Consistent Individual Differences In Behaviour Research Articles

Bold rats (Niviventer confucianus) are more effective in seed dispersal: evidence both under enclosure conditions and in the field.

Rodents are important seed dispersers of plants because they move seeds far away from the parent trees and hoard seeds in the soil, benefiting seed dispersal and regeneration. Traits of plant seeds and animals are associated with rodent-mediated seed dispersal, but animal personality, the consistent individual behavioral differences in time and environments, has not been fully considered. Here, we first measured the personality of 26 Niviventer confucianus in the laboratory, and 10 individuals in the field of one population, and then tested their behavior of seed consumption and hoarding both in semi-natural enclosures and the field. We tested the hypothesis that individuals with different personalities have different preferences for seed consumption and hoarding, which has different implications for seed dispersal and regeneration. Under the enclosure conditions, all parameters of personality are repeatable; bold individuals harvested fewer seeds but scatter-hoarded more seeds and dispersed farther than timid ones, whereas active individuals consumed more seeds, but left fewer seeds on the ground surface than inactive ones. In the field, boldness, activity, and exploration of the animals are repeatable; bold individuals scatter-hoarded more seeds to farther distances than timid ones, whereas active individuals harvested and consumed more seeds than inactive ones. These results suggest that bold rats tended to scatter hoard seeds and disperse them to a longer distance, implying they are more effective in seed dispersal. In the future, animal personality (e.g. boldness and activity) should be considered in seed dispersal studies and ecological-based manipulation in seed dispersal and regeneration of forests.

Aggressive behavior as a predictor of home range size: findings from both range-restricted and widespread Darwin’s finch species

AbstractInformation about an animal’s home range (the geographical area in which it accesses resources for survival and reproduction) is vital broadly for understanding animal behavior and specifically for developing conservation management plans. Although personality traits—consistent individual differences in behavior across time and contexts—may affect an animal’s home range size, we still lack a breadth of empirical studies across systems to fully appreciate this influence. Here, we tested the relationship between behavioral responses and home range size in two Darwin’s finch species on Floreana Island: the critically endangered and range-restricted Medium Tree Finch (Camarhynchus pauper) and the common and widespread Small Ground Finch (Geospiza fuliginosa). Using a combination of rapid-assessment assays during both short-term captivity and in the field, we measured exploration and aggressiveness in males from both species. We then used radio telemetry to measure each bird’s home range size over a week-long period. We predicted that (1) fast-exploring individuals would have larger home ranges, and (2) more aggressive individuals would have smaller home ranges. We found that Medium Tree Finches had smaller home ranges than Small Ground Finches, that exploratory behavior was positively correlated with home range size only in Small Ground Finches, and that, in both species, individuals’ aggressiveness was negatively correlated with home range size, whereby the more aggressive individuals occupied smaller home ranges. We conclude that behavioral responses that align with major personality traits can predict home range size, which may provide an important tool for the conservation and management of endangered species when, for example, selecting individuals with different personality profiles for reintroduction.

Consistent individual differences in behavior among beef cattle in handling contexts and social-feed preference testing

Consistent individual differences (CIDs) in animal behavior, also known as personality or temperament, are measured in a variety of assays and are presumed to represent relatively stable traits of individual animals. Because these behaviors are presumed to represent stable traits, repetition of assays over short and long-term time frames and contexts is crucial; such repetitions are not commonly achieved in literature regarding the topic of CIDs, especially not in a singular study. In beef cattle, CIDs are often related to feeding and social preferences, which is relevant for extensively managed herds of ruminants. This study investigated the consistency of behavior among 50 breeding Angus x Hereford cows across repetitions within one year and over one year during three distinct contexts: handling and isolation in a chute corral system, choice in a social-feed tradeoff test, and response in a novel bucket approach test. We found that cows were consistent across short-term (assessed with repeatabilities [R]) and long-term (assessed with correlations across multivariate models [r]) timeframes in durations of behaviors exhibited in the management context (e.g. while handled [R = 0.60, r = 0.39], while traversing a cement chute [R = 0.69, r = 0.67] and an open squeeze stall [R = 0.76, r = 0.85]). Repeatable behaviors from the handling and isolation in chute system context were input into PCA with varimax rotation. Behaviors loaded onto three principal components that explained 66 % of the variance in the data and distinguished cows along axes of activity, fearfulness and excitability. Cows that were deemed less active (p = 0.010) and less excitable (p = 0.039) chose to approach the supplement bucket over gaining proximity to conspecifics in a social-feed tradeoff test. Even though the cows were not restrained in a squeeze stall, consistent individual differences in behavior across short (within year) and long-term (between years) timeframes were found. This suggests that future research can use unrestrained methods to evaluate cattle temperament, which could improve animal welfare and safety of handlers during experiments. Passive and less excitable beef cattle were more feed-centric, indicating that CIDs in behavior assays could potentially be used to predict feeding behavior because of an underlying stable trait in cows that ties response to handling and management with feed choice in a social-feed tradeoff task.

