Defensive plasticity in South American rattlesnakes Crotalus durissus

Correction to: 'How do developmental and parental exposures to predation affect personality and immediate behavioural plasticity in the snail Physa acuta?'

Animal 'personalities' or behavioural syndromes can be defined as individual differences in suites of correlated behaviours. Using chaffinches Fringilla coelebs temporarily held in captivity, we determined the extent to which activity level (AL), the behavioural response to a stressful situation (BRSS) and two anti-predation risk behaviours when exposed to a model predator were inter-correlated within individuals. We assayed AL and BRSS when the chaffinches were first put in an experimental room. Subsequently we recorded their initial response (freeze or escape) to the sudden appearance of a model hawk, in addition to their latency to resume activity afterwards as a measure of cautiousness ('latency'). Each bird was assayed in two situations that differed in the risk level posed and in the assumed optimal response required to minimize predation risk: (1) high risk, when the hawk flew directly over the chaffinch and the assumed optimal response was to escape; and (2) low risk, when the model hawk flew 2 m to the side of the chaffinch and, since the bird was not being targeted, the assumed optimal response was to freeze in order to avoid attracting attention. All of the variables had relatively high repeatabilities and were inter-correlated, providing strong evidence for a behavioural syndrome. Though propensity to freeze was much greater in the low risk treatment, AL was negatively correlated with freezing behaviour in both risk treatments, and therefore there was a 'behavioural carryover' across situations. While hypoactive individuals were more likely to freeze in the low risk treatment, and were therefore assumed to be better able to assess risk compared to hyperactive individuals, some hypoactive individuals also froze in the high risk situation when it was assumed to be inappropriate to do so. Despite this apparently maladaptive behaviour in the high risk situation, overall hypoactive individuals showed a greater degree of behavioural plasticity across treatments compared to hyperactives. Taken together our results support the hypothesis of differential predation risk among personality types. We discuss the implications of our results for current interest in personalities, and for predation risk and group-living theories.

Predator odors are natural stressors that induce anti-predator defensive responses, which have developed under evolutionary pressures to maximize the fitness of an individual to avoid dangerous confrontations. In this study, we analyzed the defensive responses of a subterranean rodent species, the plateau zokor (Eospalax baileyi), to predation threat, and examined the trade-offs between defensive responses and foraging. Plateau zokors were exposed to 1, 3, and 6 g of eagle owl (Bubo bubo) feces, and the anti-predator behavioral, hormonal, and hypothalamic corticotropin-releasing factor and c-fos mRNA expression responses were analyzed and compared with the control (distilled water). Exposure of the animals to owl feces led to significant reductions in both duration of feeding and amount of food consumed, while some defensive behavioral responses (e.g., freezing and rearing) were more significant in the exposed animals than in the control. Serum levels of adrenocorticotropic hormone and corticosterone in plateau zokors exposed to owl feces were significantly higher compared with the control. The hypothalamic corticotropin-releasing factor and c-fos mRNA expression levels of plateau zokors exposed to 1, 3, and 6 g owl feces increased significantly, concomitant with the amount of eagle owl feces presented. Owl feces induced various behavioral, hormonal, and hypothalamic gene expression changes in plateau zokors exposed to them. Some behavioral and gene expression (but not hormonal) responses appeared to be threshold dependent. Predator odors supersede other signals and can provide comprehensive information to prey during life-threatening events. The plateau zokor is a typical subterranean rodent living in dark and enclosed subterranean habitats. Owing to this special habitat, zokors may be able to recognize ground predator odors and respond defensively. We investigated changes in behavior, hormones, and the hypothalamic corticotropin-releasing factor and c-fos mRNA expression levels of the plateau zokor when exposed to different amounts of eagle owl feces. We believe that our study makes a significant contribution to the literature because our results support the predation risk allocation hypothesis, showing that eagle owl feces inhibit foraging and induce various anti-predatory behavioral and neuroendocrine responses in plateau zokors.

