Individual Variation In Behaviour Research Articles

Exploratory behavior is linked to stress physiology and social network centrality in free-living house finches (Haemorhous mexicanus)

Animal personality has been linked to individual variation in both stress physiology and social behaviors, but few studies have simultaneously examined covariation between personality traits, stress hormone levels, and behaviors in free-living animals. We investigated relationships between exploratory behavior (one aspect of animal personality), stress physiology, and social and foraging behaviors in wild house finches (Haemorhous mexicanus). We conducted novel environment assays after collecting samples of baseline and stress-induced plasma corticosterone concentrations from a subset of house finches. We then fitted individuals with Passive Integrated Transponder tags and monitored feeder use and social interactions at radio-frequency identification equipped bird feeders. First, we found that individuals with higher baseline corticosterone concentrations exhibit more exploratory behaviors in a novel environment. Second, more exploratory individuals interacted with more unique conspecifics in the wild, though this result was stronger for female than for male house finches. Third, individuals that were quick to begin exploring interacted more frequently with conspecifics than slow-exploring individuals. Finally, exploratory behaviors were unrelated to foraging behaviors, including the amount of time spent on bird feeders, a behavior previously shown to be predictive of acquiring a bacterial disease that causes annual epidemics in house finches. Overall, our results indicate that individual differences in exploratory behavior are linked to variation in both stress physiology and social network traits in free-living house finches. Such covariation has important implications for house finch ecology, as both traits can contribute to fitness in the wild.

Physiological stress responses in wild Asian elephants Elephas maximus in a human-dominated landscape in the Western Ghats, southern India

Increasing anthropogenic pressures on forests, especially in the tropical regions of the world, have restricted several large mammalian species such as the Asian elephant to fragmented habitats within human-dominated landscapes. In this study, we assessed the effects of an anthropogenic landscape and its associated conflict with humans on the physiological stress responses displayed by Asian elephants in the Anamalai Hills of the Western Ghats mountains in south India. We have quantified faecal glucocorticoid metabolite (FGM) concentrations in focal individual elephants within and across herds, inhabiting both anthropogenic and natural habitats, and evaluated their physiological responses to different socio-ecological situations between November 2013 and April 2014. Physiological stress responses varied significantly among the tested elephant age- and sex categories but not across different types of social organisation. Adults generally showed higher FGM concentrations, even in the absence of stressors, than did any other age category. Males also appeared to have higher stress responses than did females. Although there was no significant variation in mean stress levels between elephants on the plateau in the absence of human interactions and those in adjacent, relatively undisturbed forest habitats, FGM concentrations increased significantly for adult and subadult individuals as well as for calves following drives, during which elephants were driven off aggressively by people. Our study emphasises the general importance of understanding individual variation in physiology and behaviour within a population of a seriously threatened mammalian species, the Asian elephant, and specifically highlights the need for long-term monitoring of the stress physiology and behavioural responses of individual elephants across both human-dominated and natural landscapes. Such studies would not only provide comprehensive insights into the adaptive biology of elephants in changing ecological regimes but also aid in the development of effective management and conservation strategies for endangered populations of the species.

S172. Characterizing Individual Variation in Multi-Modal Thalamic Connectivity and Behavior

S172. Characterizing Individual Variation in Multi-Modal Thalamic Connectivity and Behavior

Plasticity in extended phenotype increases offspring defence despite individual variation in web structure and behaviour

Many animals actively defend their offspring using a range of behaviours from calling and mobbing in birds, to physical grappling in crustaceans, and the expression of these behaviours positively scale with offspring value. While this role of behaviour in defence is well studied, very little is known about how other traits, specifically the structure of architectural constructions such as webs and nests, contribute to offspring defence. Additionally, although some tax a show consistent individual differences in offspring defence behaviour, it is completely unknown whether individuals also differ in defensive structures. We addressed these questions in the redback spider, Latrodectus hasselti, by measuring how a female laying an eggcase influences female behaviour and web structure, and whether those traits scale with relative reproductive investment. Our results show that females modified web structure in response to an eggcase, but only the protective elements of web structure positively scaled with the relative value of that eggcase. Finally, despite the significant correlations, fixed effects (e.g. eggcase possession/value) in the models explained only 5–23% of the variation in behaviour and web structure, while the random effect of individual identity explained 46–65% of the variation. This variation drove moderate to high repeatability estimates across all traits, suggesting that some individuals consistently invest relatively more in defence, while some invest less. These results highlight that extended phenotypic traits may be a critical component of offspring defence in some taxa. Furthermore, individual variation in these traits suggest that different reproductive strategies may exist, whereby some individuals invest more in reproduction at a cost to safety/foraging and vice versa.