Individual behavioural variation does not affect social organization or reproductive success in a cooperative small mammal

Abstract Recent evidence indicates that individual behavioural variation in animals, defined as consistent individual differences in behaviour across contexts and time, influence ecological and evolutionary processes, and a growing number of studies demonstrate that individual behavioural variation can play a large role in shaping grouping dynamics among social animals. We studied the common degu, Octodon degus, a social rodent, to evaluate whether individual behavioural variation underlies social organization and the reproductive success of individuals within groups. We examined social groups in a population in central-north Chile during one breeding season, tested 67 adults in an open field test (i.e., the propensity to explore an unfamiliar environment) and 62 adults in a poke test (i.e., the propensity to charge an object) to quantify individual behavioural variation, determined assortment based on individual behavioural differences across 19 social groups, and performed genetic analyses to assess reproductive success. We found that the response to the poke test was repeatable, while none of the behaviours from an open field test were. The repeatable behaviour during the poke test was not associated to components of social organization (group composition), or to reproductive success. These findings imply that individual behavioural variation did not affect grouping patterns or direct fitness in this degu population.

When slow explorers are fast: Personality‐related differences in timing of migration in Red Knots (Calidris canutus)

The timing of migration varies significantly among individuals, even within populations sharing breeding sites. Consistent individual behavioural differences, known as personality traits, have been linked to variation in movement behaviour. However, little attention has been given to investigating whether personality traits can explain such variation in the timing of migration. We studied post‐breeding migration of Red Knots Calidris canutus islandica breeding in the High Arctic and wintering in European coastal areas. We captured Red Knots in the Dutch Wadden Sea, a main non‐breeding and moulting site, and assessed their exploration behaviour, a personality trait, before releasing them with colour‐rings. We first investigated whether arrival timing in marine areas was associated with exploration speed. Secondly, we asked whether slow explorers were more likely to fly non‐stop to the Wadden Sea compared with fast explorers, as faster explorers were expected to move more and visit more staging sites. To determine arrival timing in marine non‐breeding areas and non‐stop flights to the Wadden Sea, we analysed isotope signatures in blood samples collected after capture, as these differ between the terrestrial breeding grounds (arthropod diet) and marine non‐breeding and moulting sites (benthic invertebrate diet). Thirdly, we estimated arrival time in the Wadden Sea based on primary moult progress, allowing us to examine the relationship between arrival timing estimated from isotope values and the onset of moult. Our findings revealed that slower exploring Red Knots departed earlier from the breeding site and were more likely to fly non‐stop to the Wadden Sea than were faster exploring individuals. Arrival timing to marine areas as estimated from isotope analyses predicted arrival timing in the Wadden Sea (via moult progress) but this relationship exhibited significant variation, possibly due to individual differences in the use of staging sites en route. By migrating early, slower explorers can better outpace the aerial predators also arriving at the Wadden Sea moulting site and thereby reduce mortality risk due to predation.

Complexities of consistent individual behavioral differences in effective wildlife management

Complexities of consistent individual behavioral differences in effective wildlife management

Development of "personality" in the domestic cat: A longitudinal study.

