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Abstract

The concept of personality implies individual differences in behavior and physiology that show some degree of repeatability/consistency over time and across contexts. Most studies of animal personality, particularly studies of individuals' variation in physiological mechanisms, have been conducted on selected individuals in controlled conditions. We attempted to detect consistent behaviors as well as physiological patterns in greylag ganders (Anser anser) from a free-roaming flock living in semi-natural conditions. We tested 10 individuals repeatedly, in a handling trial, resembling tests for characterization of “temperaments” in captive animals. We recorded the behavior of the same 10 individuals during four situations in the socially intact flock: (1) a “low density feeding condition”, (2) a “high density feeding condition”, (3) a “low density post-feeding situation” and (4) while the geese rested. We collected fecal samples for determination of excreted immuno-reactive corticosterone (BM) and testosterone metabolites (TM) after handling trials, as well as the “low density feeding” and the “high density feeding” conditions. BM levels were very highly consistent over the repeats of handling trials, and the “low density feeding condition” and tended to be consistent over the first two repeats of the “high density feeding condition”. Also, BM responses tended to be consistent across contexts. Despite seasonal variation, there tended to be inter-test consistency of TM, which pointed to some individual differences in TM as well. Aggressiveness turned out to be a highly repeatable trait, which was consistent across social situations, and tended to correlate with an individual's resistance during handling trials. Also, “proximity to the female partner” and “sociability” – the average number of neighboring geese in a close distance while resting – were consistent. We conclude that aggressiveness, “affiliative tendencies” and levels of excreted corticosterone and testosterone metabolites may be crucial factors of personality in geese.

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... We first assessed exploration tendencies of females in a standard test cage with which birds were unfamiliar [20][21][22]. Female choice was then tested in a four-chamber apparatus, a device regularly used to assess female sexual preference in zebra finches [10,23], and more generally, in vertebrates [24,25]. ...
... For each trial, three stimuli-males were randomly assigned to one of the four arms of the apparatus. In addition, one control-female was randomly assigned to one arm to control for focal female's sexual motivation [24,29]. The position of stimuli-individuals was also randomized among trials. ...
... In some cases, hormones such as corticosterone, testosterone, or neuropeptides such as arginine vasotocin mediate switches between different ART phenotypes [22,23]. Interestingly, testosterone and corticosterone titres are linked to personality in some birds [24][25][26]. This suggests that the same proximate determinants could be involved in the development of both ART and personality (figure 1) [27,28, see[29] for a between-species comparison]. ...
Article
In evolutionary biology, phenotypic variation has for a long time been considered as the raw material on which natural selection acts. However, research on the consistency of behaviour led to the development of the animal personality concept during the 1990s. This concept was based on the characterization of traits such as neophobia, aggressiveness, exploratory tendencies and risk-taking behaviour. Since then, several studies have shown that personality can evolve through natural selection and is related to many life-history traits, such as dispersal or anti-predator behaviour.Pairing strategies and foraging strategies are two fundamental components of an organism's life, but their relationships with personality have so far been neglected. In this thesis, we determined the extent to which personality influences sexual and feeding behaviour, using the zebra finch (Taeniopygia guttata) as a model organism. Our work highlights the role of natural and sexual selection on the maintenance of personality variation.Some personality traits are related to each other within our sample, defining a behavioural syndrome. Moreover, personality predicted feeding success in competitive situations, but differently for scramble and interference competition. Proactive individuals were dominant in interference competition but had lower feeding success in producer-scrounger games. Interestingly, these results suggest that natural selection could favour different personalities depending on the context, perhaps explaining the maintenance of personality variation within populations. Moreover, personality could constrain behavioural optimality across situations. Finally, in a mate-choice context, we found that female personality influences selectivity, preference and its repeatability during spatial association tests.The joint study of personality and pairing and foraging strategies thus represents a promising avenue of research for understanding the maintenance of personality variation through natural and sexual selection. Moreover, personality can considerably influence some life-history traits in sexual and foraging contexts
... We found no evidence of among-individual variance in FAM concentrations in this study. This contrasts with the limited results published for other taxonomic groups, which show significant repeatability of both plasma testosterone (lizards: While et al., 2010) and faecal androgen metabolites (Kralj-Fisher et al., 2007;Pelletier et al., 2003) in wild systems. It is worth noting, however, that these studies were either considered repeatability within the shorter time-periods of days (Pelletier et al., 2003) or months (Kralj-Fisher et al., 2007;While et al., 2010) or were based on much smaller sample sizes (Kralj-Fisher et al., 2007;While et al., 2010), than our study which collected samples over several years. ...
... This contrasts with the limited results published for other taxonomic groups, which show significant repeatability of both plasma testosterone (lizards: While et al., 2010) and faecal androgen metabolites (Kralj-Fisher et al., 2007;Pelletier et al., 2003) in wild systems. It is worth noting, however, that these studies were either considered repeatability within the shorter time-periods of days (Pelletier et al., 2003) or months (Kralj-Fisher et al., 2007;While et al., 2010) or were based on much smaller sample sizes (Kralj-Fisher et al., 2007;While et al., 2010), than our study which collected samples over several years. The lack of any among-individual variance in FAM concentrations meant we did not examine covariances with cumulative harem size at the level of the individual. ...
... This contrasts with the limited results published for other taxonomic groups, which show significant repeatability of both plasma testosterone (lizards: While et al., 2010) and faecal androgen metabolites (Kralj-Fisher et al., 2007;Pelletier et al., 2003) in wild systems. It is worth noting, however, that these studies were either considered repeatability within the shorter time-periods of days (Pelletier et al., 2003) or months (Kralj-Fisher et al., 2007;While et al., 2010) or were based on much smaller sample sizes (Kralj-Fisher et al., 2007;While et al., 2010), than our study which collected samples over several years. The lack of any among-individual variance in FAM concentrations meant we did not examine covariances with cumulative harem size at the level of the individual. ...
Article
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Although it is known that hormone concentrations vary considerably between individuals within a population, how they change across time and how they relate to an individual's reproductive effort remains poorly quantified in wild animals. Using faecal samples collected from wild red deer stags, we examined sources of variation in faecal cortisol and androgen metabolites, and the potential relationship that these might have with an index of reproductive effort. We also biologically validated an assay for measuring androgen metabolites in red deer faeces. We show that variation in hormone concentrations between samples can be accounted for by the age of the individual and the season when the sample was collected. Faecal cortisol (but not androgen) metabolites also showed significant among-individual variation across the 10-year sampling time period, which accounted for 20% of the trait's phenotypic variance after correcting for the age and season effects. Finally, we show that an index of male reproductive effort (cumulative harem size) during the mating season (rut) was positively correlated with male cortisol concentrations, both among and within individuals. We suggest that the highest ranking males have the largest cumulative harem sizes (i.e. invest the greatest reproductive effort), and that this social dominance may have associated behaviours such as increased frequency of agonistic interactions which are associated with corresponding high levels of faecal cortisol metabolites (FCM). Copyright © 2015. Published by Elsevier Inc.
... This finding adds to a growing body of evidence demonstrating that food deprivation can alter the repeatability of personality traits in spiders (Pruitt et al. 2011b;DiRienzo and Montiglio 2016), which are perennial models in animal personality research (Hedrick and Riechert 1989;Johnson and Sih 2005;Kralj-Fišer and Schneider 2012;Royauté et al. 2014). Despite the abundance of research addressing the ecological relevance of animal personality (Sih et al. 2012;Wolf and Weissing 2012), little research has probed the causes and consequences of variation in repeatability (Kralj-Fišer et al. 2007;Briffa and Greenaway 2011;Schuett et al. 2011). This study highlights how state variables can shape this central aspect of personality. ...
... Specifically, we found that prolonged food restriction was associated with reduced among-individual variation in both boldness and aggressiveness for the majority of the species investigated here. These data add to the growing interest into the causes and consequences of variation in behavioral repeatability (Kralj-Fišer et al. 2007;Schuett et al. 2011;Briffa et al. 2013) and together suggest that population-level variation among individuals is enhanced when individuals are in better condition, or, put another way, food deprivation can eliminate personality. Results like these may, in turn, help to explain why behavioral repeatability often tends to be site-specific (van Dongen et al. 2010) and situationally specific (Bell and Sih 2007) and may allow us to predict when and where personality will emerge. ...
