Cedric Zimmer

Université Sorbonne Paris Nord | Paris 13 Nord

The risk of predation directly affects the physiology, behavior, and fitness of wild birds. Strong social connections with conspecifics could help individuals recover from a stressful experience such as a predation event; however, competitive interactions also have the potential to exacerbate stress. Few studies have investigated the interaction be...

Synopsis Epigenetic mechanisms are increasingly understood to have major impacts across ecology. However, one molecular epigenetic mechanism, DNA methylation, currently dominates the literature. A second mechanism, histone modification, is likely important to ecologically relevant phenotypes and thus warrants investigation, especially because molec...

Hypothalamic–pituitary–adrenal axis (HPA) flexibility is an emerging concept recognizing that individuals that will cope best with stressors will probably be those using their hormones in the most adaptive way. The HPA flexibility concept considers glucocorticoids as molecules that convey information about the environment from the brain to the body...

Hypothalamic-pituitary-adrenal axis (HPA) flexibility is an emerging concept recognizing that individuals that will cope best with stressors will probably be those using their hormones in the most adaptive way. The HPA flexibility concept considers glucocorticoids as molecules that convey information about the environment from the brain to the body...

Although variation in effect sizes and predicted values among studies of similar phenomena is inevitable, such variation far exceeds what might be produced by sampling error alone. One possible explanation for variation among results is differences among researchers in the decisions they make regarding statistical analyses. A growing array of studi...

Epigenetic mechanisms are increasingly understood to have major impacts across ecology. However, one molecular epigenetic mechanism, DNA methylation, currently dominates the literature. A second mechanism, histone modification, is likely important to ecologically relevant phenotypes and thus warrants investigation, especially because molecular inte...

Animals encounter many novel and unpredictable challenges when moving into new areas including pathogen exposure. Because effective immune defenses against such threats can be costly, plastic immune responses could be particularly advantageous, as such defenses can be engaged only when context warrants activation. DNA methylation is a key regulator...

The social environment that individuals experience appears to be a particularly salient mediator of stress resilience, as the nature and valence of social interactions are often related to subsequent health, physiology, microbiota, and overall stress resilience. Relatively few studies have simultaneously manipulated the social environment and ecolo...

Capricious environments often present wild animals with challenges that coincide or occur in sequence. Conceptual models of the stress response predict that one threat may prime or dampen the response to another. Although evidence has supported this for glucocorticoid responses, much less is known about the effects of previous challenges on energy...

The social environment that individuals experience appears to be a particularly salient mediator of stress resilience, as the nature and valence of social interactions are often related to subsequent health, physiology, microbiota, and overall stress resilience. Relatively few studies have simultaneously manipulated the social environment and ecolo...

Studies of the evolutionary causes and consequences of variation in circulating glucocorticoids (GCs) have begun to reveal how they are shaped by selection. Yet the extent to which variation in circulating hormones reflects variation in other important regulators of the hypothalamic-pituitary-adrenal (HPA) axis, and whether these relationships vary...

The risk of predation directly affects physiology, behavior, and fitness of wild birds. Social interactions with conspecifics may affect how individuals respond to stressors such as predators. Strong social connections could help individuals recover from a stressful experience; however, competitive interactions also have the potential to exacerbate...

Animals encounter many novel and unpredictable challenges when moving into new areas including pathogen exposure. Because effective immune defenses against such threats can be costly, plastic immune responses could be particularly advantageous, as such defenses can be engaged only when context warrants activation. DNA methylation is a key regulator...

Organisms have to cope with the changes that take place in their environment in order to keep their physical and psychological stability. In vertebrates, the hypothalamic-pituitary-adrenal (HPA) axis plays a key role in mediating phenotypic adjustments to environmental changes, primarily by regulating glucocorticoids (GCs). Although circulating GCs...

As the global climate shifts, many species are imperilled by changing thermal regimes. Despite rising global temperatures, some populations must contend with more frequent or extreme cold. In these populations, the ability to cope with cold may be an important determinant of fitness. Experiments in captive animals have shown that extreme cold or ra...

Climate change is dramatically altering our planet, yet our understanding of mechanisms of thermal tolerance is limited in wild birds. We characterized natural variation in heat shock protein (HSP) gene expression among tissues and populations of free-living Tree Swallows (Tachycineta bicolor). We focused on HSPs because they prevent cellular damag...

Animals respond to sudden challenges with a coordinated set of physiological and behavioral responses that enhance the ability to cope with stressors. While general characteristics of the vertebrate stress response are well described, it is not as clear how individual components covary between- or within-individuals. A rapid increase in glucocortic...

Information theory has been applied productively across biology, but it has been used minimally in endocrinology. Here, we advocate for the integration of information theory into stress endocrinology. Presently, the majority of models of stress center on the regulation of hormone concentrations, even though what interests most endocrinologists and...

