Cooperative breeding, where seemingly altruistic helpers forgo reproduction to assist in raising the offspring of others, is a puzzle for biologists because it appears to contradict evolutionary principles of selfishness. One potential explanation is that helpers enhance group productivity, thus improving the direct fitness of breeders and providing indirect genetic and group-living benefits for helpers. In many species, however, helper presence does not actually enhance offspring production, raising the question of whether helpers instead either improve offspring quality (rather than quantity) or allow breeders to reduce prenatal investment (thereby increasing breeders' condition and future reproduction). In arrow-marked babblers (Turdoides jardineii), helpers do not increase the number of fledglings produced. To test whether helpers instead improve offspring quality or compensate for reduced prenatal investment, we investigated how egg volume, offspring growth, and nestling provisioning rates vary with group size. Breeding females in larger groups laid smaller eggs, but also produced heavier fledglings than those from smaller groups. This suggests that helpers in larger groups not only facilitate reduced prenatal maternal investment, but actually over-compensate for reduced egg sizes. Interestingly, larger groups did not feed nestlings more, suggesting that over-compensatory nestling growth may result from larger groups providing higher-quality food. Our results show that helping can be selected for via different mechanisms acting on both breeders and offspring, and that these can apply simultaneously within a single species. We highlight that variation in life history may explain inter-specific differences in mechanisms by which helpers improve group productivity.
Prey often assess predation risk using multiple sources of information that differ in immediacy and reliability. How prey differentially weight direct predator-associated cues and heterospecific alarm cues remains a central question in behavioral ecology. To investigate this, playback experiments were conducted on free-ranging, predator-experienced Southern giraffes (Giraffa giraffa), using lion (Panthera leo) vocalizations and red-billed oxpecker (Buphagus erythrorhynchus) alarm calls presented in different positions within sequential playback trials. Lion vocalizations consistently elicited strong vigilance responses regardless of playback presentation order, indicating that giraffes assigned greater behavioral weight to direct predator-associated information. Giraffes also responded to oxpecker alarm calls, although responses were generally weaker and more variable than responses to lion vocalizations, suggesting that indirect heterospecific cues were weighted less strongly than direct predator cues. Evidence that preceding playback exposure strongly influenced subsequent vigilance responses was limited, as lion vocalizations continued to elicit stronger responses than oxpecker alarm calls across successive playbacks. Females additionally exhibited generally stronger vigilance responses than males across playback conditions. Together, these findings suggest that giraffes differentially weight multiple sources of risk-related acoustic information during antipredator responses.
Discrete color polymorphisms often correlate with other traits, forming suites of characteristics that may be signaled and inform mate-choice decisions and/or dominance interactions with conspecifics. Unraveling the adaptive function and maintenance of stable color polymorphisms thus requires understanding these links and the context in which color traits are used. Here, we conducted a field experiment with robotic models to study the relationship between color morph, territorial behavior,, and circulating hormones, namely testosterone and corticosterone, in a male-male competition framework using the color polymorphic lizard Sceloporus consobrinus. We found that yellow and orange male color morphs are conspicuous and can be reliably distinguished by conspecifics, making color differences suitable for morph-specific signaling. Orange males exhibited higher baseline rates of push-up displays and bouts of movement compared to yellow males. Lizards of both morphs strongly increased aggressive display behavior in response to intruder robotic models of either the same or different color morph. However, color morphs did not differ in body size (SVL), body condition or plasma hormonal content (testosterone and corticosterone), suggesting that color could convey information regarding alternative territorial behavior but does not signal differences in individual male "quality" or physiological hormonal state. Color may thus not be sufficient, or the most informative signal in the context of agonistic male contests. Aggressive motion displays may be more effective as a signal of a morph's resource holding potential than static color. The lack of convergence in correlated phenotypes across similarly polymorphic taxa further suggests that patterns of trait integration are rather species-specific.
