Showing papers in "Behaviour in 2016"

A Brain Motivated to Play: Insights into the Neurobiology of Playfulness.

Abstract: Play is an important part of normal childhood development and is seen in varied forms among many mammals. While not indispensable to normal development, playful social experiences as juveniles may provide an opportunity to develop flexible behavioral strategies when novel and uncertain situations arise as an adult. To understand the neurobiological mechanisms responsible for play and how the functions of play may relate to these neural substrates, the rat has become the model of choice. Play in the rat is easily quantified, tightly regulated, and can be modulated by genetic factors and postnatal experiences. Brain areas most likely to be involved in the modulation of play include regions within the prefrontal cortex, dorsal and ventral striatum, some regions of the amygdala, and habenula. This paper discusses what we currently know about the neurobiological substrates of play and how this can help illuminate functional questions about the putative benefits of play.

The manifold use of pounding stone tools by wild capuchin monkeys of Serra da Capivara National Park, Brazil

Abstract: The use of pounding stone tools (PSTs) is a customary behaviour in several wild populations of capuchin monkeys; most of these monkeys use PSTs primarily to open hard palm nuts. Here, we describe the use of PSTs in two not previously studied groups of capuchin monkeys ( Sapajus libidinosus ) in Serra da Capivara National Park (SCNP), northeastern Brazil, and compare them to other groups and populations. Capuchins from SCNP are one of the only known population that habitually use PSTs for several purposes other than nut processing, including cracking seeds and fruits, breaking and/or enlarging holes in tree trunks or rocks, and pulverizing pebbles. Moreover, they use PSTs sequentially with probe stick tools to access hidden prey. The average size of PSTs was larger than the average locally available stones, suggesting active choice. The two groups exhibited more diversity in the use of PSTs than any other known population to date.

The role of male coloration in the outcome of staged contests in the European common wall lizard (Podarcis muralis)

Abstract: Colour signals play a key role in regulating the intensity and outcome of animal contests. Males of the common wall lizard (Podarcis muralis) show conspicuous ventrolateral ultraviolet (UV)-blue and black patches. In addition, some populations express a striking ventral colour polymorphism (i.e., discrete orange, white and yellow morphs). In this study, we set out to evaluate the potential signalling function of these colour patches by staging pairwise combats between 60 size-matched adult lizards (20 per morph). Combats were held in a neutral arena, with each lizard facing rivals from the three morphs in a tournament with a balanced design. We then calculated a fighting ability ranking using the Bradley–Terry model, and used it to explore whether ventral colour morph, the size of UV-blue and black patches or the spectral characteristics of UV-blue patches (i.e., brightness, hue, chroma) are good predictors of fighting ability. We did not find an effect of the UV-blue patches on contest outcome, but the size of black patches emerged as a good predictor of fighting ability. We also found that winners were more aggressive when facing rivals with black patches of similar size, suggesting that black patches play a role in rival assessment and fighting rules. Finally, we found that orange males lost fights against heteromorphic males more often than yellow or white males. In light of these results, we discuss the potential signalling function of ventrolateral and ventral colour patches in mediating agonistic encounters in this species.

Natural variation in brain gene expression profiles of aggressive and nonaggressive individual sticklebacks.

Abstract: Within many species, some individuals are consistently more aggressive than others. We examine whether there are differences in brain gene expression between aggressive versus nonaggressive behavioural types of individuals within a natural population of male three-spined sticklebacks ( Gasterosteus aculeatus ). We compared gene expression profiles of aggressive male sticklebacks to nonaggressive males in four regions of the brain (brainstem, cerebellum, diencephalon and telencephalon). Relatively few genes were differentially expressed between behavioural types in telencephalon, cerebellum and diencephalon, but hundreds of genes were differentially expressed in brainstem, a brain area involved in detecting threats. Six genes that were differentially expressed in response to a territorial intrusion in a previous study were also differentially expressed between behavioural types in this study, implying primarily non-shared but some shared molecular mechanisms. Our findings offer new insights into the molecular causes and correlates of behavioural plasticity and individual variation in behaviour.