The hypothalamic-pituitary-adrenal (HPA) axis and its end products, the glucocorticoids, are critical to responding appropriately to stressors. Subsequently, many studies have sought relationships between glucocorticoids and measures of health or fitness, but such relationships are at best highly context dependent. Recently, some endocrinologists h...

Signals often covary with physiological and behavioural traits to form an axis of integrated phenotypic variation associated with reproductive performance. This pattern of phenotypic integration could result from intrinsic between-individual differences that are causally related to signal production, physiology and behaviour. Alternatively, signal...

Epigenetic mechanisms may play a central role in mediating phenotypic plasticity, especially during range expansions, when populations face a suite of novel environmental conditions. Individuals may differ in their epigenetic potential (EP; their capacity for epigenetic modifications of gene expression), which may affect their ability to colonize n...

The hypothalamic-pituitary-adrenal (HPA) axis and its end products, the glucocorticoids, are critical to responding appropriately to stressors. Subsequently, many studies have sought relationships between glucocorticoids and measures of health or fitness, but such relationships are at best highly context dependent. Recently, some endocrinologists h...

Flexibility in the regulation of the hypothalamic–pituitary–adrenal (HPA) axis is an important mediator of stress resilience as it helps organisms adjust to, avoid, or compensate for acute and chronic challenges across changing environmental contexts. Glucocorticoids remain the favorite metric from medicine to conservation biology to attempt to qua...

Glucocorticoid hormones (GCs) are central mediators of metabolism and the response to challenges. Because circulating GC levels increase in response to challenges, within-population variation in GCs could reflect among-individual variation in condition or experience. At the same time, individual variation in GC regulation could have causal effects...

The ability to respond appropriately to challenges is an important contributor to fitness. Variation in the regulation of glucocorticoid hormones, which mediate the phenotypic response to challenges, can therefore influence the ability to persist in a given environment. We compared stress responsiveness in four populations of tree swallows (Tachyci...

Responding appropriately to challenges is an important contributor to fitness. Variation in the regulation of glucocorticoid hormones, which mediate the phenotypic response to challenges, can therefore influence the ability to persist in a given environment. We compared stress responsiveness in four populations of tree swallows (Tachycineta bicolor...

Signals often covary with physiological and behavioral traits to form an axis of integrated phenotypic variation associated with reproductive performance. This pattern of phenotypic integration could result from intrinsic between-individual differences that are causally related to signal production, physiology, and behavior. Alternatively, signal e...

Vertebrates respond to a diversity of stressors by rapidly elevating glucocorticoid levels. The changes in physiology and behavior triggered by this response can be crucial for surviving a variety of challenges. Yet the same process that is invaluable in coping with immediate threats can also impose substantial damage over time. In addition to the...

Glucocorticoid hormones (GCs) are central mediators of metabolism and the response to challenges. Because circulating levels of GCs increase in response to challenges, within-population variation in GCs could reflect individual variation in condition or experience. At the same time, individual variation in the degree to which GCs increase in respon...

Stress exposure during pre and post-natal development can have persistent and often dysfunctional effects on several physiological systems, including immune function, affecting the ability to combat infection. The neuro-immune response is inextricably linked to the action of the Hypothalamic Pituitary Adrenal (HPA) axis. Cytokines released from neu...

Theory suggests that signal honesty may be maintained by differential costs for high and low quality individuals. For signals that mediate social interactions, costs can arise from the way that a signal changes the subsequent social environment via receiver responses. These receiver-dependent costs may be linked with individual quality through vari...

Individuals often vary markedly in their ability to cope with stressors, but the drivers of this variation remain poorly understood. Many studies have tested relationships among individual variation in glucocorticoid levels and the response to challenges—often finding inconsistent patterns; however, few have addressed whether variation in the capac...

The glucocorticoid stress response mediates a suite of physiological and behavioural changes that allow vertebrates to cope with transient stressors. Chronically elevated glucocorticoid levels are known to result in a variety of organismal costs, but relatively little is known about the downstream effects of mounting a series of brief, acute spikes...

Acutely stressful experiences can have profound and persistent effects on phenotype. Across taxa, individuals differ remarkably in their susceptibility to stress. However, the mechanistic causes of enduring stress effects, and of individual differences in stress susceptibility, are poorly understood. Here, we tested whether brief, acute increases i...

Circulating steroid hormone levels exhibit high variation both within and between individuals, leading some to hypothesize that these phenotypes are more variable than other morphological, physiological, and behavioral traits. This should have profound implications for the evolution of steroid signaling systems, but few studies have examined how en...

It has been well-established that there is variation in the strength and direction of the relationship between circulating glucocorticoids (GCs) and fitness. When studies demonstrate such variation or the direction of the GC-fitness relationship is unexpected, the results are often attributed to context-dependency. However, descriptors of context c...