Article
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Variation in state, which is any factor that alters the value of decision options, is likely one of the most common drivers of personality differences. However, the general relationship between individuals’ body state and various personality metrics/average behavioral type, repeatability of behavior, and behavioral syndrome structure is still poorly resolved. Here, we manipulate body condition in three spider species (Agelenopsis aperta, Latrodectus hesperus, and Anelosimus studiosus) using contrasting feeding schedules. We then assessed the effects of historic feeding regime on individuals’ body condition, boldness, and foraging aggressiveness. We further assessed the effects of feeding regimes on the repeatability of boldness and aggressiveness and the presence/absence of correlations between these two traits. We found that feeding treatment impacted individuals’ average boldness and aggressiveness in two species (A. aperta and A. studiosus). We also noted that among-individual variance in both boldness and aggressiveness was severely reduced when A. aperta and A. studiosus were subjected to prolonged food restriction, steeply reducing repeatability in these traits. Finally, we noted that correlations between boldness and foraging aggressiveness were detectable only in one case, revealing no compelling relationship between food restriction and the presence/absence of behavioral correlations. Taken together, our results suggest that food restriction has only weak, circumstantial effects on individuals’ average personality type and the correlations between behavioral traits. However, there appears to be a robust positive relationship between food availability and the signature of consistent individual differences in behavior. Significance statement Under laboratory conditions, we found that lower feeding rates sharply decreased the repeatability of aggressiveness and boldness in two spider species. In doing so, we provide the second body of evidence suggesting that a highly prevalent and ecologically relevant state variable, higher body condition, can increase the repeatability of foraging-related behavioral traits. Additionally, under some feeding regimes, we found that hunger levels could alter the average individual aggressiveness and boldness but not correlations between these traits. This work highlights the importance of state variables such as hunger in eroding behavioral repeatability, the defining trait of personality.
... way they are attracted and depend on the presence of other group members. Sociability has been studied mainly in domestic animals (cattle, Müller & Schrader 2005 ; Japanese quail Coturnix japonica , Faure & Mills 1998 ;sheep, Sibbald & Hooper 2004 ) and captive animals (spotted hyenas Crocuta crocuta , Gosling 1998 a ; greylag geese Anser anser , Kralj-Fišer et al . 2007 ). This can be explained by the fact that social isolation experiments are easier to perform with captive animals than in the wild. For example, Faure and Mills ( 1998 ) measured sociability by separating an individual quail from the group and measuring the distance the quail would cover on a treadmill to join the group. Nevertheless, i ...
... ation experiments are easier to perform with captive animals than in the wild. For example, Faure and Mills ( 1998 ) measured sociability by separating an individual quail from the group and measuring the distance the quail would cover on a treadmill to join the group. Nevertheless, it is possible to measure sociability in the fi eld. For example, Kralj-Fišer et al . ( 2007 ) measured the average number of neighbouring geese resting in close proximity to a focal individual. Alternatively, it might be possible to use indices from social network theory ( Chapter 9 ; Krause et al . 2007 ) as measures of social personality traits. ...
Article
Overview Animals differ in their behaviour, as humans differ in personality. Animal personality represents consistent behavioural individual differences over time and across contexts, and/or correlations between different types of behaviour. In many animal species, individuals differ in activity, aggressiveness, risk-taking and exploratory behaviour, and these behaviours are often positively correlated with each other. We therefore expect that personality affects social behaviour, and that social behaviour also influences personality. New discoveries about the evolutionary ecology of personality suggest exciting research opportunities on the effects of personality on the fate of individuals in social contexts, and on the influences of social interactions on development and evolution of personality. Studying personality in a social context can provide new insights in the study of social behaviour because it allows us to consider one important question: are social groups composed of individuals with varying degrees of specialisation? Here we consider that the degree of specialisation of an individual for a given trait corresponds to the range of phenotypic expression of that trait for that individual relative to its population. A specialist for a trait is limited in its range of expression of that trait relative to its population, whereas a generalist expresses the whole range of phenotypic variation observed for that trait in the population.
... Examples include studies of behavioral phenotypes, temperaments, or personalities in both vertebrate and non-vertebrate species (refer to [1] for a review). These studies have underlined several inter-individual differences in different traits, such as aggressiveness [2,3], activity levels [4,5], sociability [3], and boldness [6]. Individual competition may favor the expression of traits that improve reproductive fitness, although these specific adaptations are often costly in terms of energy and survival at both the morpho-physiological and behavioral levels [7][8][9]. ...
... Examples include studies of behavioral phenotypes, temperaments, or personalities in both vertebrate and non-vertebrate species (refer to [1] for a review). These studies have underlined several inter-individual differences in different traits, such as aggressiveness [2,3], activity levels [4,5], sociability [3], and boldness [6]. Individual competition may favor the expression of traits that improve reproductive fitness, although these specific adaptations are often costly in terms of energy and survival at both the morpho-physiological and behavioral levels [7][8][9]. ...
Article
In this paper, we review the scientific reports of sex-related differences in dogs as compared to the outcomes described for wild animals. Our aim was to explore whether the differences in male and female dogs were affected by the domestication process, in which artificial selection is the main driver. For this purpose, we used information regarding personality traits, cognitive processes, and perception, for which there is a wide theoretical framework in behavioral ecology. Aggressiveness and boldness, described as a behavioral syndrome, were reported as being higher in males than females. Females also seemed more inclined to interspecific social interactions with humans in tasks that require cooperative skills, whereas males appeared more inclined to social play, thus implying different levels of social engagement between the sexes, depending on the context. Studies on cognitive processes underlined a greater flexibility in resorting to a particular navigation strategy in males. Most lateralization studies seem to support the view that males are preferentially left-handed and females are preferentially right-handed. Reports on visual focusing coherently rank females as superior in focusing on single social and physical stimuli. Only male dogs are able to discriminate kin; however, the timing of the olfactory recording in sexes is related to the stimulus relevance. Dogs are largely in line with life-history theories, which indicate that sex differences in dogs are mainly rooted in their biological and evolutionary heritage, remaining unchanged despite artificial selection. In contrast, the higher intraspecific sociability in wild male animals was not replicated in dogs.
... This also suggests intra-individual plasticity in both coping styles and cognitive-behavioral syndromes. Earlier research demonstrated a strong genetic control of both copingstyles (Henry and Stephens, 1977;Koolhaas et al., 1999;Carere et al., 2003;Veenema et al., 2003;Kralj-Fišer et al., 2007) as well as personality or behavioral types (Dingemanse et al., 2002(Dingemanse et al., , 2003Drent et al., 2003;Dingemanse and Réale, 2005;Groothuis and Carere, 2005) in a number of different systems. Here we are finding patterns that suggest the possibility that individual males will transition their behavior, cognition, and coping style physiology to adopt an alternative reproductive role within a lifetime. ...
Article
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Sexual selection is a powerful diversifier of phenotype, behavior and cognition. Here we compare cognitive-behavioral traits across four reproductive phenotypes (females and three alternative males) of wild-caught ocellated wrasse (Symphodus ocellatus). Both sex and alternative male phenotypes are environmentally determined with sex determination occuring within the first year, and males transition between alternative phenotypes across 2 years (sneaker to satellite or satellite to nesting). We captured 151 ocellated wrasse and tested them on different behavior and cognition assays (scototaxis, shoaling, and two detour-reaching tasks). We found greater divergence across alternative male reproductive phenotypes than differences between the sexes in behavior, problem-solving, and relationships between these traits. Nesting males were significantly less bold than others, while sneaker males were faster problem-solvers and the only phenotype to display a cognitive-behavioral syndrome (significant correlation between boldness and problem-solving speed). Combining these results with prior measurements of sex steroid and stress hormone across males, suggests that nesting and sneaker males represent different coping styles. Our data suggests that transitioning between alternative male phenotypes requires more than changes in physiology (size and ornamentation) and mating tactic (sneaking vs. cooperation), but also involves significant shifts in cognitive-behavioral and coping style plasticity.
... Long term stress can also decrease the sensitivity of glucocorticoid receptors present in the brain (Banerjee et al., 2012;Hodgson et al., 2007) which potentially modifies the negative feedback loops of stress hormone expression (Romero, 2004;Zimmer et al., 2013). Therefore responses to stress and levels of circulating CORT are often considered stable traits (Evans et al., 2006;Jenkins et al., 2014;Kralj-Fišer et al., 2007; although see Ouyang et al., 2011), and have been suggested to drive individual differences in avian temperament or personality (Baugh et al., 2012;Cockrem, 2007;Moretz et al., 2007). Although many species show individual and population level variation in stress hormone expression (e.g. ...