Bigger babies are bolder: effects of body size on personality of hatchling snakes

Abstract: An animal’s susceptibility to risk may be partly dependent on its body size. But are larger individuals bolder? We assessed this question by measuring time to emerge from a shelter in repeated trials on hatchling keelback snakes (Tropidonophis mairii). Estimates of repeatability of emergence times suggested they measure some underlying personality dimension related to boldness. Larger hatchlings emerged from shelter sooner than small ones. Hatchling mass of keelbacks is substantially influenced both by maternal phenotype and by incubation conditions. Given the environmental basis of much of the variation in offspring size, the size-boldness association may reflect a facultative ability to adjust behavioural tactics to body size, as well as innate differences in personality traits between large versus small hatchlings. The link between size and boldness suggests that the survival advantage of larger offspring size in this population may be driven by snake behaviour as well as morphology.

Vervet monkey (Chlorocebus pygerythrus) alarm calls to leopards (Panthera pardus) function as a predator deterrent

Abstract: Behavioural predator–prey interactions are difficult to study, especially when predators avoid humans. To gain greater understanding of their dynamism, we conducted a 14-month field study in which we minimized human presence by employing acoustic recorders and camera traps, along with GPS collars deployed on vervet monkeys (Chlorocebus pygerythrus) and leopards (Panthera pardus) in Laikipia, Kenya. Recordings at the vervets’ sleeping site revealed that they gave ‘leopard’ alarm calls most frequently near dusk and dawn, whereas photographs showed that leopards approached vervets more closely at night, when the monkeys alarm-called less often. GPS data showed that after vervets alarm-called, leopards within 200 m quickly moved away, changing direction, but when vervets did not alarm-call, leopards continued moving forward. These results reveal that vervets’ leopard alarm calls function as a predator deterrent in addition to a conspecific warning call.

Metabolism, personality and pace of life in the Trinidadian guppy, Poecilia reticulata

Abstract: While among-individual variation in behaviour, or personality, is common across taxa, its mechanistic underpinnings are poorly understood. The Pace of Life syndrome (POLS) provides one possible explanation for maintenance of personality differences. POLS predicts that metabolic differences will covary with behavioural variation, with high metabolism associated with risk prone behaviour and ‘faster’ life histories (e.g., high growth, early maturation). We used a repeated measures approach, assaying metabolic traits (rate and scope), behaviour and growth to test these predictions in the Trinidadian guppy, Poecilia reticulata . We found that while individuals varied significantly in their behaviour and growth rate, more risk prone individuals did not grow significantly faster. Furthermore, after accounting for body size there was no support for among-individual variation in metabolic traits. Thus, while personality differences are clearly present in this population, they do not covary with metabolism and the POLS framework is not supported.

Play, variation in play and the development of socially competent rats

Abstract: Studies on laboratory rats ( Rattus norvegicus ) have revealed that experience with social play in the juvenile period is important for the development of improved social skills, an improvement that appears to be mediated by the prefrontal cortex. But there is much variation in both the frequency with which play occurs and in the complexity of the actions performed among different strains of rats. Is all this variation adaptive in serving play’s critical developmental role? The integrative approach advocated by Tinbergen provides a framework with which to assess such variation. A review of what is known and the inclusion of some novel data suggest that irrespective of the form of the play, rats of all strains converge on the same key experiences, experiences that have been implicated in the development of social skills. The lessons learnt from rats may serve as a guide for broader cross-species comparisons.