Glucocorticoid hormones are important regulators of metabolic processes, and of the behavioral and physiological responses to stressors. Within-population variation in circulating glucocorticoids has been linked with both reproductive success and survival, but the presence and direction of relationships vary. Although conceptual models suggest the...

Maternal stress can prenatally influence offspring phenotypes and there are an increasing number of ecological studies that are bringing to bear biomedical findings to natural systems. This is resulting in a shift from the perspective that maternal stress is unanimously costly, to one in which maternal stress may be beneficial to offspring. However...

An interesting aspect of developmental programming is the existence of transgenerational effects that influence offspring characteristics and performance later in life. These transgenerational effects have been hypothesized to allow individuals to cope better with predictable environmental fluctuations and thus facilitate adaptation to changing env...

Parkinsonian patients experience not only the physical discomfort of motor disorders but also the considerable psychological distress caused by cognitive deficits and behavioral disorders. These two factors can result in a disruption of social relationships during the symptomatic and even the presymptomatic motor states of the disease. However, it...

Stress exposure during early-life development can have long-term consequences for a variety of biological functions including oxidative stress. The link between early-life stress and oxidative balance is beginning to be explored and previous studies have focused on this link in adult non-breeding or immature individuals. However, as oxidative stres...

Physiological constraints on colouration have been widely reported; especially in birds, which trade-off antioxidant responses against colourful costly signals. One female extended phenotypic trait, which might also highlight important physiological trade-offs, is the pigmentation of their eggshells. In ground-nesting species, producing eggs that a...

Stress exposure during early life development can program individual brain and physiology. The hypothalamic-pituitary-adrenal (HPA) axis is one of the primary targets of this programming which is generally associated with a hyperactive HPA axis, indicative of a reduced negative feedback. This reduced feedback efficiency usually results from a reduc...

The starvation-predation risk trade-off predicts that animals should lose some weight when facing a higher predation risk, but without impairing fasting and survival performances. This factor has led to particular concern for the conservation of the alpine rock partridge, which is known to store low fat reserves, and lives in high altitude areas su...

Prolonged exposure to stress during development can have long-term detrimental effects on health and wellbeing. However, the environmental matching hypothesis proposes that developmental stress programs physiology and behaviour in an adaptive way that can enhance fitness if early environments match those experienced later in life. Most research has...

Theoretical models of social learning predict that animals should copy others in variable environments where resource availability is relatively unpredictable. Although short-term exposure to unpredictable conditions in adulthood has been shown to encourage social learning, virtually nothing is known concerning whether and how developmental conditi...

Ljung-Box test for food intake in teal. In order to access if the data are random, we performed a Ljung-Box test that is a portemanteau test whose null hypothesis is “data are random”. (The name portemanteau test refers to a test that is made for each lag.) The tests were performed for each group of teal and each session at each lag. The p-values a...

Ljung-Box test for food intake in tufted duck. In order to access if the data are random, we performed a Ljung-Box test. The tests were performed for each group of tufted ducks and each session at each lag. The p-values are drawn in the graphic to have a better sight on the results. In the control group at session 1, for all lags, the null hypothes...

The theory of trade-off between starvation and predation risks predicts a decrease in body mass in order to improve flight performance when facing high predation risk. To date, this trade-off has mainly been validated in passerines, birds that store limited body reserves for short-term use. In the largest avian species in which the trade-off has be...

Predation directly triggers behavioural decisions designed to increase immediate survival. However, these behavioural modifications can have long term costs. There is therefore a trade-off between antipredator behaviours and other activities. This trade-off is generally considered between vigilance and only one other behaviour, thus neglecting pote...

The debate concerning the relative importance of the costs and benefits of parental investment decisions has created considerable controversy. This is especially true in the discussion for duck species, where the link between ending of parental care and offspring survival has not been fully determined. This experimental study tests whether mallard...

For passerines the starvation-predation risk theory predicts that birds should decrease their body mass to improve escape flight performance, when predation pressure increases. To investigate whether this theory may apply to large birds, which manage body reserves differently from small passerines, we experimentally increased the predation risk in...

Impact d'un dérangement sur la balance énergétique, le comportement et la reproduction d'Anatidés: généralisation du compromis entre le risque de jeûne et le risque de prédation

Theoretical models of sexual selection predict that both males and females of many species should benefit by selecting their mating partners. However, empirical evidence testing and validating this prediction is scarce. In particular, whereas inbreeding avoidance is expected to induce sexual conflicts, in some cases both partners could benefit by a...

In birds, the link between parental care behaviour and prolactin release during incubation persists after hatching in altricial birds, but has never been precisely studied during the whole rearing period in precocial species, such as ducks. The present study aims to understand how changes in parental care after hatching are related to circulating p...

Mate choice theories predict that animals evolved strategies to mate with optimally genetically dissimilar partners, providing fitness benefits. In group-living species, when adults do not disperse, assessment of relatedness between conspecifics can be a key factor for choosing mates. Here, we report for the first time, kin recognition abilities an...