Article
Full-text available
Many species show individual variation in neophobia and stress hormones, but the causes and consequences of this variation in the wild are unclear. Variation in neophobia levels could affect the number of offspring animals produce, and more subtly influence the rearing environment and offspring development. Nutritional deficits during development can elevate levels of stress hormones that trigger long-term effects on learning, memory, and survival. Therefore measuring offspring stress hormone levels, such as corticosterone (CORT), helps determine if parental neophobia influences the condition and developmental trajectory of young. As a highly neophobic species, jackdaws ($\textit{Corvus monedula}$) are excellent for exploring the potential effects of parental neophobia on developing offspring. We investigated if neophobic responses, alongside known drivers of fitness, influence nest success and offspring hormone responses in wild breeding jackdaws. Despite its consistency across the breeding season, and suggestions in the literature that it should have importance for reproductive fitness, parental neophobia did not predict nest success, provisioning rates or offspring hormone levels. Instead, sibling competition and poor parental care contributed to natural variation in stress responses. Parents with lower provisioning rates fledged fewer chicks, chicks from larger broods had elevated baseline CORT levels, and chicks with later hatching dates showed higher stress-induced CORT levels. Since CORT levels may influence the expression of adult neophobia, variation in juvenile stress responses could explain the development and maintenance of neophobic variation within the adult population.
... Therefore responses to stress and levels of CORT expression are often considered stable traits (Evans et al., 2006;Jenkins et al., 2014;Kralj-Fišer et al., 2007; although see Ouyang et al., 2011), and have been suggested to drive individual differences in avian temperament (Baugh et al., 2012;Cockrem, 2007;Moretz, Martins, & Robison, 2007). Although many species ...
Thesis
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Neophobia, or the fear of novelty, is thought to restrict animals’ ecological niches and hinder their propensity for innovation; two processes that should limit behavioural adjustment to human-induced changes in the environment. However, birds within the corvid family ($\textit{Corvidae}$) defy this trend by being highly neophobic, yet highly successful alongside humans across diverse habitats. This thesis examines the causes and ecological consequences of neophobia to unravel corvids’ puzzling neophobic tendencies. Throughout the thesis I find evidence that corvids are very neophobic, but that individuals differ in their level of novelty avoidance. Neophobia is not a fixed trait across time and towards all types of novelty. Neophobia levels differ depending on the type of novel stimuli being presented, and individuals can be inconsistent when environments change seasonally (Chapter Three). Although individual differences in neophobia are expected to be associated with fitness outcomes, I found no direct connections between neophobia, reproductive success or offspring stress hormone expression (Chapter Four). Moreover, if neophobia levels were defined by human presence, populations should differ in their novelty avoidance according to their proximity to humans. However, corvids show similar patterns of object neophobia between urban and rural areas (Chapter Five). The lack of connection between neophobia, fitness, and urbanization indicates that corvids might be able to circumvent individual differences in neophobia that might otherwise restrict behavioural adjustment. Accordingly, experience observing conspecifics consume novel foods and approach threatening objects encourages individual risk-taking, such that highly neophobic individuals could benefit from social information (Chapter Six). I therefore propose that corvids’ flexibility and their success alongside humans may be due to their ability to overcome their fear through learning. How animals make decisions in the face of ecological novelty may predict whether they behaviourally adjust to human-altered habitats and is relevant in the wider context of species conservation.
... Narayan et al. 2012Narayan et al. , 2013 and birds (r = 0.1-0.8- Cockrem and Silverin 2002;Kralj-Fišer et al. 2007;Rensel and Schoech 2011), but it is higher than the only other study in a wild, free-living mammal species (r = 0.15-Boonstra and Boag 1992). However, Boonstra and Boag (1992) analyzed repeatability within rather than among male meadow vole (Microtus pennsylvanicus) individuals, which may explain why their repeatability calculation is lower than ours. ...
Article
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While livetrapping is a vital field research tool, it is not a completely unbiased method of sampling. Biased trapping arises during field endocrinological studies whenever hormone levels or response influence the probability of capture of a subject. We repeatedly captured wild, free-living adult degus (Octodon degus) from the same location over 12 days to determine whether individuals with a certain endocrine stress profile were more likely to be captured repeatedly than others. We measured baseline cortisol (CORT), stress-induced CORT, and negative feedback efficacy via a dexamethasone suppression test in adult male and lactating and nonlactating female degus upon initial capture. We successfully recaptured approximately half of the degus. None of the 3 indices of the stress response at initial capture predicted whether a degu would be recaptured. However, baseline CORT levels at 1st capture had a weak, negative relationship with the number of days between 1st and 2nd capture. Because most animals interpret capture and restraint as an acute stressor, we also analyzed the effect of recapture on the endocrine stress response. Baseline and stress-induced CORT concentrations were measured upon each subsequent recapture for up to 5 total captures. Upon subsequent recaptures, neither stress-induced CORT nor baseline CORT changed significantly. Additionally, individual stress-induced and baseline CORT titers were repeatable within our sample population. These findings suggest that livetrapping does not select for animals with certain endocrine stress profiles, and that degus fail to habituate to repeated capture and restraint stress. Aunque la captura viva de animales ha sido fundamental en estudios de campo, el método de captura puede incluir algunos sesgos. En estudios conductuales y endocrinológicos estos sesgos se producen cuando la probabilidad de captura de un individuo es afectada por su respuesta o por niveles hormonales. Se capturaron y recapturaron individuos silvestres del roedor Octodon degus durante 12 días para determinar si los individuos con un perfil hormonal particular en respuesta a estrés por captura tienen una mayor probabilidad de ser capturados. Se examinaron tres componentes de la respuesta fisiológica de estrés en degus hembras y machos: nivel basal de cortisol, nivel de cortisol inducido por estrés, y eficacia del sistema de retroalimentación negativa (a través de un ensayo con dexametazona). Durante el estudio se recapturaron cerca de la mitad de los individuos marcados originalmente. Ninguno de los tres componentes de la respuesta de estrés examinado fue capaz de predecir la probabilidad de recaptura en los degus examinados. Tampoco se detectó una relación entre los niveles de cortisol medidos en la primera captura y el tiempo transcurrido hasta la primera recaptura. También se examinó un posible efecto del número de recapturas sobre los niveles de cortisol basal y cortisol inducido por estrés. Aunque los niveles de cortisol inducido por estrés no cambiaron con el número de capturas, si se registró una disminución en los niveles basales de cortisol. Por último, detectamos que los niveles de cortisol basal y cortisol inducido por estrés son repetibles en la población estudiada. En conjunto, los resultados indicaron que el trampeo reiterado no selecciona degus con perfiles hormonales particulares y que estos animales no muestran hábito al estrés producto de captura e inmovilización reiteradas.
... Long term stress can also decrease the sensitivity of glucocorticoid receptors present in the brain (Banerjee et al., 2012;Hodgson et al., 2007) which potentially modifies the negative feedback loops of stress hormone expression (Romero, 2004;Zimmer et al., 2013). Therefore responses to stress and levels of circulating CORT are often considered stable traits (Evans et al., 2006;Jenkins et al., 2014;Kralj-Fišer et al., 2007; although see Ouyang et al., 2011), and have been suggested to drive individual differences in avian temperament or personality (Baugh et al., 2012;Cockrem, 2007;Moretz et al., 2007). Although many species show individual and population level variation in stress hormone expression (e.g. ...
