replace oil use to great extent. This study illustrates that ethanol production has the potential to rely on organic agriculture and thereby to reduce reliance on fossil fuels. Case studies were carried out by examining three farms (2 conventional, 1 organic) in Austria who are mainly producing sugar beet. We found that organic sugar beet production provided an overall energy return on investment (EROI) of 11.3 whereas the conventional farming practice showed an EROI of 14.1 and 15, respectively. Our study indicates that organic sugar beet production shows potential to substitute conventional industrial sugar beet production to provide inputs to ethanol production. By using organically produced sugar beets as inputs to the ethanol production, fossil fuels can perhaps be avoided to a large extent in the production process, thus, it may be possible to mitigate some of the environmental impacts associated with ethanol production. Larger studies are however needed to better visualise such results. [ABSTRACT FROM AUTHOR]

This is the first of two numbered papers for this Special Issue dealing with the ecological basis of environmentalism. The second follows, in a subsequent issue if not here. Patten (2013) gives a short preview of both papers. Problems of environmentalism—environmental protection, conservation, and preservation—are now widely appreciated as important to human enterprise and destiny. Called to attention by advances in descriptive empirical ecology, the new problems are too complex for this same ecology to solve without further expansion of basic knowledge. To understand how nature works two kinds of science are needed, one empirical, describing what is immediate and tangible, the other theoretical, developing first-principles understanding of what is indirect and intangible. Development of a complex systems theory based ecology is hindered by over-commitment of attention and resources to applied environmentalism. This may in its inadequacy run counter to how nature works, which could be detrimental to both humanity and nature. It is important to get the science right. As background for a revisionary hypothesis presented in Part II, five elements of basic ecology and five of applied environmentalism are here reviewed. The basic topics are ecological energetics, linear vs. nonlinear dynamics, steady vs. non-steady states, epistemic mediation, and indirect effects. The environmental topics are overpopulation, biodiversity, invasive species, sustainability, and global change. [ABSTRACT FROM AUTHOR]

Thermal stress affects organism performance differently depending on the ambient temperature to which they are acclimatized, which varies along latitudinal gradients. This study investigated whether differences in physiological responses to temperature are consistent with regional differences in temperature regimes for the stony coral Oculina patagonica. To resolve this question, we experimentally assessed how colonies originating from four different locations characterized by >3 °C variation in mean maximum annual temperature responded to warming from 20 to 32 °C. We assessed plasticity in symbiont identity, density, and photosynthetic properties, together with changes in host tissue biomass. Results show that, without changes in the type of symbiont hosted by coral colonies, O. patagonica has limited capacity to acclimatize to future warming. We found little evidence of variation in overall thermal tolerance, or in thermal optima, in response to spatial variation in ambient temperature. Given that the invader O. patagonica is a relatively new member of the Mediterranean coral fauna, our results also suggest that coral populations may need to remain isolated for a long period of time for thermal adaptation to potentially take place. Our study indicates that for O. patagonica, mortality associated with thermal stress manifests primarily through tissue breakdown under moderate but prolonged warming (which does not impair symbiont photosynthesis and, therefore, does not lead to bleaching). Consequently, projected global warming is likely to cause repeat incidents of partial and whole colony mortality and might drive a gradual range contraction of Mediterranean corals. [ABSTRACT FROM AUTHOR]