Although individual differences in the behavior of animals, sometimes referred to as personality, have recently received considerable attention, the development of such differences remains understudied. We previously found consistent individual differences in behavior in four tests simulating everyday contexts in 74 preweaning age kittens from 16 litters of the domestic cat. To study the development of consistent among-individual differences in four behavioral traits in cats, we followed a subset of these same individuals and repeated the same tests at 6 and 12 months of age. Some individual differences in behavior became increasingly repeatable with age due to a combination of decreased individual-level variance (canalization) and increased among-individual variance; these changes in variance and repeatability continued into adulthood (12 months). We did not observe behavioral syndromes at any age, in contrast to our previous reports in a different population of adult cats. The mechanisms that underlie increased repeatability with age and the possibility of personality structure differing between populations in this species remain to be studied.

Avian malaria parasite infections do not affect personality in the chestnut thrush (Turdus rubrocanus) on the Qinghai-Tibet Plateau

Personality traits, the consistent individual behavioral differences, are currently gaining much attention in studies of natural bird populations. However, associations between personality traits and parasite infections are not often investigated. Even less attention has been given to studies of birds in the high-elevation region such as the Tibetan plateau. This research aims to examine the relationship between avian malaria parasites and two personality traits in a population of the Chestnut Thrush (Turdus rubrocanus) breed in the Tibetan plateau.Our results revealed no evidence of sex bias in malaria parasite prevalence. Furthermore, we found no effect of infection status on two personality scores: activity and boldness. Additionally, no effects on the activity level or boldness were observed for different parasite lineages of Haemoproteus, Leucocytozoon, the sex of the birds, or their interactions. Similarly, we did not find any relationship between activity level and boldness with nestling numbers, sex, or their interactions. Notably, individuals with a larger number of offspring tended to display greater boldness. Our findings indicate that blood parasite infections are common in this population but do not significantly impact the personality of the birds.

Responses to environmental enrichment are associated with personality characteristics in chestnut-bellied seed finches (Sporophila angolensis)

Environmental enrichment (EE) is used to promote natural behaviours in captive animals and may hold promise as a form of pre-release training, a strategy for improving coping skills of translocated birds. We investigated the use of EE to enhance foraging and vigilance behaviours of captive Sporophila angolensis, which may be related to post-release survival. We also evaluated whether consistent individual behavioural differences affected birds’ responses to EE. We submitted 19 captive seed-finches to three short-term challenges: tonic immobility (TI), new environment (NE) and new object (NO) tests. TI behaviour is related to fear/escape response to potential predators and novelty tests (NE and NO) assess neophobia, which are ecologically relevant personality traits influencing the shyness-boldness continuum. We noted a pronounced variability among the individuals’ personality traits, both in their fear and escape-related responses in the TI test and along shy/bold z-scores in NE and NO tests. During a period of enrichment, birds spent more time foraging and less time in vigilance states compared with both control phases. Personality traits of the birds affected their responses to enrichment with bolder birds spending more time foraging. The EE-related decrease in vigilance was independent of the birds’ personality traits. Our findings highlight interactions between personality and rearing environment that may impact post-release outcomes for translocated animals.

Sex-Specific Effects of Blood Serotonin on Reproductive Effort in a Small Passerine.

AbstractLaboratory animal models have shown that blood serotonin levels reflect consistent individual differences in behavioral decision-making and maternal behavior. Serotonin could also help to understand intraspecific variation in reproductive strategies, although the mechanisms are poorly understood. In this study, the relationships of plasma serotonin with breeding parameters and parental behavior were examined in wild great tits (Parus major). Females who laid eggs earlier had higher levels of serotonin in the second half of the nestling period, while no significant relationship of serotonin with clutch size, brood size, and body size was detected. In males, serotonin levels were negatively related to clutch size and brood size and positively related to body size. The association of serotonin with provisioning behavior was sex specific, and acute fear stress induced by a predator presentation did not change this relationship. Food provisioning was positively related to size-corrected serotonin levels in females and negatively related to size-corrected serotonin levels in males. These results suggest that peripheral serotonin is a sensitive marker of parental behavior and reproductive effort in wild birds, while the mechanisms linking this neurotransmitter to reproduction are probably mediated by interplay between the serotonergic system, sex hormones, and other neurotransmitters.