Fair play and its connection with social tolerance, reciprocity and the ethology of peace

Abstract: The concept of peace, with its corollary of behaviours, strategies and social implications, is commonly believed as a uniquely human feature. Through a comparative approach, we show how social play in animals may have paved the way for the emergence of peace. By playing fairly, human and nonhuman animals learn to manage their social dynamics in a more relaxed and tolerant way that results in a more effective management of conflicts. We show that play promotes tolerance, cooperation, fairness and reciprocity, which are essential elements of the so-called positive peace. This kind of peace is reached through an evolving process in which individuals continually modify social relationships to attain peaceful coexistence. In conclusion, we assume that the concept of peace has deep biological roots that constitute the basis for more sophisticated cultural constructions.

Obstacles and catalysts of cooperation in humans, bonobos, and chimpanzees: behavioural reaction norms can help explain variation in sex roles, inequality, war and peace

Abstract: Our closest living relatives, bonobos and chimpanzees, along with small-scale human societies figure prominently in debates about human nature. Here we emphasize and explain behavioural variation within and among these three species. In the logic of behavioural ecology, individuals have been selected to adjust their behaviour along evolved reaction norms that maximize fitness given current socio-ecological conditions. We discuss variation in three behavioural contexts: relationships between the sexes, hierarchy and inequality, and intergroup interactions. In each context, behavioural variation can be related to two broad socio-ecological conditions: (i) the defensibility of contested resources, and (ii) differences in bargaining power. When defensibility of resources and differences in bargaining power are great, interactions are rife with conflict; when they are minimal, interactions are more harmonious. These socio-ecological conditions therefore constitute key catalysts and obstacles of cooperation. We conclude that human nature should be seen as consisting of evolved reaction norms.

Stone handling, an object play behaviour in macaques: welfare and neurological health implications of a bio-culturally driven tradition

Abstract: Object play in primates is viewed as generally having no immediate functional purpose, limited for the most part to immature individuals. At the proximate level, the occurrence of object play in immatures is regarded as being intrinsically self-rewarding, with the ultimate function of supporting motoneuronal development and the acquisition of skills necessary to prepare them for survival as adults. Stone handling (SH), a solitary object play behaviour occurs, and has been studied, in multiple free-ranging and captive troops of provisioned Japanese macaques, as well as rhesus and long-tailed macaques for over 35 years now. A review of our combined findings from these observations reveal that infants acquire SH in the first 3-4 months of life and exhibit increasingly more complex and varied behavioural patterns with age. The longitudinal data shows that many individuals maintain this activity throughout life, practicing it under relaxed ecological and social conditions. The ultimate function may be bimodal, promoting motor development in young and neural maintenance and regeneration in adult and aging individuals.

On potential links between inequity aversion and the structure of interactions for the evolution of cooperation

Abstract: Despite the fact that most models of cooperation assume equal outcomes between individuals, in real life it is likely rare that this is the case. Does it make a difference for our understanding of the evolution of cooperation? Following a taxonomy of cooperation concepts that focuses on costs and benefits, we explore this question by considering the degree to which inequity aversion may provide one mechanism to stabilize cooperation. We suggest a key role for inequity aversion in some contexts in both biological markets and direct reciprocity, and highlight the potentially unique role of positive inequity aversion for human reputation games. Nevertheless, a key challenge is to determine how different animal species perceive the payoff structure of their interactions, how they see their interaction with their partners, and the degree to which simpler mechanisms, like contrast effects or the associative learning seen in optimal foraging, may produce similar outcomes.

Experimentally altered plumage brightness of female tree swallows: a test of the differential allocation hypothesis

Abstract: The differential allocation hypothesis posits that individuals should invest in the current reproductive attempt according to the attractiveness of their mate, but studies of allocation by males when female traits are manipulated to be more attractive are lacking. In the current study, we experimentally enhanced and reduced the plumage brightness of female tree swallows (Tachycineta bicolor) relative to controls to examine whether males adjust investment in parental care according to female attractiveness, while simultaneously performing a brood size manipulation. Contrary to our predictions, we found no evidence that males provisioned nestlings according to the plumage brightness of females. However, we found that nestling quality and fledging success were lowest when female plumage brightness was reduced and brood size was enlarged. This may be due to the plumage brightness treatment influencing agonistic interactions with other females, and may suggest that plumage brightness is a signal assessed by females.