Abstract: Few green roof studies cover intensive and tropical types and specific canopy microclimate. We examined the ecological energetics of a sky woodland in humid-tropical Hong Kong. Environmental sensors monitored the microclimatic and soil parameters for 14 months. Key biophysical variables of transpiration, wind, light, and through-canopy energy flux are modeled to investigate seasonal and weather effects. The woodland forms a cloistered subcanopy environment with rather stable microclimate. Transpiration and latent heat loss are enhanced by solar radiation and low relative humidity, but less by wind. On sunny days, about 20% of incident solar radiation can reach the soil surface. The canopy reflected more near-infrared radiation (NIR) than photosynthetically active radiation (PAR), highlighting a hitherto neglected passive-cooling mechanism. The highest transpiration rate occurs in autumn rather than summer due to dry-mild weather. The woodland canopy could reduce 300Wm−2 energy flux into the substrate. The canopy warmed by solar energy transmits heat to subcanopy air. Latent and sensible heat loss in the subcanopy domain is suppressed, thus dampening the passive-cooling effect. The capability of the tropical intensive green roof to reduce temperature is relatively inefficient comparing with temperate region counterparts. The findings could inform design and choice of green roofs. [Copyright &y& Elsevier]

Diving endotherms inhabiting polar regions face potentially high thermoregulatory costs. Unless properly insulated, these animals will lose vast amounts of heat when diving in cold water, which has to be balanced by heat production. Heat generated as a by-product of digestion (heat increment of feeding, HIF) or from exercising muscles might be important in malntaining thermal balance under such conditions, as it would reduce the need for shivering thermogenesis. Recording the rate of oxygen consumption (VOJ, respiratory exchange ratio (RER), and stomach temperature, we studied the magnitude and duration of HIF in seven double-crested cormorants (Phalacrocorax auritus) following the voluntary ingestion of a single herring (Clupea pallasi) while birds rested in air. Conducting trials at thermoneutral (21.1i0.2"C) and sub-thermoneutral temperatures (5.5+0.7'C), we investigated the potential of HIF for thermal substitution. After the ingestion of a 100 g herring at thermoneutral conditions, VO, was elevated for an average of 328S2.8 min, during which time birds consumed 2697S2.94 ml02 in excess of the resting rate. At sub-thermoneutral conditions, duration (2286 min) and magnitude (1391S2.71 ml 02) of \io2 elevation were significantly reduced. This indicates that cormorants are able to use the heat generated as by-product of digestion to substitute for regulatory thermogenesis, if heat loss is sufficiently high. Altering meal size during sub-thermoneutral trials, we also found that HIF in cormorants was significantly greater after larger food intake. Based on these experimental results, a simple calculation suggests that substitution from HIF might reduce the daily thermoregulatory costs of double-crested cormorants wintering in coastal British Columbia by -38%. Magnitude of HIF and its potential for thermal substitution should be integrated into bioenergetic models to avoid overestimating energy expenditure in these top predators. [ABSTRACT FROM AUTHOR]

Current global change policy debate reverberates around the polarized extremes of civilization-level cooperation through treaties as a mitigation tactic, on the one hand, and a wait-and-see approach that may lead to a climatic tragedy of the commons, on the other. Meanwhile, energy technology research is rapidly generating a perception that it will be possible to tune the earth system via carbon sequestration and other types of biogeochemical engineering. The consequences of this potential for planetary management, based on provincial self-interest, include the transition of the earth sciences into a security industry involving proprietary scientific knowledge bases of biogeochemical cycling and the evolution of a climate-design brokerage dominated by military/industrial interests.As the dominant political powers perceive the potential for planetary engineering and consider implementation, the global economy will adjust to exploit new opportunities, perceptions of which will be determined by the quality of system simulations. The growth of a viable international climate-design community will profoundly influence the trajectory of the earth system by providing either the illusion or the reality of predictability. Although this process will be chaotic at first, the probability of stabilization will ultimately be enhanced because the vast resources of the military/industrial sector will become involved. These concepts are disturbingly familiar in that they acknowledge the pervasion of competition and conflict in human technological affairs. However, they are consistent with approaches used in thermodynamics, ecological energetics, behavioral evolution, economics, and interdisciplinary climate science to describe collectively the evolution of the earth system.This paper argues that the perception that the climate can be regulated inexpensively will create an economic driving force for international cartel-style management of the total earth system. That is, the earth system may well become syndicated by those with the resources to effect large-scale management. [Copyright &y& Elsevier]