How do we characterize temperament? Broad testing of temperament across time and contexts in low-variable conditions

In many species, individual animals often maintain relatively consistent individual differences in behaviour, indicative of temperament or personality. These stable individual differences are important for life history, survival and health consequences, and the field has seen exponential growth in temperament (e.g. boldness, exploration, sociability, aggression and activity) research. Quantification of animal temperament can be difficult because it requires (1) repeated behavioural measures from the same individual (to gauge within-individual consistency across time and contexts) and (2) identification of the most appropriate behaviour(s) to characterize temperament. In the current study, we took an atheoretical approach and conducted repeat, diverse behavioural tests in a low-variable environment to determine behaviours that were individually consistent over time and across conditions. To control environmental effects on behaviour, we conducted this work with individually housed outbred male Sprague–Dawley rats in a laboratory. To determine individual consistency, we measured each rat's behavioural response to five different arenas (i.e. different contexts) and repeated the five tests at three time points. To identify potential composite, multibehaviour estimates of temperament, we used factor analyses to determine behaviours that covaried on each test arena, and calculated factor scores. To determine individual consistency of behaviours and factor scores across time and contexts, we used reliability and correlation analyses. Several behaviours consistently covaried on each test, and with a few notable exceptions, the resulting factors tended to align with five commonly studied temperament categories. Certain behaviours/factors were more consistent across time and contexts than others; distance travelled/activity were highly consistent, as were sociality- and boldness-related behaviours, whereas aggression and exploration were less consistent. We did not find strong evidence that multibehaviour estimates of temperament (factor scores) were more consistent over time or across conditions than single-behaviour metrics. Where possible, similar atheoretical approaches to cross-time and cross-context behaviour testing will be beneficial for initial temperament characterization.

Weak evidence that asset protection underlies temporal or contextual consistency in boldness of a terrestrial crustacean

In recent years, many studies have investigated the potential state dependence of individual differences in behaviour, with the aim to understand the proximate and ultimate causes and consequences of animal personality. Among the potential state variables that could affect behavioural expression is size and mass, but few studies have found associations at the among-individual levels. Insufficient sampling and incorrect analysis of data are cited as impediments to detecting correlations, if they exist. Here, we conducted a study using 100 pillbugs (Armadillidium vulgare) and assayed their defensive behaviour 24 times each over time and across familiarity contexts, to test the asset protection hypothesis that predicts a negative correlation between boldness and mass, and with increases in mass over time. Multivariate mixed models revealed that despite mostly consistent individual behavioural differences over time (modest slope variance) and across contexts (near-parallel reaction norms), and 18-fold range in starting mass, there was no correlation between individual mean mass and boldness. However, individuals that gained more mass over time may have been more ‘shy’ compared to those gaining less mass, but the correlation was weak and observed variation in mass gain was small. There was also a mean level trend of increasing shyness over time that was coincident with mean level mass increases over time. Together, our study provides weak evidence for the asset protection hypothesis, whereby individuals that accumulate more resources are thought to protect them through risk averse behaviour.Significance statementIndividual variation in ‘state’, such as mass or energy reserves, is thought to be a predictor of individual differences in behaviour that are consistent over time. However, few studies reveal such links, and several studies suggest insufficient sampling may explain null results in most studies. We studied 100 animals sampled 24 times each in a controlled setting to reveal stable individual differences in mean behaviour over time and across contexts; however, individual behaviour was unrelated to large differences in individual mass but weakly related to increases in mass through time whereby individuals became more shy and those growing faster were somewhat more shy. Our results provide little evidence for the asset protection hypothesis.

Links between personality traits and problem-solving performance in zebra finches (Taeniopygia guttata).

Consistent individual differences in behaviour across time or contexts (i.e. personality types) have been found in many species and have implications for fitness. Likewise, individual variation in cognitive abilities has been shown to impact fitness. Cognition and personality are complex, multidimensional traits. However, previous work has generally examined the connection between a single personality trait and a single cognitive ability, yielding equivocal results. Links between personality and cognitive ability suggest that behavioural traits coevolved and highlight their nuanced connections. Here we examined individuals' performance on multiple personality tests and repeated problem-solving tests (each measuring innovative performance). We assessed behavioural traits (dominance, boldness, activity, risk-taking, aggressiveness and obstinacy) in 41 captive zebra finches. Birds' scores for boldness and obstinacy were consistent over two years. We also examined whether personality correlated with problem-solving performance on repeated tests. Our results indicate that neophobia, dominance and obstinacy were related to successful solving, and less dominant, more obstinate birds solved the tasks quicker on average. Our results indicate the importance of examining multiple measures over a long period. Future work that identifies links between personality and innovation in non-model organisms may elucidate the coevolution of these two forms of individual differences.