Breaking the succession rule: the costs and benefits of an alpha-status take-over by an immigrant rhesus macaque on Cayo Santiago

Abstract: Explaining intraspecific variation in reproductive tactics hinges on measuring associated costs and benefits. Yet, this is difficult if alternative (purportedly less optimal) tactics remain unobserved. We describe a rare alpha-position take-over by an immigrant male rhesus macaque in a population where males typically gain rank via succession. Unusually, male aggressiveness after the take-over correlated with rank and mating success. The new alpha achieved the highest mating and reproductive success. Nevertheless, he sired only 4 infants due to high extra-group paternity (59.3%). The costs of his immigration tactic were high: after the mating season ended, unable to deter coalitionary attacks by resident males, he was overthrown. The following year he had the highest relative annual weight loss and levels of immune activation among males in the group. Succession-based rank-acquisition in large, provisioned groups of macaques thus appears to be actively maintained by resident males, who impose high costs on challengers.

Bonding beyond the pair in a monogamous bird: impact on social structure in adult rooks (Corvus frugilegus)

Abstract: The formation of social bonds outside the mated pair is not frequently reported in monogamous birds, although it may be expected in some species like rooks, living in groups all year round. Here we explore the social structure of captive adult rooks over three breeding seasons. We recorded proximities and affiliations (i.e., allofeeding, allopreening, contact-sit) to classify relationships according to their strength. Three categories of relationships emerged: primary (i.e., pairs), secondary and weak relationships. Affiliations and sexual behaviours were not restricted to pairs, and secondary relationships were clearly recognizable. Mixed-sex secondary relationships were qualitatively equivalent to pairs (i.e., same behaviours in the same proportions), although they were quantitatively less intense. Same sex pairs occurred, and were qualitatively equivalent to mixed-sex pairs. Overall we found that rooks social structure is more than just an aggregation of pairs, which highlights the importance of considering extra-pair relationships in socially monogamous birds.

Motivation, development and object play: comparative perspectives with lessons from dogs

Abstract: Object play occurs in diverse animals in addition to birds and mammals. Although many carnivores engage in object play in a predatory context, many non-predators do so also. Conjectures over the years on the motivation to play are reviewed dealing with intrinsic, developmental, and stimulus factors. We then report on quantitative studies of the play of puppies from 6 litters (3 breeds) when given 5 different toys with different sensory and functional properties at half week intervals from 3 to 7 weeks of age. The propensity to engage with objects begins early, play complexity increases rapidly, the structure of the play is similar to adult object play, and breed differences were found. Object play with predatory characteristics appears before weaning, suggesting that hunger is not the primary motivation. Studying the development of object play in different dog breeds may be useful in addressing questions of domestication and play evolution.

Variation among free-living spotted hyenas in three personality traits

Abstract: Inter-individual differences in behaviour, termed ‘animal personality’, are often consistent over time and across contexts and can be significantly related to fitness. However, most studies of animal personality are conducted in the laboratory or involve experimental protocols. Here, we used longitudinal scan and all-occurrence data collected under naturalistic conditions over 21 years to study boldness, aggressiveness, and sociability in a wild population of spotted hyenas (Crocuta crocuta). We found significant variation among individual hyenas in all three traits; however, whereas both sexes exhibited consistent inter-individual differences in aggressiveness and sociability, males were less consistent than females in their boldness. Heritability and maternal effects were small but significant for both boldness and sociability. A large proportion of the variation in aggressiveness could be attributed to genetic and maternal effects, supporting previous research linking hormone exposure in utero to aggressive behaviour later in life. All three traits were correlated with at least one measure of fitness. Particularly aggressive females were more successful in raising their offspring to reproductive maturity than less aggressive females. Interestingly, the reproductive benefits of sociability depended on social rank; for low-ranking hyenas, gaining feeding tolerance via sociability may significantly enhance reproductive success. Both boldness and sociability were linked to survival, but these traits affected longevity in different ways; highly social hyenas lived longer than those that were less social, but selection on boldness was stabilizing, favoring hyenas with intermediate boldness values that balance the benefits of risky behaviour against risks of injury and death.