Article
Full-text available
Many species show individual variation in neophobia and stress hormones, but the causes and consequences of this variation in the wild are unclear. Variation in neophobia levels could affect the number of offspring animals produce, and more subtly influence the rearing environment and offspring development. Nutritional deficits during development can elevate levels of stress hormones that trigger long-term effects on learning, memory, and survival. Therefore measuring offspring stress hormone levels, such as corticosterone (CORT), helps determine if parental neophobia influences the condition and developmental trajectory of young. As a highly neophobic species, jackdaws (Corvus monedula) are excellent for exploring the potential effects of parental neophobia on developing offspring. We investigated if neophobic responses, alongside known drivers of fitness, influence nest success and offspring hormone responses in wild breeding jackdaws. Despite its consistency across the breeding season, and suggestions in the literature that it should have importance for reproductive fitness, parental neophobia did not predict nest success, provisioning rates or offspring hormone levels. Instead, sibling competition and poor parental care contributed to natural variation in stress responses. Parents with lower provisioning rates fledged fewer chicks, chicks from larger broods had elevated baseline CORT levels, and chicks with later hatching dates showed higher stress-induced CORT levels. Since CORT levels may influence the expression of adult neophobia, variation in juvenile stress responses could explain the development and maintenance of neophobic variation within the adult population.
... The found group differences support the notion that social environment can have a large influence on the behavior of individuals [Kralj-Fi ser et al., 2007;Sih & Bell, 2008]. Namely, it can both restrict the expression of behavioral traits through conformity and enhance them through facilitation [Webster & Ward, 2011], making the behavior of individuals of the same group more similar. ...
Article
Full-text available
The study of animal personality, defined as consistent inter-individual differences in correlated behavioral traits stable throughout time and/or contexts, has recently become one of the fastest growing areas in animal biology, with study species ranging from insects to non-human primates. The latter have, however, only occasionally been tested with standardized experiments. Instead their personality has usually been assessed using questionnaires. Therefore, this study aimed to test 21 common marmosets (Callithrix jacchus) living in three family groups, in five different experiments, and their corresponding controls. We found that behavioral differences between our animals were not only consistent over time, but also across different contexts. Moreover, the consistent behaviors formed a construct of four major non-social personality components: Boldness-Shyness in Foraging, Boldness-Shyness in Predation, Stress-Activity, and Exploration-Avoidance. We found no sex or age differences in these components, but our results did reveal differences in Exploration-Avoidance between the three family groups. As social environment can have a large influence on behavior of individuals, our results may suggest group-level similarity in personality (i.e., " group personality ") in common marmosets, a species living in highly cohesive social groups. Am. J. Primatol.
... Reactive individuals also tend to be more flexible and aware of environmental changes, whereas proactive individuals tend to be more rigid in their behaviour and easily form routines (e.g. mice, Mus musculus, Benus, den Daas, Koolhaas, & van Oortmerssen, 1990; pigs, Sus scrofa, Bolhuis, Schouten, de Leeuw, Schrama, & Wiegant, 2004;great tits, Carere, Drent, Privitera, Koolhaas, & Groothuis, 2005, greylag geese, Anser anser, Kralj-Fi ser, Scheiber, Blejec, Moestl, & Kotrschal, 2007). ...
Article
There is an increased focus in biology on consistent behavioural variation. Several terms are used to describe this variation, including animal personality and coping style. Both terms describe between-individual consistency in behavioural variation; however, they differ in the behavioural assays typically used, the expected distribution of response variables, and whether they incorporate variation in behavioural flexibility. Despite these differences, the terms are often used interchangeably. We conducted experiments using juvenile and adult red junglefowl, Gallus gallus, as subjects to explore the degree to which animal personality and coping styles overlap. We demonstrate that animal personality and coping styles can be described in this species, and that shyer individuals had more flexible responses, as expected for coping styles. Behavioural responses from both personality and coping style assays had continuous distributions, and were not clearly separated into two types. Behavioural traits were not correlated and, hence, there was no evidence of a behavioural syndrome. Further, behavioural responses obtained in personality assays did not correlate with those from coping style tests. Animal personality and coping styles are therefore not synonymous in the red junglefowl. We suggest that the terms animal personality and coping style are not equivalent and should not be used interchangeably.
... Inter-individual differences in aggression are usually demonstrated via observations of interactions between conspecifics (e.g. Huntingford, 1976;Francis, 1990;Verbeek et al., 1996;Garamszegi et al., 2006;Kralj-Fišer et al., 2007), but inter-individual differences in aggression towards heterospecifics have also been reported in several species (e.g. Huntingford, 1976;Budaev et al., 1999). ...
Article
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Animals in a population consistently differ from one another in behavioural types over time and this difference can affect intra- and interspecific relationships. However, empirical studies about roles of behavioural individual variation in interspecific interactions are scarce. Here, we provide evidence that inter-individual variation of a cichlid in aggression affects access to its territory by a heterospecific cichlid. In Lake Tanganyika, a zoobenthivorous cichlid Neolamprologus mustax (Nm) is admitted into territories of an algivorous Variabilichromis moorii (Vm) to prey on benthic invertebrates, while other zoobenthivorous fishes are chased from the territories. We conducted an experiment in which caged Nm fish were exposed twice to each Vm fish in natural habitats. Results indicated repeatable individual variations in Vm aggression towards Nm. Moreover, diving observations indicated that Nm fish frequently used some of Vm territories inside their own territories, but rarely or never used others. This uneven use of Vm territories by the Nm fish was negatively correlated with individual variations in Vm aggression. We conclude that the preferential access of Nm to Vm territory is gained by Nm’s recognising more tolerant Vm fish or discriminating among sites for their territories.
... Moreover, as is often the case in emergent disciplines, many studies fall into the trap of demonstrating behavioural syndromes as interesting in themselves, without any further adaptive explanation (e.g. Kortet and Hedrick, 2007, Kralj-Fiser et al., 2007, Svartberg et al., 2005. In the context of cooperative breeders, however, there are three non-mutually exclusive reasons for which one may predict behaviours to be consistent within individuals or correlated across contexts: mechanistic constraints, life-history trajectories and individual specialisation. ...
Thesis
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Individual variation in cooperation is a striking yet poorly understood feature of many animal societies, particularly in cooperative breeders where individuals assist in the care of young that are not their own. While previous research on these systems has emphasised the plasticity of helping and how it varies with current environmental and social conditions, in this dissertation I examine how individual variation is constrained and influenced by trade-offs with other behaviours and experiences in early life. I demonstrate that variation in cooperative pup care (babysitting and provisioning) is consistent within individuals over time (Chapter 3). Provisioning is more consistent than babysitting, although the two behaviours are highly correlated within individuals. I then focus on the variation in helping that remains once current factors, such as condition, group size and food availability, are taken into account. In Chapter 4, I explore the possibility that variation in helping can be explained by personality, or consistency in behavioural traits such as exploration or risk-taking. I find little evidence for consistent individual differences in field measures of personality traits, however, with such behaviours instead being group-specific. Early social experiences are known to have important and lasting effects on later fitness and behaviour: in Chapter 5, I demonstrate that, in female meerkats only, growing up in a group with more helpers is correlated with reduced cooperation later in life. This result suggests the importance of future fitness in influencing current cooperative behaviour, as females raised in larger groups are more likely to attain dominance. Finally, I examine the extent to which vocal communication between carers and young is influenced by variation in contributions to cooperation. Females are more sensitive to increased begging rate (Chapter 6), which reflects general sex differences in cooperative behaviour. Carers modify their vocalizations but not their foraging behaviour in the presence of pups, and the way in which they vocalize during provisioning events suggests these calls serve to increase efficiency of prey transfer (Chapter 7).
... The amount of variation in corticosterone responses raises questions about the consistency of responses in individual birds, and about the origins and significance of the individual differences. The consistency of responses (variation within individuals) has been examined in chickens, great tits and greylag geese (Anser anser), with responses of individual birds generally repeatable (Littin and Cockrem 2001;Cockrem and Silverin 2002a;Kralj-Fiser et al. 2007). Corticosterone responses of four great tits are shown in Fig. 3, illustrating how individual patterns of corticosterone response remained similar on the three sampling occasions in these birds. ...
... Therefore, repeated measures designs are necessary to quantify among-individual, i.e., repeatable, variation (Williams, 2008). The often mixed results on the topic of hormonal repeatability (Cockrem and Silverin, 2002b;Duckworth and Sockman, 2012;Jawor et al., 2006;Kralj-Fiser et al., 2007;Ouyang et al., 2011;Patterson et al., 2014;Rensel and Schoech, 2011;Romero and Reed, 2008;Vitousek et al., 2008;Wada et al., 2008;While et al., 2010), might be due in part to the fact that while some studies have based their inferences about individual-level processes on repeated measures data, others have not. Studies not using repeated measures designs and variance partitioning might be reporting unrepeatable (cf. ...