Meta-analysis reveals weak associations between intrinsic state and personality.

Individual differences in behaviour characterize humans and animals alike. A hot field in behavioural ecology asks why this variation in 'personality' evolved. Theory posits that selection favours the integration of 'intrinsic state' and behaviour. Metabolism, hormones, energetic reserves and structural size have particularly been proposed as states covarying with behaviour among-individuals, either genetically or through plasticity integration. We conducted a meta-analysis estimating the amount of among-individual variation in behaviour attributable to variation in state. Our literature search showed that only 22% of the studies claiming to estimate individual-level associations between state and behaviour actually did so. Our meta-analysis revealed that relatively aggressive, bold, explorative and/or active individuals had relatively high metabolic rates, hormone levels, body weights and/or body sizes. The proportion of among-individual variation common to state and behaviour was nevertheless small (approx. 5%). This means that (i) adaptive explanations involving intrinsic states fail to explain much individual variation in behaviour, (ii) empiricists should consider nonlinear, additive or interactive effects of (multiple) intrinsic states, (iii) explanations not involving intrinsic states might be important, or (iv) empirical tests of state-dependent personality theory were inappropriate. Our meta-analysis highlights the importance of feedback between empiricists and theoreticians in the study of adaptive behavioural variation.

AI personalities: clues from animal research

ABSTRACTThe existence of individual behavioural variation within and among animal populations has become a popular topic of investigation in behavioural ecology. So far, research has revealed the complexity of the phenomenon, and how much there is left to learn about its underlying causes, and potential consequences. Yet, behavioural variation among individuals need not be constrained to the animal kingdom. Animal personality, and the lessons we have learned about it, could apply to other fields of inquiry as well. Interestingly, these fields do not have to be constrained to biology. Here, the hidden parallels between animal personality and the ongoing efforts to develop artifical general intelligence will be identified. This points towards a neglected aspect in the consideration of potential effects artificial general intelligence (AGI) may have: it could have a ‘personality’.

Oxygen consumption and swimming performance in Arctic charr with different pigmentation patterns

Pigmentation in animals often reflects behavioural and physiological traits, such as health status, stress responsiveness, and dominance. Individual variation in stress response and behaviour has earlier been proposed to be connected to differences in metabolism. The aim of this study was to investigate the connection between pigmentation, behaviour, and oxygen consumption in Arctic charr (Salvelinus alpinus). In this species, we have earlier found an association between number of carotenoid spots on the skin and physiological response to stress (stress coping style). Swimming endurance and respiration rates were estimated from video recorded behaviour and oxygen consumption in a swim tunnel. Flow velocity was kept as 1.6 BL (body lengths) s−2 for 60 min, and oxygen consumption (mg min−1 g−1) during that time was used as a proxy for metabolism. Oxygen consumption was negatively correlated with number of spots. Also behaviour scores from a principal component analysis varied with pigmentation, with a negative correlation between number of spots and behaviour scores connected with endurance. Fish with fewer spots rested more against the rear of the chamber, and fish with more spots were sooner, and more often, pressed to the rear grid by the water current. The variation in oxygen consumption in the swim tunnel indicates a relation between respiration rate, swimming endurance, and pigmentation in the Arctic charr. With earlier findings on covariations between spot numbers and stress coping in this species, there seems to be connections between stress coping style, behaviour, and metabolism. Thus, it would be possible to identify individual expression of these features, based on the pigmentation patterns of the fish.