Because of their small size and expensive mode of flight, hummingbirds display some of the highest known mass-specific rates of aerobic metabolism among vertebrates. High enzymatic flux capacities through pathways of carbohydrate and long-chain fatty acid oxidation indicate that either substrate can fuel flight. Although hummingbirds are known to rely on fat to fuel migratory flight, short foraging bouts are fueled by the oxidation of carbohydrate, not fat. This allows birds refueling at meadows during migration to deposit fat at higher rates and avoids the energetic inefficiency that results from synthesizing fat from dietary sugar, and then breaking down the fat to fuel foraging flight. On cold mornings in subalpine meadows, refueling hummingbirds achieve net energy gain despite the high energetic costs of thermoregulation and flight. In doing so, they sustain the highest known time-averaged metabolic rates among vertebrates. However, low sucrose concentrations, provided in volumes large enough to allow the maintenance of energy balance at low temperature, result in energy deficit and mass loss. The problem of disposing of dietary water at low ambient temperature when intake rates are elevated suggests that the kidneys may be involved in establishing the upper limit to intake rates and, therefore, maximum sustained metabolic rates. It is suggested that hummingbird behaviour and metabolism have coevolved to maximize net energy gain. Further, the energetics of hummingbird thermoregulation and flight may have influenced the evolution of sucrose content in floral nectar. [Copyright &y& Elsevier]

We describe a habitat selection model that predicts the distribution of size-structured groups of fish in a habitat where food availability and water temperature vary spatially. This model is formed by combining a physiological model of fish growth with the logic of ideal free distribution (IFD) theory. In this model we assume that individuals scramble compete for resources, that relative competitive abilities of fish vary with body size, and that individuals select patches that maximize their growth rate. This model overcomes limitations in currently existing physiological and IFD-based models of habitat selection. This is because existing physiological models do not take into account the fact that the amount of food consumed by a fish in a patch will depend on the number of competitors there (something that IFD theory addresses), while traditional IFD models do not take into account the fact that fish are likely to choose patches based on potential growth rate rather than gross food intake (something that physiological models address). Our model takes advantage of the complementary strengths of these two approaches to overcome these weaknesses. Reassuringly, our model reproduces the predictions of its two constituent models under the simple conditions where they apply. When there is no competition for resources it mimics the physiological model of habitat selection, and when there is competition but no temperature variation between patches it mimics either the simple IFD model or the IFD model for unequal competitors. However, when there are both competition and temperature differences between patches our model makes different predictions. It predicts that input-matching between the resource renewal rate and the number of fish (or competitive units) in a patch, the hallmark of IFD models, will be the exception rather than the rule. It also makes the novel prediction that temperature based size-segregation will be common, and that the strength and direction of this segregation will depend on per capita resource renewal rates and the manner in which competitive weight scales with body size. Size-segregation should become more pronounced as per capita resource abundance falls. A larger fish/cooler water pattern is predicted when competitive ability increases more slowly than maximum ration with body size, and a smaller fish/cooler water pattern is predicted when competitive ability increases more rapidly than maximum ration with body size. [ABSTRACT FROM AUTHOR]

1. The metabolic or respiratory cost of growth (RG) is the increase in metabolic rate of a growing animal, and it represents chemical potential energy expended in support of net biosynthesis but not deposited as new tissue. 2. Two statistical methods (multiple non-linear regression and analysis of regression residuals) were used to calculate RG from data (n = 68) from a doubly labelled water study of free-ranging Garter Snakes (Thamnophis sirtalis fitchi) in northern California. 3. The sample-wise (‘ecological’) cost of growth was 2·07 kJ per gram of net growth (equivalent to 8·63 kJ g–1 dry tissue); reanalysis of a subset of efficient growers yielded a more conservative ‘physiological’ estimate of 1·67 kJ g–1. 4. Our empirical estimate of RG, among the first reported for squamate reptiles and free-living animals of any kind, compares closely with published, laboratory-derived values for ectotherms. 5. The metabolic costs of growth accounted for an average of 30% of total field metabolic rates for these snakes, which were growing at a mean rate of 3% of body mass per day. However, our method probably underestimated the total ecological cost of growth for large animals, because potential growth costs that covary with body size were not included. 6. Distinction between conceptual and empirical energy budgets clarifies relationships among body size, metabolic rates, and the physiological and ecological costs of growth. [ABSTRACT FROM AUTHOR]