Consistent individual differences in animal behavior-ie, personalities-have been documented in many taxa to have important fitness consequences in the context of predator-prey interactions. Multiple mechanisms have been suggested to maintain variation in prey personality traits, including life-history tradeoffs and divergent selection pressures from predators with different hunting strategies. However, empirical evidence for these hypotheses has been limited by a lack of data originating from complex multipredator systems in situ. To address this gap and evaluate these 2 mechanisms, we collected hispid cotton rats (Sigmodon hispidus) in the Florida Everglades and quantified 3 behavioral traits in the field. After releasing rats at their point of capture, we monitored their survival in their natural habitat where they faced threats from a diversity of ambush (snakes) and active predators (mammals; birds). Using Cox proportional hazards regression models and competing risks models, we assessed the effect of boldness, activity, and docility on rodent predation risk. Contrary to conventional predictions that bolder and more active individuals would face higher predation risk due to life-history tradeoffs, we found that the impact of these traits on prey survival varied with the predators' hunting modes: shyer, more active individuals were more likely to be killed by active predators, whereas less active rats appeared more likely to be killed by ambush predators. Our study supports the hypothesis that a diversity of predator hunting strategies may help maintain trait variation in prey populations.
Abstract How collective behaviors emerge from group members with potentially divergent needs remains poorly understood in many social species. Giraffes are known to exhibit substantial social fluidity, given the high degree of fission-fusion dynamics that shape their grouping patterns. However, the patterns and processes underlying giraffe collective movements remain unknown. Using behavioral observations, we examined how individual factors (sex and age), social context (group size and type), and habitat characteristics (open and closed) influence the decision-making process that shapes giraffe collective movements and resultant group fission. We found that adult females were more likely to initiate group movements, whereas subadults followed movements more quickly than other age classes. Decision-making for collective movements was slower in larger groups than in smaller ones. Consequently, movements in larger groups were more likely to result in group fission. These results contribute to a growing body of knowledge on the coordination of collective movement across species. By illuminating collective movement dynamics in an understudied large mammal species with a high degree of fission-fusion dynamics, we contribute to the potential for cross-species investigations into the mechanisms of collective behavior and the factors that drive inter- and intraspecific variation.
Abstract Early environmental conditions play an important role in animal development. Lack of sufficient food early in life can lead to impaired growth and long-term fitness consequences. To avoid that, many animal species compensate during a period of low food availability by increasing their growth rate when food becomes abundant again, i.e. compensatory growth. However, compensatory growth during development may divert resources away from the ontogeny of reproductive and somatic functions, imposing hidden costs that are only apparent later in life. For ectotherms, these trade-offs are expected to be exacerbated by increased temperatures due to the high energetic demands of increased metabolism. We test if diet restriction during early development has long-term effects on the reproductive traits of male Trinidadian guppies (Poecilia reticulata); and if so, whether such effects are exacerbated in warmer temperatures. Previously, we have shown that diet-restricted guppies exhibit compensatory growth. Here, we found that diet restriction during early development had no effect on the expression of sexual traits later in life. In contrast, males experiencing elevated temperatures throughout life exhibited a reduction in both black body colouration and dominance behaviours and died younger. Surprisingly, temperature did not mediate the effects of early-life diet on male sexual traits. However, temperature did mediate the effects of diet on adult growth, with diet-restricted males showing impaired growth later in life but only when they experienced elevated temperatures. Our results highlight the developmental plasticity of sexual traits and suggest that future climate predictions have the potential to negatively affect fish reproduction.
Abstract Parasites frequently manipulate host behavior to increase their own fitness, but the proximal mechanisms underlying these manipulations remain poorly understood. In interactions between polysphinctine parasitoid wasps and spiders, hosts are induced to build modified and more resistant webs (cocoon webs). This construction is currently attributed to the activation of the host's innate ecdysis mechanism, based on the cocoon web's similarity to spider molting webs and the association with elevated levels of the hormone 20-hydroxyecdysone (20E) in Araneidae species. However, the only empirical evidence of 20E enhancement is taxonomically restricted, limiting generalization. In this study, we investigated this ecdysis-based manipulation mechanism in a Tetragnathidae spider host. Examining the interaction between the spider Leucauge volupis (Keyserling, 1893) and the polysphinctine wasp Hymenoepimecis cameroni (Townes, 1966), we compared the architecture of normal, molting, and cocoon webs of the spider, and quantified 20E levels across the spider's group. Cocoon webs shared traits with molting webs, such as the absence of sticky spirals and increased reinforced radii. However, contrary to expectations, 20E levels were not elevated in behaviorally altered spiders compared with the other groups. Therefore, although cocoon webs resemble molting webs, ecdysone does not appear to be the proximate trigger of host manipulation in this system, suggesting that their structural similarity arises from alternative physiological or behavioral pathways yet to be identified.