... There is some evidence to suggest that both hormone groups may remain consistent amongst individuals across periods of time, with males showing repeatability across days (fecal testosterone metabolites in sheep: Pelletier et al. 2003), months (fecal androgen and glucocorticoid metabolites in geese: Kralj-Fisher et al. 2007) and years (fecal cortisol but NOT androgen metabolties in red deer: Pavitt et al. 2015). Whilst these studies have primarily focussed on repeatability in males, While et al. (2010) also show circulating testosterone levels to be repeatable in both sexes of the lizard Egernia whitii over a several month time period. ...
Article
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Although hormones are key regulators of many fitness and life history traits, the causes of individual level variation in hormones, particularly in wild systems, remain understudied. Whilst we know that androgen and glucocorticoid levels vary within and among individuals in mammalian populations, how this relates to key reproductive processes such as gestation and lactation, and their effects on a female's measurable hormone levels are poorly understood in wild systems. Using fecal samples collected from females in a wild red deer population between 2001 and 2013, we explore how fecal androgen (FAM) and cortisol (FCM) metabolite concentrations change with age and season, and how individual differences relate to variation in reproductive state. Both FAM and FCM levels increase toward parturition, although this only affects FCM levels in older females. FCM levels are also higher when females suckle a male rather than a female calf, possibly due to the higher energetic costs of raising a son. This illustrates the importance of accounting for a female's life history and current reproductive status, as well as temporal variation, when examining individual differences in hormone levels. We discuss these findings in relation to other studies of mammalian systems and in particular to the relatively scarce information on variation in natural levels of hormones in wild populations.
... Individuals differ in suites of correlated behavioural and physiological characteristics ("personality", "behavioural syndrome", "coping style") leading to a cross-context consistency in how they deal with challenges (Gosling and John 1999, Sih et al. 2004, Kralj-Fiser et al. 2007. Behavioural phenotypes are genetically and epigenetically heritable (Dingemanse et al. 2002, Drent et al. 2003, Daisley et al. 2004) and they are one factor determining how an individual will respond to stress (reviewed in Cockrem 2007). ...
Research
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book chapter, on an experiment with Great tits of lines selected for fast and slow exploratory behaviour
... It is standard practise in physiological studies to take a single measurement from an individual and assume that it is representative of the sampled individual's phenotype [86]. A few studies have tested this assumption by determining the repeatability of glucocorticoid levels from multiple samples of the same individual and report individual consistency in basal glucocorticoid levels [59,73], stress-induced glucocorticoid levels [15,82], or both [14,45,56]. To our knowledge, repeatability of basal or stress-induced catecholamine levels has not been evaluated. ...
... Table 3 Variance components from two mixed-effect random regression models (data split between crabs exposed to no cues and crabs exposed to predator cues) testing for differences between individuals ("Individual ID") and for random slope variation across individuals between solitary and group settings ("Individual × Social context") blocked across trial Secondly, fluctuations in population density are a widespread response to changes in habitat quality (Heck and Wetstone 1977;Levin 1993;Warren et al. 2001;Goode et al. 2005;Gratwicke and Speight 2005;Cushman 2006), and likely produce similar behavioral shifts in other species since heightened individual boldness is a typical reaction to increases in conspecific density (Reebs 2000;Magnhagen and Staffan 2005;van Oers et al. 2005;Webster and Hart 2006;Webster et al. 2007;Magnhagen and Bunnefeld 2009;McDonald et al. 2016). However, as this and other studies have shown, not all individuals display the same level of behavioral plasticity across social context (van Oers et al. 2005;Kralj-Fišer et al. 2007;Magnhagen and Bunnefeld 2009;Oliveira 2009;McDonald et al. 2016). Such behavioral differences are important because they can govern how well individuals adapt to social and environmental changes. ...
Article
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Assessing the stability of animal personalities has become a major goal of behavioral ecologists. Most personality studies have utilized solitary individuals, but little is known on the extent that individuals retain their personality across ecologically relevant group settings. We conducted a field survey which determined that mud crabs, Panopeus herbstii, remain scattered as isolated individuals on degraded oyster reefs while high quality reefs can sustain high crab densities (>10 m(-2)). We examined the impact of these differences in social context on personality by quantifying the boldness of the same individual crabs when in isolation and in natural cohorts. Crabs were also exposed to either a treatment of predator cues or a control of no cue throughout the experiment to assess the strength of this behavioral reaction norm. Crabs were significantly bolder when in groups than as solitary individuals with predator cue treatments exhibiting severally reduced crab activity levels in comparison to corresponding treatments with no predator cues. Behavioral plasticity depended on the individual and was strongest in the presence of predator cues. While bold crabs largely maintained their personality in isolation and group settings, shy crabs would become substantially bolder when among conspecifics. These results imply that the shifts in crab boldness were a response to changes in perceived predation risk, and provide a mechanism for explaining variation in behavioral plasticity. Such findings suggest that habitat degradation may produce subpopulations with different behavioral patterns because of differing social interactions between individual animals.
... Although sociability is one of the major personality axes in animals (Réale et al. 2007), only a few studies have tested for and shown consistency in individuals' grouping tendencies (Kralj-Fišer et al. 2007;Gibbons et al. 2010;Cote et al. 2011). Likewise, network analysis techniques provide the potential for examining the ecological and evolutionary implications of sociability, but within-individual consistency in association patterns is rarely quantified (Wilson et al. 2013). ...
Article
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Personality and behavioral syndromes are of significant interest to a wide range of biological disciplines. Recent research using network analysis techniques has revealed widespread variation among individuals in sociability, which is a major axis of personality that creates the social microenvironment in which individuals express all other behaviors. We investigated the relationship between sociability and boldness, another fundamental personality axis, using a wild population of eastern grey kangaroos (Macropus giganteus) tested in their natural environment. We studied 2 dimensions of sociability (grouping behavior and association patterns). Over 2 years we found significant within-individual consistency and interindividual variation in the foraging group sizes of 171 females. Network analysis comparisons of 103 females between the years, using HWIG (an association index that controls for gregariousness), showed that individuals were also highly consistent in their social network measures. We tested the boldness of 51 of these females 6-21 times each over 18 months, using flight initiation distance tests; individuals were also highly consistent in this measure of personality. Shy females had significantly larger mean foraging group sizes. After controlling for gregariousness and space use, shy females had fewer preferred associates than bolder females. Therefore, boldness can have an important influence on the size and composition of foraging groups and thus social networks, in wild mammals.
... Subsequently, as new individuals immigrated and the population grew, variation among individuals in activity and aggression may have facilitated increases in population density in L. sclopetarius. The individual differences were stable over time with the repeatability estimates ranging from 0.43 to 0.49 for activity in a novel environment, and from 0.78 to 0.83 for aggressiveness, which is concordant with results from comparable invertebrate and vertebrate studies (Kralj-Fišer et al. 2007Pruitt et al. 2008;Bell et al. 2009). ...
Article
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Behavioral characteristics importantly shape an animals’ ability to adapt to changing conditions. The notion that behavioral flexibility facilitates exploitation of urban environments has received mixed support, but recent studies propose that between-individual differences are important. We leverage existing knowledge on three species of orb-web spider (Araneidae, Araneae) whose abundances differ along an urban–rural gradient to test predictions about between- and within-species/individual behavioral variation. We sampled Larinioides sclopetarius from their urban environment, and two species from suburban environments, Zygiella x-notata and Nuctenea umbratica. For each species, we quantified activity in a novel environment and within-species aggression. We analyzed between- and within-individual variation in behavior as well as their repeatability and correlations. As predicted, L. sclopetarius exhibited the highest activity in a novel environment and N. umbratica the lowest. Across all species, males were more aggressive than females and Z. x-notata was the most aggressive, followed by L. sclopetarius and N. umbratica. For all species, between-individual differences in activity and aggressiveness were repeatable; but the two behaviors were not correlated for any species. We next tested how group composition in relation to aggressiveness affects survival in high density conditions. Groups of Z. x-notata consisting of aggressive and tolerant spiders had higher survival rates than groups composed of only aggressive or tolerant individuals. Ultimately, we uncovered a complex pattern of behavioral variation between species as well as between and within individuals and we discuss the relative roles of this variation with respect to adapting to urban environments. Significance statement Urbanization has drastically changed biodiversity patterns. While the majority of species cope poorly with urban habitats, some species flourish in cities. Our understanding of behavioral characteristics that facilitate this exploitation, however, remains poor. We explored between and within species and individual variation in behaviors in ecologically similar orb-weaving spider species whose abundances differ along the urban–rural gradient. We detect both consistent individual differences and plasticity, in individuals’ response to a novel environment, suggesting that some degree of flexibility in reaction to novelty may be crucial in an urbanized environment. We also found that variation in aggressiveness type enables survival in high density conditions, conditions typical for urban populations. Urban populations thus exhibit a complex pattern of behavioral flexibility and behavioral stability.