Animal personality: Worn whiskers reveal resilience

Consistent individual differences in behavior, or personality, may buffer populations against environmental changes. A long-term study of Galápagos sea lions reveals foraging polymorphisms with different levels of reproductive resilience as ocean temperatures increase.

Elusive workers are more likely to differentiate into replacement reproductives than aggressive workers in a lower termite.

One of the most intriguing questions in eusocial insects is to understand how the overt reproductive conflict in the colony appears limited when queens or kings are senescent or lost because the morphologically similar individuals in the colony are reproductively totipotent. Whether there are some individuals who preferentially differentiate into replacement reproductives or not has received little attention. The consistent individual behavioral differences (also termed "animal personality") of individuals from the colony can shape cunningly their task and consequently affect the colony fitness but have been rarely investigated in eusocial insects. Here, we used the termite Reticulitermes labralis to investigate if variations in individual personalities (elusiveness and aggressiveness) may predict which individuals will perform reproductive differentiation within colonies. We observed that when we separately reared elusive and aggressive workers, elusive workers differentiate into reproductives significantly earlier than aggressive workers. When we reared them together in the proportions 12:3, 10:5, and 8:7 (aggressive workers: elusive workers), the first reproductives mostly differentiated from the elusive workers, and the reproductives differentiated from the elusive workers significantly earlier than from aggressive workers. Furthermore, we found that the number of workers participating in reproductive differentiation was significantly lower in the groups of both types of workers than in groups containing only elusive workers. Our results demonstrate that the elusiveness trait was a strong predictor of workers' differentiation into replacement reproductives in R. labralis. Moreover, our results suggest that individual personalities within the insect society could play a key role in resolving the overt reproductive conflict.

Emergence of personality in weaning-age kittens of the domestic cat?

Individual differences in behavior (animal personality) have recently received much attention although less so in young mammals. We tested 74 preweaning-age kittens from 16 litters of domestic cats in five everyday contexts repeated three times each across a 3-week period: a handling test where an experimenter held the kitten, a test where a piece of raw beef was given to the kitten and gradually withdrawn, a test where the kitten was presented with a live mouse in a jar, a test where the kitten was briefly confined in a pet carrier, and an encounter with an unfamiliar human who first remained passive and then attempted to stroke the kitten. We found consistent individual differences in behavior in all tests except with the mouse, although less marked than in equivalent tests with adult cats. Differences in behavior were unrelated to sex, body mass, litter size, or maternal identity. We found only weak correlations in results among the tests (behavioral syndromes), again unlike findings in adult cats. We conclude that weanling kittens show consistent individual differences in behavior but in a different manner to adults. If and how the pattern of such differences changes across development remains to be studied.

Chimpanzee Extraversion scores vary with epigenetic modification of dopamine receptor gene D2 (DRD2) and early rearing conditions

ABSTRACT Chimpanzees have consistent individual differences in behaviour, also referred to as personality. Similar to human personality structure, five dimensions are commonly found in chimpanzee studies that show evidence for convergent and predictive validity (Dominance, Openness, Extraversion, Agreeableness, and Reactivity/Undependability). These dimensions are to some extent heritable, indicating a genetic component that explains part of the variation in personality scores, but are also influenced by environmental factors, such as the early social rearing background of the individuals. In this study, we investigated the role of epigenetic modification of the dopamine receptor D2 gene (DRD2) as a potential mechanism underlying personality variation in 51 captive chimpanzees. We used previously collected personality trait rating data and determined levels of DRD2 CpG methylation in peripheral blood samples for these same individuals. Results showed that DRD2 methylation is most strongly associated with Extraversion, and that varying methylation levels at specific DRD2 sites are associated with changes in Extraversion in nursery-reared, but not mother-reared, individuals. These results highlight the role of dopaminergic signalling in chimpanzee personality, and indicate that environmental factors, such as social experiences early in life, can have long-lasting behavioural effects, potentially through modification of the epigenome. These findings add to the growing evidence demonstrating the importance of the experience-dependent methylome for the development of complex social traits like personality.