Courtship displays often consist of more than 1 modality, despite additional costs associated with multiple modalities. Because courtship signals under strong sexual selection often show heightened condition dependence, they may convey information about mate quality. However, much of the research on condition dependence has focused on individual modalities. Theoretically, different modalities within 1 multimodal signal could show different degrees of condition dependence, depending on how strong the selection pressure is on each modality. Here, we investigate how male condition affects the multimodal courtship of the parasitoid wasp Leptopilina heterotoma. Specifically, we tested how 2 components of the multimodal courtship-a chemical signal (cuticular hydrocarbons, CHCs) and a vibratory signal (wing fanning)-are affected by age and nutritional state. We found that the 2 modalities responded differently to the male condition: Wing fanning was affected by both age and nutrition, whereas the chemical profile was only affected by age. In combination with previous studies, we conclude that wing fanning signals male quality and thus should be condition dependent, while the CHC profiles signal species identity and should remain stable. This further supports that L. heterotoma has a multimodal courtship display that conveys multiple messages. Additionally, we show that males increase their wing fanning frequency when mounted on the female. This behavioral adjustment during the courtship sequence is likely an energy-saving strategy, given the high energetic cost of wing fanning.
Pharmaceutical pollution is a global environmental threat, with antidepressants contributing a substantial proportion of pharmaceutical contaminant detections worldwide. The antidepressant fluoxetine is commonly detected in aquatic environments and has been reported to impact ecologically important behavioral and physiological traits in exposed wildlife. However, relatively few studies have examined possible effects of fluoxetine on both behavior and metabolic rate, particularly over ecologically relevant exposure timescales. Accordingly, we investigated the impacts of long-term fluoxetine exposure on foraging and antipredator behavior, metabolic rate, and morphology in female guppies (Poecilia reticulata). Fish were exposed to 1 of 3 treatments-an unexposed control (0 ng L-1), or low or high fluoxetine (mean measured concentrations: 30 ng L-1 and 292 ng L-1, respectively)-for 8 mo in a semi-natural mesocosm system, corresponding to ∼2 to 3 overlapping generations. Following exposure, we quantified foraging and antipredator behavior in the presence or absence of a live predator, the spangled perch (Leiopotherapon unicolor). We then measured the rate of oxygen consumption ( V ˙ O2) of the guppies as a proxy for standard metabolic rate, and recorded mass, standard length, and body condition as morphological measurements. Our results show that long-term fluoxetine exposure did not significantly affect the behavior, metabolic rate, or morphology of female guppies. Considered alongside previous work, our findings emphasize the importance of exposure duration in mediating the impacts of fluoxetine on fitness-related traits, with continued research being essential in identifying potential mechanisms that underpin these findings.
Individual phenotypes strongly affect dispersal. Yet studying the relationship between dispersal tendencies and personality under ecologically relevant conditions is challenging, especially in fish. Laboratory studies lack environmental complexity and scale, while field-based approaches are often unfeasible. We here mimicked dispersal events in fish; encompassing all 3 phases of dispersal (departure, transience, settlement) in a large experimental mesocosm containing breeding sites. Using 3-spined sticklebacks (Gasterosteus aculeatus) tagged with 'Passive Integrated Transponders' (PIT tags), we remotely monitored proxies of dispersal of 2 cohorts, each consisting of 40 individuals of known activity and aggressiveness scores, continuously over 2 wk. We tested whether personality variation explained differences in departure timing, transience movements, settlement success and spatial distribution along the environmental gradient. We found that more active/aggressive individuals dispersed quicker in the mesocosm, spent more time on territories and collected more eggs. However, we did not detect strong phenotype-environment correlations. Our findings emphasize the potential role of personality-dependent dispersal in population dynamics, with specific behavioral types driving dispersal and settlement success. Our mesocosm setup provides unique insights into the dispersal dynamics in a system where detailed observations across all dispersal stages are rare and difficult to obtain. Despite limitations, behavioral experiments in mesocosms serve as a valuable bridge between laboratory and natural systems.