Cumulative effects of body size and social experience on aggressive behaviour in a subsocial bee

Abstract: Dominance hierarchies represent some of nature’s most rudimentary social structures, and aggression is key to their establishment in many animal species. Previous studies have focused on the relative influences of prior experience and physiological traits of individuals in determining social rank through aggression. Here we examine the behavioural potential for dominance hierarchy formation in the subsocial small carpenter bee, Ceratina calcarata . Both physiological traits and social experience were found to play partial roles in predicting future interactive behaviour in this species. Our results suggest that individual size is associated with dominance in initial encounters, while prior experience plays a larger role in predicting dominance in subsequent encounters. Social systems in the early stages of social evolution may well have followed these same predictive factors and these factors are key targets for future studies of social evolution and the behavioural origins of dominance hierarchies.

A dear enemy relationship in a territorial cichlid: evidence for the threat-level hypothesis

Abstract: Despite competing for resources such as space, food and mates, many territorial animals are less aggressive towards neighbours who rarely go beyond their territorial boundaries. This so-called dear enemy phenomenon is advantageous in territorial defence, but it has not been well studied in fish. In this work, we tested the ‘correct–incorrect boundary paradigm’ of the dear enemy phenomenon using the territorial cichlid fish Neolamprologus pulcher, which exhibits dear enemy relationships. When the fish was placed in a small experimental tank, in which fish established its territory, it was initially very aggressive against a neighbouring fish in an adjacent tank, but the aggression level decreased rapidly (within 4 days). When the tank containing the neighbour was shifted to the opposite side, the focal fish was more aggressive than the day before, but it exhibited less aggression than it did against a stranger placed on the shifted side. This lower level of aggression suggested that the focal fish did not regard the shifted neighbour as a stranger. Our observations provide support for the threat-level hypothesis, according to which territory owners will modulate aggression intensity based on the threat level.

Evidence of ‘sickness behaviour’ in bats with white-nose syndrome

Abstract: Many animals change behaviour in response to pathogenic infections. White-nose syndrome (WNS) is a fungal skin disease causing rapid declines of North American bats. Infection with Pseudogymnoascus destructans causes hibernating bats to arouse from torpor too often, potentially causing starvation. Mechanisms underlying increased arousals are not understood but fungal invasion of the wings could trigger thirst to relieve fluid loss or grooming to relieve skin irritation. Alternatively, bats might exhibit ‘sickness behaviour’, a suite of responses to infection that save energy. We quantified behaviours of healthy and experimentally inoculated little brown bats ( Myotis lucifugus ) that could reflect active (i.e., drinking, grooming) or inactive (i.e., sickness behaviour) responses to infection. Infected bats groomed less and were less likely to visit their water dish compared to controls. These results are consistent with research suggesting that P. destructans causes sickness behaviour which could help bats compensate for energetic costs associated with infection.

Play fighting in Visayan warty pigs (Sus cebifrons): insights on restraint and reciprocity in the maintenance of play

Abstract: Restraint is thought to be essential to enable the reciprocity needed for play fighting to remain playful. Descriptions of playing in pigs suggest that they do not exhibit restraint. Analysis of videotaped sequences of play fighting in captive family groups of warty pigs was used to test three hypotheses about restraint and reciprocity. Hypothesis 1 asserts that the lack of restraint arises from neither participant handicapping its actions in favour of its opponent: this was supported. Hypothesis 2 asserts that the winner of a contest will show restraint by not prosecuting further attack: this was not supported. However, the winner did refrain from attacking if the loser signalled submission. Hypothesis 3 asserts that restraint by the winner will allow reciprocal attacks by the loser — this was supported. The dissociation of restraint and reciprocity evident in the pigs offers some new insights into the evolution of play fighting.