The Utility of Animal Behavior Studies in Natural Resource Management

On the Ground • Although research on the behavior of individual animals has been growing in recent years, the role that individual variation among animals may play in the outcome of species interactions in nature may be somewhat overlooked in natural resource management. Recognizing potential implications of individual behavioral variation can aid in developing more cost-effective and sustainable management techniques. Four illustrative examples are provided. • Livestock foraging behaviors are important to understand, as they affect an animal'’s ability to locate and identify forage with nutritional qualities required for optimal growth. Studying the behavior of individual animals can help livestock producers anticipate and influence livestock grazing patterns to increase efficiency and productivity. • Sage-grouse populations have declined dramatically in many areas, and managers are required to consider their needs in all management decisions where the species persists. Sage-grouse exhibit complex mating, nesting, and migratory behaviors that are important to recognize for management to be successful. • Mountain lions were generally assumed to prey mainly upon mule deer, but recent studies have found that individual lions may specialize on alternate prey such as feral horses or bighorn sheep. The Bureau of Land Management spends millions of dollars each year to manage feral horse populations. Revelations surrounding prey switching in individual mountain lions may support management goals in which feral horse predation is occurring but may hinder bighorn sheep translocation efforts by wildlife managers. • Many plants important to land managers, including grasses, shrubs, and trees, are dispersed by granivorous rodents that store seeds in scattered caches, and a growing body of literature reveals that the majority of seedling recruitment for some of these species is attributable to scatter-hoarding by rodents. This relationship can be utilized for restoration applications, and variation in seed preferences among individual animals may be valuable in this regard.

Examination of Clock and Adcyap1 gene variation in a neotropical migratory passerine.

Complex behavioral traits, such as those making up a migratory phenotype, are regulated by multiple environmental factors and multiple genes. We investigated possible relationships between microsatellite variation at two candidate genes implicated in the control of migratory behavior, Clock and Adcyap1, and several aspects of migratory life-history and evolutionary divergence in the Painted Bunting (Passerina ciris), a species that shows wide variation in migratory and molting strategies across a disjunct distribution. We focused on Clock and Adcyap1 microsatellite variation across three Painted Bunting populations in Oklahoma, Louisiana, and North Carolina, and for the Oklahoma breeding population we used published migration tracking data on adult males to explore phenotypic variation in individual migratory behavior. We found no correlation between microsatellite allele size within either Clock and Adcyap1 relative to the initiation or duration of fall migration in adult males breeding in Oklahoma. We also show the lack of significant correlations with aspects of the migratory phenotype for the Louisiana population. Our research highlights the limitations of studying microsatellite allelic mutations that are of undetermined functional influence relative to complex behavioral phenotypes.

Individual variation in reproductive behaviour is linked to temporal heterogeneity in predation risk.

Variation in predation risk is a major driver of ecological and evolutionary change, and, in turn, of geographical variation in behaviour. While predation risk is rarely constant in natural populations, the extent to which variation in predation risk shapes individual behaviour in wild populations remains unclear. Here, we investigated individual differences in reproductive behaviour in 16 Trinidadian guppy populations and related it to the observed variation in predator biomass each population experienced. Our results show that high heterogeneity in predator biomass is linked to individual behavioural diversification. Increased within-population heterogeneity in predator biomass is also associated with behavioural polymorphism. Some individuals adjust the frequency of consensual mating behaviour in response to differences in sex ratio context, while others display constantly at elevated frequencies. This pattern is analogous to a 'live fast, die young' pace-of-life syndrome. Notably, both high and low mean differences in predator biomass led to a homogenization of individual frequency of consensual mating displays. Overall, our results demonstrate that individual behavioural variation is associated with heterogeneity in predator biomass, but not necessarily with changes in mean values of predator biomass. We suggest that heterogeneity in predator biomass is an informative predictor of adaptive responses to changes in biotic conditions.