Antiparasite behavior

Anti-predator behavior of squid throughout ontogeny

Threat intensity widens fear generalization gradients.

Fixed behavioural plasticity in response to predation risk in the three-spined stickleback

We conducted an experiment to assess the change in foraging efficiency resulting from diet-induced morphological and behavioural plasticity in a species of freshwater, threespine stickleback (Gasterosteus sp.). Different degrees of morphological and behavioural change were induced using two prey items commonly found in the diet of this species, allowing us to estimate the relative importance of each type of plasticity. The purpose of the experiment was twofold. First, earlier work had suggested that diet variability might be an important factor in the evolution of trophic morphological plasticity in sticklebacks. The present results extend this work by revealing the adaptive significance of morphological plasticity. The current experiment also qualitatively assessed the compatibility of the time scale of morphological change with that of the natural resource variability experienced by this species. The results indicate that diet-induced plasticity improves foraging efficiency continuously for up to 72 days of prey exposure. This is probably due in part to plasticity of the external trophic morphology but our results also suggest a complex interplay between morphology and behaviour. The time scale appears to be matched to that of natural diet variability although it is possible that some traits exhibit non-labile plasticity. Our discussion highlights the important distinction between conditions favouring the evolution of labile versus non-labile plasticity. The second objective of the experiment was to determine the relative importance of morphological and behavioural plasticity. Few studies have attempted to quantify the adaptive significance of morphological plasticity and no study to our knowledge has separated the effects of morphological and behavioural plasticity. Our experiment reveals that both behavioural and morphological plasticity are important and it also suggests a dichotomy between the two: behavioural plasticity predominately affects searching efficiency whereas morphological plasticity predominately affects handling efficiency.

BackgroundIn prey, patterns of individual habitat selection and movement can be a consequence of an individuals’ anti-predator behavior. Adjustments of anti-predator behavior are important for prey to increase their survival. Hunters may alter the anti-predator behavior of prey. In long-lived animals, experience may cause behavioral changes during individuals’ lifetime, which may result in altered habitat selection and movement. Our knowledge of which specific events related to hunting activity induce behavioral changes in solitary living species is still limited.MethodsWe used offspring loss in a solitary and long-lived ungulate species, moose (Alces alces), as our model system. We investigated whether offspring loss to hunters induces behavioral changes in a species subjected to heavy human harvest but free from natural predation. To test for behavioral change in relation to two proxies for experience (calf fate and age), we combined movement data from 51 adult female moose with data on their offspring survival and female age. We tested for adjustments in females’ habitat selection and movement following calf harvest using Hidden Markov Models and integrated Step Selection Analysis to obtain behavioral state specific habitat selection coefficients.ResultsWe found that females with a harvested calf modified habitat selection and movement during the following hunting season. Female moose selected for shorter distance to roads during the night, selected for shorter distance to forests and greater distance to human settlements following calf harvest than females who had not lost a calf. The survival of twins in a given hunting season was related to female age. Older females we more likely to have twins survive the hunting season.ConclusionsOur findings suggest that losing offspring to human harvest imposes behavioral changes in a long-lived ungulate species, leading to adjustments in females' habitat selection and movement behavior, which may lower the risk of encountering hunters. In our study, female moose that experienced calf loss selected for lower distance to forest and selected for greater distance to human settlements during periods of high hunting pressure compared to females without the experience of calf loss during the previous hunting season. We interpret this as potential learning effects.