The field metabolic rates (FMR) and rates of water flux were measured in two species of varanid lizards over five periods of the year in tropical Australia. The energetics of these species were further investigated by directly measuring activity (locomotion) and body temperatures of free-ranging animals by radiotelemetry, and by measuring standard metabolic rate (over a range of body temperatures) and activity metabolism in the laboratory. Seasonal differences in the activity and energetics were found in these goannas despite similar, high daytime temperatures throughout the year in tropical Australia. Periods of inactivity were associated with the dry times of the year, but the onset of this period of inactivity differed with respect to habitat even within the same species. Varanus gouldii, which inhabit woodlands only, were inactive during the dry and late dry seasons. V. panoptes that live in the woodland had a similar seasonal pattern of activity, but V. panoptes living near the floodplain of the South Alligator River had their highest levels of activity during the dry season when they walked long distances to forage at the receding edge of the floodplain. However, during the late dry season, after the floodplain had dried completely, they too became inactive. For V. gouldii, the rates of energy expenditure were 196 kJ kg day for active animals and 66 kJ kg day for inactive animals. The rates of water influx for these groups were respectively 50.7 and 19.5 ml kg day. For V. panoptes, the rates of energy expenditure were 143 kJ kg day for active animals and 56 kJ kg day for inactive animals. The rates of water influx for these two groups were respectively 41.4 and 21.0 ml kg day. We divided the daily energy expenditure into the proportion of energy that lizards used when 'in burrows', 'out of burrows but inactive', and 'in locomotion' for the two species during the different seasons. The time spent in locomotion by V. panoptes during the dry season is extremely high for a reptile (mean of 3.5 h/day spent walking), and these results provide an ecological correlate to the high aerobic capacity found in laboratory measurements of some species of varanids. [ABSTRACT FROM AUTHOR]

In the face of climate change there is an urgent need to understand how animal performance is affected by environmental conditions. Biophysical models that use principles of heat and mass transfer can be used to explore how an animal's morphology, physiology, and behavior interact with its environment in terms of energy, mass and water balances to affect fitness and performance. We used Niche Mapper™ (NM) to build a vervet monkey (Chlorocebus pygerythrus) biophysical model and tested the model's ability to predict core body temperature (T b) variation and thermal stress against T b and behavioral data collected from wild vervets in South Africa. The mean observed T b in both males and females was within 0.5 °C of NM's predicted T b s for 91% of hours over the five-year study period. This is the first time that NM's T b predictions have been validated against field data from a wild endotherm. Overall, these results provide confidence that NM can accurately predict thermal stress and can be used to provide insight into the thermoregulatory consequences of morphological (e.g., body size, shape, fur depth), physiological (e.g. T b plasticity) and behavioral (e.g., huddling, resting, shade seeking) adaptations. Such an approach allows users to test hypotheses about how animals adapt to thermoregulatory challenges and make informed predictions about potential responses to environmental change such as climate change or habitat conversion. Importantly, NM's animal submodel is a general model that can be adapted to other species, requiring only basic information on an animal's morphology, physiology and behavior. • A biophysical model was created and validated for wild vervet monkeys. • Core body temperature data-loggers were used to validate model predictions. • The model accurately predicted body temperature for >90% of observations. • The model was used to study thermal effects of behavior and physical traits. • The approach can test hypotheses about how animals adapt to thermal stress. [ABSTRACT FROM AUTHOR]