... Moreover, as is often the case in emergent disciplines, many studies fall into the trap of demonstrating behavioural syndromes as interesting in themselves, without any further adaptive explanation (e.g. Kortet and Hedrick, 2007, Kralj-Fiser et al., 2007, Svartberg et al., 2005. In the context of cooperative breeders, however, there are three non-mutually exclusive reasons for which one may predict behaviours to be consistent within individuals or correlated across contexts: mechanistic constraints, life-history trajectories and individual specialisation. ...
Article
Individual variation in cooperation is a striking yet poorly understood feature of many animal societies, particularly in cooperative breeders where individuals assist in the care of young that are not their own. While previous research on these systems has emphasised the plasticity of helping and how it varies with current environmental and social conditions, in this dissertation I examine how individual variation is constrained and influenced by trade-offs with other behaviours and experiences in early life. I demonstrate that variation in cooperative pup care (babysitting and provisioning) is consistent within individuals over time (Chapter 3). Provisioning is more consistent than babysitting, although the two behaviours are highly correlated within individuals. I then focus on the variation in helping that remains once current factors, such as condition, group size and food availability, are taken into account. In Chapter 4, I explore the possibility that variation in helping can be explained by personality, or consistency in behavioural traits such as exploration or risk-taking. I find little evidence for consistent individual differences in field measures of personality traits, however, with such behaviours instead being group-specific. Early social experiences are known to have important and lasting effects on later fitness and behaviour: in Chapter 5, I demonstrate that, in female meerkats only, growing up in a group with more helpers is correlated with reduced cooperation later in life. This result suggests the importance of future fitness in influencing current cooperative behaviour, as females raised in larger groups are more likely to attain dominance. Finally, I examine the extent to which vocal communication between carers and young is influenced by variation in contributions to cooperation. Females are more sensitive to increased begging rate (Chapter 6), which reflects general sex differences in cooperative behaviour. Carers modify their vocalizations but not their foraging behaviour in the presence of pups, and the way in which they vocalize during provisioning events suggests these calls serve to increase efficiency of prey transfer (Chapter 7).
... The aim of this chapter is to provide a broad overview of studies on avian personality, including those that address genetic variation linked to personality (Van Oers et al. 2005a;Fidler et al. 2007;Gil and Faure 2007;Bell and Aubin-Horth 2010;Van Oers and Muller 2010), the behavioral and fi tness consequences of personality in natural populations (e.g., ; Dinge manse and Wolf 2010; Wolf and Weissing 2010), mathematical models that investigate possible scenarios for the evolution of personality (Wolf et al. 2007;Amy et al. 2010;Dingemanse and Wolf 2010;Houston 2010), and the physiological substrate of personality (e.g., Carere et al. 2005a;Kralj-Fiser et al. 2007;Fucikova et al. 2009;Coppens et al. 2010;Baugh et al. 2012). We also provide a historical background of personality research in birds and discuss recent studies from a historical perspective. ...
Chapter
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... If slight biases in physiological regulation are relatively stable traits within an individual (e.g. [67][68][69][70][71][72][73][74]), then these may support or drive the relative stability, covariance and fitness of behavioural traits [39,70]. To this end, there is already strong evidence that behavioural variance among individuals is systematically associated with neuroendocrine variance (reviewed below) [25,37,48,75]. ...
Article
Animal behaviour research has experienced a renewed interest in consistent individual differences (i.e. animal personality or temperament). Recent ecological studies have identified environmental conditions that give rise to the development and evolution of temperaments and to fitness-related outcomes of temperament. Additional literature has also described relationships between temperaments and physiological regulation. However, one-to-one relationships between one behavioural trait and one physiological system do not account for co-selection of behavioural and physiological traits, nor the complex signalling among physiological systems. In the current paper, we review the literature on multiple physiological processes associated with temperament, propose temperament-specific physiological profiles, and focus on next steps to understand the functional significance, evolution and maintenance of temperaments. We propose that to understand causes and consequences of temperament we need to characterize integrative physiological profiles associated with different temperaments.
... In addition to these theoretical links between personality and intraspecific aggression, there is increasing empirical evidence that aggressiveness, the propensity to initiate, escalate, or persist in an agonistic encounter, can be a personality trait. In insects (Clark and Moore 1995;Brown et al. 2006) and vertebrates (Bakker 1986;Riddell and Swain 1991;Garamszegi et al. 2006;Kralj-Fiser et al. 2007;Pavlova et al. 2007;Wilson et al. 2011Wilson et al. , 2013, for example, some individuals are consistently more aggressive than others. Consistent aggressiveness may also extend beyond the context of intraspecific contests to interspecific conflict as in the case of aggression directed toward brood parasites (Trnka et al. 2013). ...
Article
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Consistent between-individual differences in behavior have been demonstrated in an array of species from diverse taxa, and variation in boldness may be associated with variation in aggressiveness. However, little is known about how boldness is linked with the ability to win fights (resource holding potential) or about how the experience of fighting may alter subsequent boldness. Animal contests often involve role asymmetries, where the 2 opponents fight in different ways. Here, we investigate boldness before and after fighting in attacking and defending hermit crabs during contests over the ownership of gastropod shells. Although prefight boldness did not influence the chance of winning for attackers, successful defenders had longer startle responses (less bold) than those that gave up. Postfight changes in boldness also differed between roles. For defenders, there was a significant decline in consistency of startle responses after fighting, coupled with outcome-dependent plasticity in mean boldness. Furthermore, postfight boldness in defenders varied with the intensity of agonistic behavior inflicted on them by attackers. In contrast, boldness in attackers was stable across the before-and after-fighting situations. Links between internal state and agonistic behavior are known to vary between roles in asymmetric contests. It now appears that similar role-specific links are present between aggression and animal personality.
... Hence, data may be analysed as group behaviour, when in fact an animal may be alone, which may lead to an inaccurate interpretation of group behaviour. Because it is usually prohibitively expensive to equip entire populations with satellite-or global positioning system (GPS)-tracking technology, assumptions on species' movement ecology are generally based on data from a relatively small number of individuals (Kralj-Fišer et al. 2007, Lindsell et al. 2009, Schorr et al. 2009, Hauser et al. 2014. Sample size and tracking period are important factors, and may not be of an appropriate size to make assumptions at the population level, particularly with reference to home range or spatial distribution of the species (Thaxter et al. 2017). ...
Thesis
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Historically it has been difficult to gain information on the movement ecology of psittacine species in Australia. Using a novel double-tagging telemetry method, this research, aimed to: investigate regional differences in movement of the three black cockatoo species endemic to Western Australia; identify key roost and foraging sites for these species across regions; and estimate home range sizes for flocks in resident areas, using a combination of GPS and satellite PTT tags. Tagged birds served as markers of flock movement once integrated into a wild flock of conspecifics, which was confirmed through means of behavioural change point analysis and field observations. Linear mixed models were used to determine differences in movement across regions, revisitation analysis was used to identify key habitat sites, and an auto-corrected Kernel density estimator was used to estimate the home ranges. Results showed that key roosts sites for the three species predominantly occurred on public green space and private property. These were closely associated with foraging habitat which mainly occurred as remnant vegetation in the landscape or as nature reserves. Riparian zones and roadside vegetation were shown to play a crucial role as foraging habitat and in providing connective landscape structures. Daily movement distances differed both between and within regions depending on habitat matrix, resulting in varying home range sizes. These results suggest that movement for the three black cockatoo species is region specific, driven by food resources in the landscape. In addition, between species, movement varied as each species uses the landscape in different ways, depending on seasonal movements and ecological requirements. This research has provided critical baseline data required to address knowledge gaps listed in Recovery Plans for these species of black cockatoo. Further research is now required to include these data in resource and habitat selection models to identify how the landscape matrix affects movement, which will facilitate adaptive habitat management and conservation plans for black cockatoos in Western Australia.