PurposePreserving the environment is fundamental to the planet’s long-term sustainability, but attempts to promote pro-environmental behaviours often do not take into account the motivational determinants of such behaviours. This study aims to present and critically evaluate the theoretical and empirical basis of goal-framing theory, which asserts that pro-environmental behaviours might stem from conflicting goals. This study compares the theory to other approaches used to explain pro-environmental behaviour, reviews the empirical evidence for it and comes up with suggestions for future research.Design/methodology/approachThis study compares the theory with other popular theories to explain pro-environmental behaviour and behaviour change and systematically review 25 empirical research studies that adopt the goal-framing theory.FindingsMost studies rely on survey data, focus on Europe and gather self-reported behaviours or hypothetical responses. Furthermore, many studies of goal frames neglect key situational factors. Thus, the directions for further research outlined herein emphasise the need for more experimental studies of real behaviours, with consideration of situational factors, using methods that can explicate unconscious processes too. Overall, goal-framing theory provides a promising approach for analysing pro-environmental behaviours, in that it explicitly deals with goal conflicts, takes situational factors into account and encompasses conscious and unconscious processes. The authors conclude that the theory can form a useful basis for the design of social marketing behavioural interventions to promote pro-environmental behaviours.Originality/valueTo the best of the authors’ knowledge, as the first systematic review of empirical applications of goal-framing theory, this study provides refinement and validation. By also offering propositions and a research agenda, the authors hope to inspire researchers in social marketing to address the remaining gaps and refine the theory even further.

I studied antipredator behavior in two species of monkeys to elucidate the role of predation in shaping the social systems of arboreal primates. I compared the responses of monkeys to auditory and visual contact with predators to response elicited by sound playback experiments using the recorded calls of predators. Changes in vigilance and aggregation persisting up to 30 min after predator encounter occurred in both cases. Measures of vigilance shed light on individual perceptions of risk, while aggregation measures—intragroup spatial cohesion and polyspecific associations—permit direct inference about the protective benefits of grouping for the monkeys. They responded to real predator encounters and simulations in similar ways. Thus, sound playbacks of predator vocalizations are effective to simulate predator proximity. Contrary to predictions, predator encounters did not lead invariably to increased cohesion within groups or to increased time spent vigilant. Moreover, behavior in polyspecific associations was no different from that in single-species groups. Only red colobus encountering chimpanzees behaved as predicted by increasing vigilance and intragroup cohesion. The red colobus social system may have developed to protect against chimpanzee attack. In contrast, red-tailed monkey encounters with raptors and chimpanzees involved no change in time spent vigilant, coupled with decreases in intragroup cohesion. I conclude that predation is not a uniform selective pressure and patterns of social behavior within groups do not predict antipredator behavior.

Attentive immobility is a defensive state that prepares organisms for adaptive responses to imminent threats. In humans, it has been associated with a multimodal pattern of heart rate bradycardia, elevated skin conductance, freezing of gaze, and reductions in visuocortical alpha power to enhance perceptual processing and action preparation. However, the extent to which these processes are shaped by threat intensity or rather reflect stereotypic response patterns remains elusive. Here we combined avoidable and inevitable threats with different shock intensities to dissociate threat intensity from action preparation in defensive responding. Forty-eight participants observed naturalistic images while electrocortical activity, heart rate, skin conductance, pupil dilation, and eye movements were recorded. The color and shape of the cue preceding each trial were indicative of the trial type and predicted an inevitable or avoidable high or low-intensity painful stimulation after the picture offset. Results showed stronger gaze centralization in avoidable trials, indicating enhanced action preparation. Skin conductance primarily reflected threat intensity, while heart rate, alpha power reduction, fixation durations, and pupil dilation varied with both threat intensity and action readiness. The interplay between these components suggests a need to move away from the notion of separate systems governing physiological and motor responses under threat. We argue for an integrative framework where defensive responses and motor preparation are driven by motivational relevance, which escalates with perceived imminence, harm potential, and escape possibility. These findings underscore the interconnected nature of affective and motor processes, offering new perspectives on human defensive behavior.