Polyandry is widespread across animals, yet its underlying causes and consequences remain unclear in natural populations. Recent work suggests that spatial and temporal variation in the environment shape the causes and consequences of polyandry. Here, we extend this research by testing whether one consequence of polyandry, multiple paternity, is influenced by females' social environment, specifically the prevalence of male alternative reproductive tactics (ARTs), territorials and roamers. We studied semi-natural populations of house mice (Mus musculus domesticus) under different food quality treatments. Doing so allowed us to explore whether the relationship between male ARTs and multiple paternity depends on environmental conditions, which are expected to mediate the relative costs and benefits of reproductive investment. Using microsatellite genotyping, we assigned paternity to 329 litters produced by 257 females across 5 generations. We then classified the sires of these litters as territorials or roamers based on their reproductive behavior around conception and quantified each sire's reproductive contribution to each litter. Multiple paternity was strongly associated with the presence of roamers, which were twice as likely to occur in multiple-sired litters compared with territorials. Territorials still sired most offspring, an effect consistent with roamers engaging in sneaky/opportunistic matings. However, we found no clear evidence that environmental conditions shift how ARTs contribute to multiple paternity. Together, our results demonstrate a tight link between female mating outcomes and male ARTs across environments, implying that the drivers of polyandry depend on the social environment. By explicitly linking ARTs to multiple paternity, our study provides a mechanistic understanding on how social dynamics shape reproductive outcomes in mating systems where both sexes mate multiply.
Wind conditions play a major role in determining how birds negotiate ecological barriers during long-distance migration. Migrants typically minimize flights over barriers in opposing winds, while crossing the same barriers directly in supportive winds. Nevertheless, even in supportive conditions, direct barrier-crossings may be associated with an elevated risk of fatigue. At the same time, barrier-crossings may be facilitated by the availability of steppingstones. We aimed to understand how seasonal ocean-crossings of Eleonora's falcons (Falco eleonorae) compare in terms of wind support, flight effort, and the use of remote islands. To do this we combined over a decade of GPS-tracking data from 19 individuals (2012 to 2022) with wind data from an atmospheric reanalysis model. Despite far greater wind support in spring, falcons achieved similar ground speeds in both seasons, because they flew at much lower airspeeds in spring (8.8 ± 1.7 m/s) than in autumn (13.2 ± 2.6 m/s). Overall, it took falcons twice as many flight hours to complete a 40% greater air distance in spring compared with autumn. More islands are available along the spring route, and 57.9% of falcons used an island during at least 1 spring crossing, compared with 21.1% in autumn. In spring, island use increased with weaker wind support, with falcons spending the night on islands, and apparently maximizing daytime flight by initiating ocean-crossings at dawn. Overall, wind conditions only partially offset the seasonal difference in falcons' crossing distance and effort. Isolated islands may be an overlooked factor explaining the configuration of falcons' ocean-crossing corridors.
Foraging animals need to balance the trade-off between the benefits of exploiting new resources and the unknown risks they entail. Changing environments are especially challenging, as this balance between risk and reward needs to be constantly reevaluated. One strategy animals, and in particular scavengers employ, is using conspecifics and heterospecifics as sources of information to access food. In this study, we focused on free-ranging ravens that habitually forage in a wildlife park together with heterospecifics (boars) and tested their responses to unfamiliar and unpredictable foraging situations. In the 2-sites experiment (E1), we presented them with a choice between an unfamiliar (new) and a familiar (old) foraging site; in the object experiment (E2), we presented them with an object, otherwise not seen in the wildlife park, positioned randomly next to 1 of the sites. In both experiments, we found that ravens delayed their initial approach until the boars reached the food. In E1, ravens took longer to approach the food; stole more food from conspecifics but visited in larger numbers at the new site compared with the old. In conclusion: they flexibly used others, including heterospecifics, as sources of knowledge and means to access food. In E2, the object had a stronger aversive effect at the old site than at the new site, suggesting that the effect of unpredictability is stronger in familiar environments, where it might cause an expectancy violation. Our findings highlight that the behavior toward conspecifics and heterospecifics should be considered when studying scavengers' adaptability to changing environments.