... While some studies report repeatabilities for hormonal traits (e.g. Angelier et al., 2010;Beletsky, 1992;Kralj-Fišer et al., 2007;Narayan et al., 2013;While et al., 2010), others fail to detect any repeatability (e.g. Rensel and Schoech, 2011;Romero and Reed, 2008;Vitousek et al., 2008). ...
Article
Consistent between-individual differences in behaviour have been documented across the animal kingdom. Such variation between individuals has been shown to be the basis for selection and to act as a pacemaker for evolutionary change. Recently, equivocal evidence suggests that such consistent between-individual variation is also present in hormones. This observation has sparked interest in understanding the mechanisms shaping individual differences, temporal consistency and heritability of hormonal phenotypes and to understand, if and to what extent hormonal mechanisms are involved in mediating consistent variation in behaviour between individuals. Here, we used zebra finches of the fourth generation of bi-directionally selected lines for three independent behaviours: aggression, exploration and fearlessness. We investigated how these behaviours responded to artificial selection and tested their repeatability. We further tested for repeatability of corticosterone and testosterone across and within lines. Moreover, we are presenting the decomposed variance components for within-individual variance (i.e. flexibility) and between-individual variance (i.e. more or less pronounced differences between individuals) and investigate their contribution to repeatability estimates. Both hormones as well as the exploration and fearlessness but not aggressiveness, were repeatable. However, variance components and hence repeatability differed between lines and were often lower than in unselected control animals, mainly because of a reduction in between-individual variance. Our data show that artificial selection (including active selection and genetic drift) can affect the mean and variance of traits. We stress the importance for understanding how variable a trait is both between and within individuals to assess the selective value of a trait.
... changes in hormone secretion, hormonal affinity for carrier proteins, rates of degradation and conversion, and interaction with target tissues) could potentially coordinate the co-expression of behavioural, physiological and morphological traits leading to covariation (hormonal pleiotropy sensu (35)). In particular, corticosterone (CORT hereafter), a glucocorticoid widely investigated in birds that affects the response to stress through the activation of hypothalamus-pituitary-adrenal (HPA) axis, might play such a modulator role since it has been profusely linked with behaviour (36)(37)(38)(39) and melanism (40)(41)(42). Whichever the exact mechanism promoting covariation between phaeomelanin pigment and other traits, which is far of our scope here, very few studies have yet analyses how phaeo-rather than eu-melanin colorations integrate with other phenotypic characters. ...
Preprint
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Background: Individuals within populations often show consistent variation in behavioural and physiological traits, which are frequently inter-correlated, potentially leading to phenotypic integration. Understanding the mechanisms behind such integration is a key task in evolutionary ecology, and melanism has been suggested to play a pivotal role. In birds, most of plumage colour variation is determined by two types of melanin, eumelanin and phaeomelanin, but the role of melanin in avian phenotype integration has mostly been analysed in relation to eumelanin. Here we test for covariation between phaeo-melanin-based coloration, behavioural traits (i.e. nest territoriality, response against researchers, breath rate and parental behaviour) and corticosterone profiles in the polymorphic scops owl Otus scops , a bird species in which more phaeomelanic individuals display reddish colorations. Results: In males, we observed differences between red and grey individuals in latency to return to the nest after being disturbed and in feather CORT. Reddish males took longer to return to their nests and showed higher levels of feather CORT than grey ones. Behaviour and CORT profiles did not differ between red and grey females. Conclusions: The found associations between redness, behaviour and CORT in males, but not in females, might suggest the existence of a sex-specific integrated phaeomelanic phenotype, likely due to pleiotropy, in scops owls.
... To improve our interpretations of among-individual variation in hormone concentrations, information about within-individual variation is needed (Schoenemann and Bonier, 2018). The repeatability of hormones has been extensively studied with no conclusive agreement about (co)variation (Cockrem and Silverin, 2002;Love et al., 2003;Kralj-Fiser et al., 2007;Cockrem et al., 2009;Ouyang et al., 2011;Rensel and Schoech, 2011). For example, Grace and Anderson (2014) found repeatability of stress-induced GCs in the Nazca booby (Sula granti) measured over multiple years, while Baugh et al. (2014) found no repeatability in stress-induced GCs in great tits (Parus major) measured within one season. ...
Article
There is a renewed interest in investigating individual variation in hormone levels in relation to fitness metrics, as hormones act as mediators of life-history trade-offs. Hormone concentrations, however, are labile, responding to both internal and external stimuli, so the relationship between hormones and fitness can be non-consistent. One explanation of this inconsistent relationship is that a single hormone sample may not be representative of individual phenotypes in a free-living species. We addressed this issue by repeatedly sampling a free-living population of mountain white-crowned sparrows, Zonotrichia leucophrys oriantha, for baseline and stress-induced corticosterone (cort) and testosterone (T) across different stages of the breeding season. We measured (co)variation using three different methods, taking into account inter- and intra-individual variances, to determine whether hormone levels and the stress response are repeatable. We documented the temporal (over 3 months) and spatial (home-range) variation of individual hormone phenotypes and investigated how these components related to nesting success. At the population level, we found significant repeatability in male stress-induced cort concentrations but no repeatability in male or female baseline cort or male T concentrations. Using a new metric of intra-individual variance focusing on the stress response (profile repeatability), we found a wide range of variance scores, with most individuals showing high variation in their stress response. Similarly, we found a low level of repeatability of the reaction norm intercept and slope for the stress response across different life-history stages. Males with higher concentrations of stress-induced cort had more central home-ranges. Males with higher body condition had larger home-ranges; however, home-range size did not relate to male hormone concentrations or nesting success. We also did not find any significant relationship between variation in hormone levels and nesting success. We recommend that future studies combine both physiological and environmental components to better understand the relationship between hormones and fitness.
... Second, Alison et al. [75] found that animal activity is inherently less repetitive than other behaviors. Moreover, some studies have found that animal activity is not repetitive [84,85]. Thus, it may be reasonable that bats' activity did not show repeatability. ...
Article
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Personality traits represent a leading edge in the evolutionary process, as natural selection acts directly on variations in individual phenotypes within populations. Recent theoretical models have focused on the concept of adaptive state-dependent behavior, proposing that repeatable differences in behavior emerge because of individual differences in repeatable state variables, such as metabolic rate, age, sex, or body size. Personality and its correlation with body size, however, have been relatively unexplored in bats. We used female Asian particolored bats (Vespertilio sinensis) to investigate three personality characteristics (exploration, activity, and aggression) using the classic hole-board test and examined their relationships with body size using an information-theoretical approach. Our results showed that the exploration of female Asian particolored bats was significantly repeatable, but we did not find significant correlations among the three personality traits. This finding suggested that the female Asian particolored bat may not have a behavioral syndrome. In addition, the body mass of female Asian particolored bats was positively correlated with aggression but was negatively correlated with activity, suggesting that body mass was an important physiological basis affecting the behavioral characteristics of female Asian particolored bats.
... These estimates vary depending on the time lag between repeat measures and the specific aspect of GC secretion that is measured -i.e. basal secretion, secretion in response to a stressor, circadian rhythm/slope, total secretion over hours or months, etc. (Cavigelli et al., 2009;Cockrem, 2013;Cockrem et al., 2009;Cockrem and Silverin, 2002;Kralj-Fišer et al., 2007;Ross et al., 2014;Taff et al., 2018;Wada et al., 2008). Although the data are relatively limited because of the difficulty in measuring circulating GC hormones in a consistent manner within the same individual over time (e.g. ...
Article
Glucocorticoid (GC) signaling varies among individuals, and this variation may relate to individual differences in health outcomes. To determine if and which aspects of signaling (basal, circadian, integrative, or reactivity) are associated with specific health outcomes, we reviewed recent studies that relate GCs to health outcomes. We identified papers through PubMed and reviewed 100 original research articles related to mental health, cardiovascular health, cancer, diabetes, obesity, pulmonary health, sleep, and fitness. Many studies reported elevated GC secretion associated with worse health, but this was only particularly true for integrative GC measures. On the other hand, accentuated cortisol awakening response and a steeper circadian rhythm were both associated with positive health outcomes. Overall, relationships between GC secretion and health outcomes were relatively weak. This systematic review of relationships between GC metrics and health outcomes highlights the importance of careful consideration when selecting methods to measure GC regulation in health research.