When confronted by predators, animals make innate decisions with rapid reaction times—a trait shaped by natural selection to maximize survival. However, rapid reactions are effective only when grounded in accurate judgments and appropriate choices, which often require cognitive control. To address how such choices are shaped, we developed a behavioral paradigm to investigate how threat intensity, reward value, and social hierarchy influence decision-making in foraging mice exposed to overhead visual threats. Using a machine learning-based approach, we classified defensive responses into four distinct decision types. We observed rapid habituation to repeated looming threats, with substantial inter-individual variability in the rate of habituation. Across both early and late phases of habituation, threat intensity is the primary determinant of decision-making, strongly driving behavior towards escape. In contrast, the influence of reward is context-dependent and emerges primarily in the late phase: under low-threat conditions, higher rewards suppress defensive responses, consistent with value-based decision theory, whereas under high-threat conditions, higher rewards promote escape, potentially reflecting heightened vigilance. Innate decision-making is further modulated by social hierarchy, with dominant mice showing greater vigilance and a stronger bias towards risk-averse behaviors, while subordinates are more reward-driven. To understand the underlying decision-making process, we developed a drift-diffusion leaky integrator model that successfully captures how threat intensity, reward value, and vigilance are integrated. Together, these findings reveal the economic and social modulation of innate decisions, offering insights into the computational mechanisms underlying the interplay between instinctive reactions and cognitive control.

When confronted by predators, animals make innate decisions with rapid reaction times—a trait shaped by natural selection to maximize survival. However, rapid reactions are effective only when grounded in accurate judgments and appropriate choices, which often require cognitive control. To address how such choices are shaped, we developed a behavioral paradigm to investigate how threat intensity, reward value, and social hierarchy influence decision-making in foraging mice exposed to overhead visual threats. Using a machine learning-based approach, we classified defensive responses into four distinct decision types. We observed rapid habituation to repeated looming threats, with substantial inter-individual variability in the rate of habituation. Across both early and late phases of habituation, threat intensity is the primary determinant of decision-making, strongly driving behavior towards escape. In contrast, the influence of reward is context-dependent and emerges primarily in the late phase: under low-threat conditions, higher rewards suppress defensive responses, consistent with value-based decision theory, whereas under high-threat conditions, higher rewards promote escape, potentially reflecting heightened vigilance. Innate decision-making is further modulated by social hierarchy, with dominant mice showing greater vigilance and a stronger bias towards risk-averse behaviors, while subordinates are more reward-driven. To understand the underlying decision-making process, we developed a drift-diffusion leaky integrator model that successfully captures how threat intensity, reward value, and vigilance are integrated. Together, these findings reveal the economic and social modulation of innate decisions, offering insights into the computational mechanisms underlying the interplay between instinctive reactions and cognitive control.

When confronted by predators, animals make innate decisions with rapid reaction times—a trait shaped by natural selection to maximize survival. However, rapid reactions are effective only when grounded in accurate judgments and appropriate choices, which often require cognitive control. To address how such choices are shaped, we developed a behavioral paradigm to investigate how threat intensity, reward value, and social hierarchy influence decision-making in foraging mice exposed to overhead visual threats. Using a machine learning-based approach, we classified defensive responses into four distinct decision types. We observed rapid habituation to repeated looming threats, with substantial inter-individual variability in the rate of habituation. Across both early and late phases of habituation, threat intensity is the primary determinant of decision-making, strongly driving behavior towards escape. In contrast, the influence of reward is context-dependent and emerges primarily in the late phase: under low-threat conditions, higher rewards suppress defensive responses, consistent with value-based decision theory, whereas under high-threat conditions, higher rewards promote escape, potentially reflecting heightened vigilance. Innate decision-making is further modulated by social hierarchy, with dominant mice showing greater vigilance and a stronger bias towards risk-averse behaviors, while subordinates are more reward-driven. To understand the underlying decision-making process, we developed a drift-diffusion leaky integrator model that successfully captures how threat intensity, reward value, and vigilance are integrated. Together, these findings reveal the economic and social modulation of innate decisions, offering insights into the computational mechanisms underlying the interplay between instinctive reactions and cognitive control.