Affiliation, dominance and friendship among companion dogs

Abstract: Dog social behaviour has been well studied, but little is known about affiliative relationships between dogs. We report a yearlong study of dominance and affiliation in 24 dogs at a dog daycare facility and provide additional details on dog relationships through long-term observations of pairs of dogs who lived together in the same household or met frequently for years. Companion dogs formed highly differentiated relationships with one another. At daycare, some dyads affiliated and displayed one-way submission (formal dominance), others affiliated without a dominance relationship (egalitarian), and the majority of dyads did not affiliate at all (agonistic or non-interactive). The dogs in household environments showed formal and egalitarian relationships, and two dyads exchanged two-way agonism without submission (unresolved). Sex influenced the types of relationships dogs formed, with mixed sex dyads more likely to affiliate and less likely to exhibit dominance than same-sex pairs. Dominance influenced the nature of affiliation in relationships; egalitarian dyads were more likely to play and showed more equitable gentle affiliation. Gentle affiliation was reciprocal in the group as a whole, but it was highly skewed in many dyads, especially those with dominance relationships. Gentle affiliation was usually, but not always, directed up the hierarchy. Certain dyads affiliated at much higher rates than others, indicating that the dogs formed friendships. Most friends were mixed sex and/or egalitarian pairs, but friendships occurred in all of the sex class/dominance combinations. Long-term observations demonstrated how dyadic relationships can change over time. Such highly differentiated relationships suggest significant social complexity in dogs.

Sexual segregation in human conversations

Abstract: Human conversation groups have a characteristic size limit at around four individuals. Although mixed-sex social groups can be significantly larger than this, census data on casual social groups suggest that there is a fractal pattern of fission in conversations when social group size is a multiple of this value. This study suggests that, as social group size increases beyond four, there is a tendency for sexual segregation to occur resulting in an increasing frequency of single-sex conversational subgroups. It is not clear why conversations fragment in this way, but a likely explanation is that sex differences in conversational style result in women (in particular) preferring to join all-female conversations when a social group is large enough to allow this.

Effects of maternal stress and cortisol exposure at the egg stage on learning, boldness and neophobia in brook trout

Abstract: The environment experienced by females can have long-lasting effects on offspring phenotype. The objective of this study was to determine if maternal stress-induced behaviour reprogramming in offspring is found in brook char and to test whether cortisol is the main mediator, by separating the potential effects of cortisol from that of other potential maternal factors. We exposed female brook trout (Salvelinus fontinalis) to different parallel treatments during the oogenesis period: undisturbed as controls (1) fed cortisol through food (2) or physically stressed by handling once a week (3). Additionally, we exposed half of the control eggs to a cortisol suspension before fertilisation (4). Cortisol consumption and handling did not elevate either maternal plasma or egg cortisol, although egg cortisol level was significantly increased when eggs were bathed in the suspension. We measured spatial learning and memory, boldness and neophobia in 6 month-old offspring and found no effects of treatments on learning, memory or behaviour. Our results suggest that the relationship between maternal stress, circulating and egg cortisol levels, other maternal factors, and behavioural reprogramming is context and species-specific.

Are naive birds attracted to herbivore-induced plant defences?

Abstract: Arthropod herbivory induces the emission of plant volatiles that can be used by natural enemies of the herbivores to find their prey. Recently it has been shown that insectivorous birds also use these volatiles to locate their prey. Results of a previous study showed that birds with experience in foraging for caterpillars in trees were able to discriminate between caterpillar-infested and uninfested trees, even in the absence of caterpillars or their damage on leaves. Here, we tested whether the attraction to caterpillar-infested trees is exhibited in birds naive with respect to finding caterpillars on trees. Results show that naive great tits (Parus major) were not attracted to infested trees, when they could not see the larvae or their feeding damage. Naive birds cannot discriminate between caterpillar-infested and uninfested trees. Therefore, the attraction to caterpillar-infested trees does not seem to be innate in great tits, and may be acquired through learning.