Plasticity and personality of parental care in the clown anemonefish

Characterizing individual variation in parental care is critical to understanding how selection shapes and maintains patterns of care, yet little is known about how individual parents vary in their responses to the environment. Reaction norms, functions that describe how phenotypes change across an environmental gradient, provide an elegant framework for studying individual variation in behavioural responses. We use a reaction norm approach to investigate how studying plasticity, which describes variation within an individual through time, and personality, which describes repeatable variation among individuals, together explain individual variation in the parental behaviour of the anemonefish Amphiprion percula. More specifically, we test how resource availability influences individual parental responses to the environment and discuss the consequences for our understanding of plasticity and personality in parental care. Breeding pairs of A. percula were fed either a high or a low food ration and their parental behaviours were monitored. Individuals exhibited plasticity in parental behaviour across the two resource environments. Furthermore, individuals were repeatable in their behaviour through time, as evidenced by significant among-individual variation in intercept. Finally, the slope and elevation of individual reaction norms varied, revealing a level of variation not captured at the population level and providing insight into the potential mechanisms generating individual variation.

The number of neurons in specific amygdala regions is associated with boldness in mink: a study in animal personality.

Conspecifics vary consistently in their behavioural responses towards environment stimuli such as exposure to novel objects; ethologists often refer to this variability as animal personality. The neurological mechanisms underlying animal personality traits remain largely unknown, but linking the individual variation in emotional expression to brain structural and neurochemical factors is attracting renewed interest. While considerable research has focused on hormonal and neurotransmitter effects on behavioural responses, less is known about how individual variation in the number of specific neuron populations contributes to individual variation in behaviour. The basolateral amygdala (BLA) and the central nuclei of the amygdala (CeA) mediate emotional processing by regulating behavioural responses of animals in a potentially threatening situation. As such, these structures are good candidates for evaluating the relationship between neuronal populations and behavioural traits. We now show that individual American mink (Neovison vison) reacting more boldly towards novelty have more neurons in the BLA than do their more timid conspecifics, suggesting that a developmental pattern of the number of amygdala neurons can influence behavioural traits of an adult animal. Furthermore, post hoc correlations revealed that individuals performing with higher arousal, as reflected by their frequency of startle behaviour, have more CeA neurons. Our results support a direct link between the number of neurons in amygdala regions and aspects of animal personality.

Underlying mechanisms and ecological context of variation in exploratory behavior of the Argentine ant, Linepithema humile.

Uncovering how and why animals explore their environment is fundamental for understanding population dynamics, the spread of invasive species, species interactions, etc. In social animals, individuals within a group can vary in their exploratory behavior, and the behavioral composition of the group can determine its collective success. Workers of the invasive Argentine ant (Linepithema humile) exhibit individual variation in exploratory behavior, which affects the colony's collective nest selection behavior. Here, we examine the mechanisms underlying this behavioral variation in exploratory behavior and determine its implications for the ecology of this species. We first establish that individual variation in exploratory behavior is repeatable and consistent across situations. We then show a relationship between exploratory behavior and the expression of genes that have been previously linked with other behaviors in social insects. Specifically, we found a negative relationship between exploratory behavior and the expression of the foraging (Lhfor) gene. Finally, we determine how colonies allocate exploratory individuals in natural conditions. We found that ants from inside the nest are the least exploratory individuals, whereas workers on newly formed foraging trails are the most exploratory individuals. Furthermore, we found temporal differences throughout the year: in early-mid spring, when new resources emerge, workers are more exploratory than at the end of winter, potentially allowing the colony to find and exploit new resources. These findings reveal the importance of individual variation in behavior for the ecology of social animals.

Advances from the nexus of animal behaviour and pathogen transmission: new directions and opportunities using contact networks

AbstractContact network models have enabled significant advances in understanding the influence of behaviour on parasite and pathogen transmission. They are an important tool that links variation in individual behaviour, to epidemiological consequences at the population level. Here, in our introduction to this special issue, we highlight the importance of applying network approaches to disease ecological and epidemiological questions, and how this has provided a much deeper understanding of these research areas. Recent advances in tracking host behaviour (bio-logging: e.g., GPS tracking, barcoding) and tracking pathogens (high-resolution sequencing), as well as methodological advances (multi-layer networks, computational techniques) started producing exciting new insights into disease transmission through contact networks. We discuss some of the exciting directions that the field is taking, some of the challenges, and importantly the opportunities that lie ahead. For instance, we suggest to integrate multiple transmission pathways, multiple pathogens, and in some systems, multiple host species, into the next generation of network models. Corresponding opportunities exist in utilising molecular techniques, such as high-resolution sequencing, to establish causality in network connectivity and disease outcomes. Such novel developments and the continued integration of network tools offers a more complete understanding of pathogen transmission processes, their underlying mechanisms and their evolutionary consequences.