Temperature and oxygen concentration can alter the behavior of animals. While often studied in isolation, these factors frequently co-occur. Together they may have nonadditive effects. The effect of abiotic stressors may also change in the presence of biotic stressors, like predators, due to altered costs and benefits of behaviors. Additionally, species may balance the demands of co-occurring stressors differently depending on their unique needs. Here, we investigated the effects of acute exposures to elevated temperature (16 °C versus 12 °C) and decreased dissolved oxygen (30% versus 100% DO) on the social behavior and activity of two co-occurring freshwater fish (common minnow, Phoxinus phoxinus, and three-spined stickleback, Gasterosteus aculeatus) before and after a simulated predator attack. Prior to the release of the model predator, the effect of one stressor was dependent on the other stressor in minnows. Evidence suggested that minnows were more social in warmer waters, but only in hypoxic conditions, and were less active under hypoxia, but only in warm water. Sticklebacks were more active in warm water at both oxygen concentrations. Following predator release, there were no differences in social behavior, likely because of overall reductions in activity. Our study highlights the need to consider stressor combinations. Minnows appeared to compensate for one abiotic stressor such that effects were only apparent when the stressors were experienced together. However, the arrival of the "predator" masked differences between the treatment groups. Different responses between the species suggest that studies in species interactions are needed to understand community level impacts of multiple stressors.
When birds breed in multiple years, they can either return to their former breeding site or disperse to a new area. Consistent with theoretical predictions, the degree of breeding site fidelity often differs between the sexes in relation to the mating system of a species. However, most research has focused on species with conventional sex roles. Studying socially polyandrous species, in which typical sex roles are reversed, may provide insights into the drivers of breeding site fidelity in each sex. We color-banded 169 male and 184 female red phalaropes Phalaropus fulicarius, a species in which females compete for access to males (female access polyandry), and examined factors that predicted their return to the study area. Breeding site fidelity was relatively low, but substantially higher in males (20.7%) than in females (4.3%). For both sexes, the probability of returning was associated with local breeding performance: males that attended a nest in the study area were more likely to return than males without a nest, and females that locally bred with 2 males were more likely to return than those that only produced a clutch for a single male. Our findings are consistent with the prediction that site fidelity should be male-biased in species with a female-access polyandrous mating system. Our study also highlights that breeding site fidelity is associated with local breeding success, even in a species that shows a reversal of typical sex-roles, where individuals do not defend a territory, and breed in an environment that is highly unpredictable between years.
Individual dietary variation in sexually dimorphic predator populations arises from phenotypic traits, preference, prey availability, and competition. We tested competing hypotheses for how diet similarity among cougars (Puma concolor) is influenced by sex, seasonal prey availability, and home range overlap in the southern interior of British Columbia, Canada. We proposed 4 hypotheses: (i) prey availability-overlapping individuals share similar diets due to access to the same prey base; (ii) resource competition-overlapping individuals diverge in diet to minimize competition; (iii) resource partitioning-diet similarity peaks at intermediate overlap; and (iv) null-sex and season explain similarity irrespective of overlap. We analyzed diet data from 27 female and 11 male cougars (875 kill sites) and extrapolated prey availability from 146 remote cameras to test for sex-based differences in prey selection across winter, migration, and summer. We then used a pairwise approach to model diet similarity between individuals. Males generally killed larger prey (eg, moose, elk), while females killed more deer, with differences in deer species selection in the Boundary study area where fewer large prey were available. We found support for resource partitioning between female-female dyads and for resource competition between male-female dyads. Diet similarity was lowest in summer when home ranges were largest and highest in winter when ranges were smallest. Our findings highlight the complexity of predation patterns and the roles of sexual dimorphism, seasonal prey availability, and resource partitioning in shaping prey use among spatially overlapping territorial predators in multiprey systems.
Abstract In contests over resource access, competitors aim to win, gaining or retaining the resource while minimizing the costs of fighting. Considerable research has tested contest “assessment strategies”, which describe how animals gather information about fighting ability, resource ownership, resource value, and other factors, and how this information informs fighting effort. Historically, assessment strategies were considered fixed within a population or species, yet in recent years there has been a push to quantify how strategies vary according to resource ownership or inherently among individuals. We tested for variation in the assessment strategy of competing Gonodactylus childi, an Indo-Pacific species of mantis shrimp (Stomatopoda) that exchanges high-force strikes during contests over access to protective burrows: holes in dead coral or rock. By staging contests over access to a mock burrow, we found that larger individuals won more often, but “residents” already in the burrow were most likely to win. Our results most closely supported a self-assessment fighting strategy in residents only: losers based their fighting effort on their own body size, and not that of eventual winners. Analyses of contest behavioral progressions showed little ability to discriminate assessment strategies. Finally, we revealed among-individual variation that was unexplained by factors like resource ownership. We compare our results to a prior study of an ecologically similar and closely related mantis shrimp that assesses both own and opponent fighting ability. Overall, our results highlight multiple axes of variation that, while informing future theory, form the substrate for behavioral evolution in contests.