Seasonality in the Emission of Contact Calls in Spix's Disc-Winged Bats (Thyroptera tricolor) Suggests a Potential Role in Mate Attraction

Multiple studies show that animals exhibit consistent individual differences in behavior, but they also experience short-term changes in their behavioral responses associated with seasonal events, most notably reproduction. We compare calling rates between the breeding and non-breeding seasons, and between males and females, in Spix's disk-winged bats (Thyroptera tricolor). This species performs an exchange of inquiry and response calls in a context of social coordination and these vocalizations are used by individuals to signal roost location. Our results indicate that during the breeding season all males vocalize and also emit a greater number of response calls. In females, we found that there is no significant difference in their vocal behavior during the breeding and non-breeding seasons. Even though being vocal leads to greater energy costs and risk of predation, males were more vocal and emitted more vocalizations when females are known to be ovulating. Therefore, our results suggest that response calls may not only facilitate group cohesion, as found in previous studies, but that it may also play a role in courtship.

Variation in boldness behaviour across individuals, sexes and strains of the guppy (

The concept of animal personality is based on consistent individual differences in behaviour, yet little is known about the factors responsible for such variation. Theory based on sex-specific selection predicts sexual dimorphism in personality-related traits and, in some cases, differences in trait variances between the sexes. In this study, we examined the sources of individual variation for boldness behaviour in guppies (Poecilia reticulata). We first demonstrated heightened boldness expression in males relative to females across feral wild types, artificially selected domestic ‘designer’ guppies, and putative hybrids of the two. Boldness and body size covaried at the strain level but were not associated among individuals within strains. We also found high and repeatable behavioural differences among individuals (0.40 > intraclass r > 0.60) in all sex/strain groups except hybrid strain females. However, there was no evidence for the heightened inter-individual male variance anticipated for personality traits subject to certain forms of directional sex-specific selection. Domestic fish were boldest overall, and indicated the largest sex difference, which is consistent with genetic linkage between boldness and male ornamental colouration. Consistently high intrinsic variation in boldness behaviour, which extends to inbred domesticated fish, may in part underpin the invasive potential of this species.

Exploration speed in captivity predicts foraging tactics and diet in free-living red knots.

Variation in foraging tactics and diet is usually attributed to differences in morphology, experience and prey availability. Recently, consistent individual differences in behaviour (personality) have been shown to be associated with foraging strategies. Bolder or more exploratory individuals are predicted to have a faster pace‐of‐life and offset the costs of moving more or in risky areas, with higher energetic gains by encountering profitable foraging opportunities and prey. However, the relationship between personality, foraging and diet is poorly understood.We investigated how exploratory behaviour in red knots Calidris canutus is associated with foraging tactics and diet by combining laboratory experiments, field observations and stable isotope analysis. First, we developed a mobile experimental arena to measure exploration speed in controlled settings. We validated the method by repeated testing of individuals over time and contexts. This setup allowed us to measure exploratory personality at the field site, eliminating the need to bring birds into captivity for long periods of time. After releasing birds within days of their capture, we asked whether exploration speed was associated with differences in foraging tactics and diet in the wild.We found that tactile foraging red knots mainly caught hard‐shelled prey that are buried in the sediment, whereas visual foraging knots only captured soft preys located close to or on the surface. We also found that faster explorers showed a higher percentage of visual foraging than slower explorers. By contrast, morphology (bill length and gizzard size) had no significant effect on foraging tactics. Diet analysis based on δ15N and δ13C stable isotope values of plasma and red blood cells confirmed our field observations with slower explorers mainly consumed hard‐shelled prey while faster explorers consumed more soft than hard‐shelled prey.Our results show that foraging tactics and diet are associated with a personality trait, independent of morphological differences. We discuss how consistent behaviour might develop early in life through positive feedbacks between foraging tactics, prey type and foraging efficiency.