Rainbow trout personality: individual behavioural variation in juvenile Oncorhynchus mykiss

Abstract We evaluated the variation in dispersal, exploration, and aggression across time in juvenile progeny produced from wild caught rainbow trout (Oncorhynchus mykiss) at a critical developmental shift associated with the highest mortality in fish. By testing multiple ecologically relevant behaviours repeatedly in the same individuals, we simultaneously tested multiple hypotheses regarding personality, plasticity, and behavioural syndromes to better understand the innate behavioural variation in a population containing both migratory and resident life histories. There were consistent behavioural differences, or personality, between individuals across time, for dispersal, aggression, and exploration, unrelated to size or sex. The significant repeatabilities (0.10–0.46) indicate that these traits are potentially heritable. Also, we found both habituation in all behaviours and significant differences between individuals in the rate of that habituation, despite no evidence of a behavioural syndrome. The identification of this individual level variation is a step towards understanding which heritable traits selection could influence.

Modeling Individual Cyclic Variation in Human Behavior.

Cycles are fundamental to human health and behavior. Examples include mood cycles, circadian rhythms, and the menstrual cycle. However, modeling cycles in time series data is challenging because in most cases the cycles are not labeled or directly observed and need to be inferred from multidimensional measurements taken over time. Here, we present Cyclic Hidden Markov Models (CyH-MMs) for detecting and modeling cycles in a collection of multidimensional heterogeneous time series data. In contrast to previous cycle modeling methods, CyHMMs deal with a number of challenges encountered in modeling real-world cycles: they can model multivariate data with both discrete and continuous dimensions; they explicitly model and are robust to missing data; and they can share information across individuals to accommodate variation both within and between individual time series.Experiments on synthetic and real-world health-tracking data demonstrate that CyHMMs infer cycle lengths more accurately than existing methods, with 58% lower error on simulated data and 63% lower error on real-world data compared to the best-performing baseline. CyHMMs can also perform functions which baselines cannot: they can model the progression of individual features/symptoms over the course of the cycle, identify the most variable features, and cluster individual time series into groups with distinct characteristics. Applying CyHMMs to two real-world health-tracking datasets—of human menstrual cycle symptoms and physical activity tracking data—yields important insights including which symptoms to expect at each point during the cycle. We also find that people fall into several groups with distinct cycle patterns, and that these groups differ along dimensions not provided to the model. For example, by modeling missing data in the menstrual cycles dataset, we are able to discover a medically relevant group of birth control users even though information on birth control is not given to the model.

Proceedings of the 10th International Symposium on the Nutrition of Herbivores

Interest and limits of two methods to characterize the individual variability in feeding behaviour of barn-dried hay measured continuously in dairy goats. 10th International Symposium on the Nutrition of Herbivores

Transient inactivation of the paraventricular nucleus of the thalamus enhances cue-induced reinstatement in goal-trackers, but not sign-trackers.

The paraventricular nucleus of the thalamus (PVT) has been shown to mediate cue-motivated behaviors, such as sign- and goal-tracking, as well as reinstatement of drug-seeking behavior. However, the role of the PVT in mediating individual variation in cue-induced drug-seeking behavior remains unknown. This study aimed to determine if inactivation of the PVT differentially mediates cue-induced drug-seeking behavior in sign-trackers and goal-trackers. Rats were characterized as sign-trackers (STs) or goal-trackers (GTs) based on their Pavlovian conditioned approach behavior. Rats were then exposed to 15days of cocaine self-administration, followed by a 2-week forced abstinence period and then extinction training. Rats then underwent tests for cue-induced reinstatement and general locomotor activity, prior to which they received an infusion of either saline (control) or baclofen/muscimol (B/M) to inactivate the PVT. Relative to control animals of the same phenotype, GTs show a robust increase in cue-induced drug-seeking behavior following PVT inactivation, whereas the behavior of STs was not affected. PVT inactivation did not affect locomotor activity in either phenotype. In GTs, the PVT appears to inhibit the expression of drug-seeking, presumably by attenuating the incentive value of the drug cue. Thus, inactivation of the PVT releases this inhibition in GTs, resulting in an increase in cue-induced drug-seeking behavior. PVT inactivation did not affect cue-induced drug-seeking behavior in STs, suggesting that the role of the PVT in encoding the incentive motivational value of drug cues differs between STs and GTs.