Abstract Predator-prey interactions represent one of the most significant forms of interspecific communication in natural ecosystems. It shapes population dynamics, evolution, and stability. However, the predator-prey interactions in subterranean environments are poorly understood due to the baren subterranean niche that restricts most forms of sensory communication. In this study, we compare anti-predator responses of 2 small sympatric herbivores; the subterranean plateau zokor (Eospalax baileyi), and surface-dwelling plateau pika (Ochotona curzoniae). In a series of experiments, zokors and pikas were exposed to different predator odors and distilled water as a control. For both species, we measured foraging and anti-predator behaviors, stress hormones, hypothalamic corticotropin-releasing factor (CRF), and c-fos mRNA expressions. Compared with the control group, the feeding time and food consumption of both species in the treatment groups were significantly reduced compared with the control group. Anti-predatory behavioral responses, such as freezing and climbing, significantly increased for both species. However, there were some species-specifics behavioral alterations as the presence of predator odor significantly increased locomotion in zokor but decreased locomotion was observed in pika. There was no difference between controls and treatments in hiding and head-out behaviors displayed by zokor, but there was a significant increase for the previous behavioral changes in the treatment groups in pika. For both species, the serum levels of adrenocorticotropic hormone, corticosterone, hypothalamus CRF, and c-fos mRNA expressions, were significantly higher in the predator odors groups. Our study demonstrates that subterranean life can alter prey behavior without changing physiological anti-predator responses.
Abstract Climate change is predicted to increase incidents of heat stress, which is known to impair cognitive performance. Associative learning, a highly conserved cognitive trait, is thought to underpin anti-predator behaviour, though direct empirical evidence is lacking from natural populations. If true, this would imply that environmental stressors, such as heat stress, may affect the ability of wild animals to respond to predators. However, the effect of heat stress on the link between associative learning and anti-predator behaviour has received limited empirical attention. Using wild Western Australian magpies (Gymnorhina tibicen dorsalis), we investigated 1) whether associative learning predicts anti-predator behaviour, and 2) whether this relationship is influenced by heat stress. We predicted that birds with better associative learning performance would respond more strongly to a simulated predator threat, but that this relationship would be significantly weakened by heat stress. Consistent with our first prediction, we found that individuals with higher associative learning performance were more responsive to the simulated predator threat. Contrary to our second prediction, heat stress did not disrupt the relationship between associative learning performance and vigilance. Rather, individuals with better associative learning produced more alarm calls and took longer to return to normal behaviour under heat stress. These findings provide some of the first empirical support for the hypothesized link between associative learning and anti-predator behaviour in a wild bird population. Furthermore, they suggest that associative learning may facilitate behavioural adaptation to challenging environmental conditions by enabling individuals to integrate cues such as temperature into context-appropriate anti-predator responses.
Abstract Metabolism and activity should be tightly linked; metabolism provides energy for activity, and general activity may often affect the rate at which animals acquire resources that drive metabolism. However, little is known about the ways metabolism and activity covary in ecologically germane contexts in natural populations. To explore this in more detail, we collected repeated measures of instantaneous metabolic rates and associated changes in activity levels in house sparrows (Passer domesticus) in response to shifts between stimulated and unstimulated contexts. Using a reaction norm approach and mixed-effects models, we examined among-individual variation in metabolism during inactivity (intercept/resting metabolic rate; RMR) and the rate of change in metabolism associated with changes in activity and time since a transition in the level of external stimuli (slope/metabolic plasticity). Individuals exhibited significantly repeatable differences in both inactive metabolism and metabolic slopes with respect to time (but not activity) during stages of the experiment designed to ramp up or ramp down responses. Individuality persisted after accounting for potential causes of variation. Our results indicate consistent differences in how individuals alter metabolic rate across time after changes in stimulation, raising questions about underlying processes contributing to and maintaining such variation. Similar analyses incorporating physiological and life history traits may reveal important relationships that allow for the maintenance of individual variation in metabolic plasticity. Our framework of treating metabolic rate as a reaction norm across time and activity uncovers ecologically relevant individual variation that holds promise for further investigations into the context-dependent link between metabolism and behavior.