Agonistic support towards victims buffers aggression in geladas (Theropithecus gelada)

Abstract: Agonistic support occurs when a bystander intervenes in an ongoing conflict. The consequences of agonistic support may differ when provided to victims or aggressors. Supporting victims may not only protect them, but also limit the escalation of aggression among group members. Our results on Theropithecus gelada showed that support was preferentially directed towards victims and high-ranking individuals provided the highest levels of support. Whereas the support towards the aggressor had no effect in reducing its renewed aggression, it increased the frequency of subsequent conflicts among fellows. The support towards victims significantly reduced subsequent aggression both towards the victim and among other group members. The support was biased towards victims who were unrelated and shared weak bonds with the aggressors. In conclusion, victim support may be a social tool, which intervenes when other mechanisms are less likely to occur such as the case when the opponents are not kin or friends.

Aggression and hierarchical steepness inhibit social play in adult wolves

Abstract: In canids, play dynamics seem to be more affected by dominance hierarchy rather than cooperative social bonds. To test this hypothesis we studied a colony of grey wolves (Canis lupus lupus). We quantified the dynamics of aggression and hierarchical changes in two periods (Sample 1 and Sample 2). Sample 2 was characterized by higher level of aggressiveness and by a more strict and steep linear hierarchy. The negative correlation between rank distance and play frequency characterizing both periods and the higher play asymmetry in Sample 2 suggest that rank rules dictate play rules thus highlighting the competitive side of wolf play behaviour. The overall affiliation rates showed no variation between the two samples. Yet, play performance was modified. In Sample 2, wolves reduced playful activity, limited the number of players per session and avoided playing during high competition contexts. Our findings support the hypothesis that wolf play is modulated by dominance relationships more than by cooperative social bonds.

The opposite effects of routine metabolic rate and metabolic rate during startle responses on variation in the predictability of behaviour in hermit crabs

Abstract: Studies on animal behaviour have suggested a link between personality and energy expenditure. However, most models assume constant variation within individuals, even though individuals vary between observations. Such variation is called intraindividual variation in behaviour (IIV). We investigate if IIV in the duration of the startle response is associated with metabolic rates (MR) in the hermit crab Pagurus bernhardus . We repeatedly measured startle response durations and MR during each observation. We used double hierarchical generalized linear models to ask whether among and IIV in behaviour was underpinned by MR. We found no association between the mean duration of the startle responses and either routine MR or MR during startle response. Nevertheless, we found that IIV increased with MR during startle responses and decreased with routine MR. These results indicate that crabs with higher MR during startle responses behave less predictably, and that predictability is reduced during exposure to elevated temperatures.

Into the wild: developing field tests to examine the link between elasmobranch personality and laterality

Abstract: The field of animal personality has received considerable attention in past decades, yet few studies have examined personality in the wild. This study investigated docility, a measure of boldness, in two Port Jackson shark ( Heterodontus portusjacksoni ) populations using field tests, and if laterality differences explained docility levels. We developed a struggle test as an assay for docility, which is particularly amenable to field studies. The struggle test was effective, and repeatable inter-individual docility differences were observed. Sex, but not population, influenced docility scores, with male sharks being less docile than females. This difference is likely due to the contrasting role each sex plays during mating. We also found individualized lateralization. However, no individual-level relationship between lateralization and docility was detected. Despite reported links between laterality and some personality traits, the relationship between laterality and boldness remains inconclusive in sharks. Further studies will prove essential to clarify the mechanisms behind personality traits in vertebrates.