Consistent individual variation across interaction networks indicates social personalities in lemurs

Group members interact with each other during multiple social behaviours that range from aggressive to affiliative interactions. It is not known, however, whether an individual's suite of social behaviours consistently covaries through time and across different types of social interactions. Consistent social behaviour would be advantageous in groups, especially when individuals need to remember their group members' social roles and preferences in order to keep track of social relationships and predict conspecifics' future behaviour. Here, we address whether social behaviour of ringtailed lemurs, Lemur catta, is consistent through time and across four interaction networks (aggression, grooming, contact calling, scent marking). We quantified variation in social behaviour through four network centrality measures including outdegree, outstrength, betweenness and eigenvector centrality. Comparing lemurs' measures across 2 years revealed that network centrality remained consistent between years. Lemurs' centrality also stayed consistent across interaction networks: individuals with high centrality in one interaction network also had high centrality in the other networks, even when we controlled for sex-based variation in social behaviour. Thus, regardless of their sex, some individuals were highly social and frequently groomed others, initiated aggressive interactions and responded to others' contact calls and scent marks. Lemurs also had preferred social partners they frequently interacted with across years and across multiple behaviours. In particular, lemurs frequently responded to the contact calls and the scent marks of the conspecifics they had frequently groomed. Together, these results demonstrate that individual variation in lemur social behaviour is not context specific, but instead persists through time and across multiple social interactions. Such consistent behaviour provides evidence of social personalities, which may influence individuals' interaction styles, including how socially active they are and with whom they interact.

Virtual fencing of cattle using an automated collar in a feed attractant trial

Managing grazing cattle can be challenging in environmentally-sensitive areas or when there is limited contact with and control over the animals. Virtual fences – barriers without a physical barrier – represent the potential for animal guidance in locations where physical fences may be unfeasible. In this study automated collars that provided audio and electrical stimuli to cattle were tested on 12 naïve heifers to determine if cattle could be deterred from a feed attractant in a series of 3 test paddocks. All animals were individually trained (no virtual fence line set) across 3days (each paddock once per day) to walk unrestricted down to a bale of hay. The heifers were then each fitted with the experimental prototype collar device and a virtual fence line was set across the width of each paddock to restrict animals from the hay reward. As the animal approached the virtual fence line the collar emitted a 2.5s audio cue (785Hz±15Hz, 58DB). If the animal stopped or turned away no further cues were emitted, if the animal continued forward an electrical stimulus (800V electrical pulses delivered in less than 1s) was applied immediately following the audio cue. The audio-electrical stimulus sequence was repeated as animals continued into the exclusion zone (where the hay was located). Each animal was tested in each paddock across 3days reaching a total of 8 trials when animals were no longer voluntarily approaching the hay. Logistic regression analyses showed a mean number of 6 interactions with the fence line until 50% of animals were learning to avoid the fence line based on the audio cue. The odds ratio of 1.28 (95% CI 1.14–1.44) showed that with each fence interaction, animals were 28% more likely to appropriately respond to the audio cue and avoid the electrical stimulus (Likelihood Ratio Test χ2=21.51, DF=1, P<0.0001). However, there was high variation between individual animals in their rate of learning and the behaviours they exhibited in response to both the audio and electrical stimuli. The automated collars were able to successfully exclude the majority of animals from accessing the hay but further research should aim to assess the impacts of group dynamics on individual behavioural variation and how aspects of temperament or cognition may influence learning of a virtual fencing system.