... Whereas several studies demonstrated correlations between various personality traits and responses to an acute stressor (e.g. Korte et al. 1992;Carere et al. 2003;Kralj-Fišer et al. 2007), others found that individuals with proactive personality traits had the highest HPA response to a stressor (e.g. Martins et al. 2007;Boulton et al. 2015), suggesting a non-linear connection between coping styles and HPA axis activity and reactivity (Koolhaas et al. 2010). ...
Article
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Between-individual differences in coping with stress encompass neurophysiological, cognitive and behavioural reactions. The coping style model proposes two alternative response patterns to challenges that integrate these types of reactions. The “proactive strategy” combines a general fight-or-flight response and inflexibility in learning with a relatively low HPA (hypothalamic–pituitary–adrenal) response. The “reactive strategy” includes risk aversion, flexibility in learning and an enhanced HPA response. Although numerous studies have investigated the possible covariance of cognitive, behavioural and physiological responses, findings are still mixed. In the present study, we tested the predictions of the coping style model in an unselected population of bank voles (Myodes glareolus) (N = 70). We measured the voles’ boldness, activity, speed and flexibility in learning and faecal corticosterone metabolite levels under three conditions (holding in indoor cages, in outdoor enclosures and during open field test). Individuals were moderately consistent in their HPA response across situations. Proactive voles had significantly lower corticosterone levels than reactive conspecifics in indoor and outdoor conditions. However, we could not find any co-variation between cognitive and behavioural traits and corticosterone levels in the open field test. Our results partially support the original coping style model but suggest a more complex relationship between cognitive, behavioural and endocrine responses than was initially proposed. Significance statement Understanding the proximate mechanisms regulating the individual variation in responses to environmental challenges and changes is fundamental in ecological and evolutionary research. Theory predicts correlations between behavioural, cognitive and physiological traits to form alternative strategies named coping styles but recent studies report contrasting and mixed findings. We examined the relationship between a measure of endocrine state (concentrations of faecal glucocorticoid metabolites), two behavioural traits (boldness and activity) and two cognitive traits (speed and flexibility of learning) in 70 unselected bank voles (Myodes glareolus) under three different conditions. The findings partially support the original coping style model’s hypothesis and predictions. We found individual consistency of all traits. However, correlations between behavioural and cognitive aspects and endocrine state were found only in two of the three tested conditions, highlighting the need for further investigations and testing of theory.
... BI individuals also show elevated basal glucocorticoid production [58,100,104,8] which has been associated with negative health and immune outcomes (summarized in [24,79,114,88]). In animals, BI/neophobia/exploration (defined by approach latency, locomotion, and/or time interacting with novel objects) are relatively stable traits over time and across contexts [111,115,31,19,73,20,63,10,18]. Like in humans, BI male rats, defined as having consistently slower-than-median approach latencies in two novel conditions, have low-grade elevation in glucocorticoid production which is associated with shortened life span [19,20,22]. ...
... Under the concept of phenotypic integration (Foster et al. 1992) or the existence of behavioural syndromes (Sih et al. 2004), we would expect a correlation between behaviours expressed during courtship and behaviours expressed during parental care. This is because functionally different behaviours could be governed by common genetic (Bakker 1986;van Oers et al. 2004) or physiological proximate mechanisms (Carere et al. 2003;Kralj-Fišer et al. 2007). In addition, if courtship and parental behaviour utilise the same limiting resources and are therefore traded off against each other (Stearns 1989), a correlation between these behaviours can be apparent. ...
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Individuals of many animal species show consistent differences in ecologically relevant behaviours, and these individual-specific behaviours can correlate with each other. In passerines, aggression during nest-site defence is one of those behaviours that have been steadily found to be repeatable within individuals. Furthermore, in several cases, aggression was related to some estimates of reproductive investment. Here, we studied the possibility that behaviour of males toward a male rival predicts the amount of their future parental care. This could be beneficial to the females, because during mate choice, they could use male aggressive behaviour as a cue for parental quality. We performed the study by video recording the nestling feeding activity of male collared flycatchers (Ficedula albicollis) that were assayed for aggression during the courtship period. The level of aggression was not related to feeding rate in males. Feeding rate of males differed between the study years, but it did not correlate with the feeding rate of their mates, neither was it related to the morphological traits of the parents. We may conclude that nest-site defence aggression of males does not predict their parental commitment. This may be surprising given that higher testosterone levels that may be expected in aggressive males often suppress parental care. However, among-individual variance in male testosterone profiles found to be decrease from the courtship to the parenting period in flycatchers, and this may explain why differences in territorial aggression did not manifest in differences in nestling provisioning. The correlation between behaviours that are expressed in distinct periods of the annual cycle of songbirds needs further investigation. Significance statement Male songbirds, when attracting mates, are often confronted with each other over nest-sites, and these male-male confrontations may be witnessed by females. If performance during territory defence predicts the quality of parental care that a male will provide for its nestlings, females could use defence behaviour as a cue for mate choice. To explore this possibility, we investigated the relationship between territorial aggression and nestling feeding activity of male collared flycatchers. We performed simulated territorial intrusions to measure the aggression of males and recorded their nestling feeding rate about a month later. We found that territorial aggression did not correlate with nestling feeding rate. This suggests that nest-site defence behaviour in the beginning of the breeding season does not carry information for females about what to expect from potential mates in terms of parental care.
... Hence, data may be analyzed as group behavior, when in fact an animal may be alone, which may lead to an inaccurate interpretation of group behavior. Because it is usually prohibitively expensive to equip entire populations with satellite-or global positioning system (GPS)-tracking technology, assumptions on species' movement ecology are generally based on data from a relatively small number of individuals (Kralj-Fi ser et al. 2007, Lindsell et al. 2009, Schorr et al. 2009, Hauser et al. 2014. Sample size and tracking period are important factors, and may not be of an appropriate size to make assumptions at the population level, particularly with reference to home range or spatial distribution of the species (Thaxter et al. 2017). ...
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Establishing integration of an individual bird into a wild flock is particularly important in species that are highly gregarious and are reliant on the flock to increase their likelihood of survivorship. When individuals, rehabilitated and reintroduced to wild flocks, are tracked through satellite or global positioning system (GPS) telemetry, it is of further significance to establish integration to assess rehabilitation success and whether the individual can serve as a marker of the flock. To date, for black cockatoos (Calyptorhynchus spp.) this has been achieved through visual observations, which requires fieldbased observations that may not be possible because of inaccessible terrain, or may be untenable because the tagged individual can move quickly or is cryptic within a given land cover type. To establish whether an individual had joined a flock, we proposed the use of behavioral change point analysis. Our analyses showed that for GPS data of 6 individuals of the 3 black cockatoo species endemic to Western Australia we could demonstrate behavioral differences in their movement paths that were either individual or flocked (integrated) behavior. We undertook field observations to validate integration into wild flocks. We characterized flocked behavior as a constant, repeated pattern at variable levels of velocity. Individual behavior manifested in 2 different forms: resident and exploratory behavior. The analysis showed that all birds had integrated into a wild flock within a month of release. Behavioral change point analysis is a useful method to characterize movement behavior in black cockatoos and to confirm their membership within a flock. Furthermore, confirmation of flock membership makes it possible to use the data from 1 tagged bird to indicate movement behavior at the flock level.
... In zebra finches (Poephila guttata), increased corticosterone levels after a stressful experience produced greater exploration and risk-taking behavior (Martins et al., 2007). In male greylag geese, individuals' baseline levels of corticosterone metabolite and testosterone were found to be consistent across contexts of feeding and handling (antipredation), which may be partly responsible for maintaining personality traits in the geese (Kralj-Fiser et al., 2007). ...
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This study investigated bold-shy personality in the budgerigar, Melopsittacus undulatus. Adult budgerigars (14 females, 9 males) fed either a control diet, or one supplemented with docosahexaenoic acid (DHA), were subjected to seven behavioral tests and two immunocompetence assays. Behavioral responses were categorized by context: fear, feeding, or activity. Correlations were obtained within contexts and among immunocompetence variables and all behavioral variables. Kruskal-Wallis analysis was used to investigate effects of gender and DHA on all variables. Budgerigars behaved consistently within activity and feeding contexts. Males had higher feeding rates, and their feeding responses were negatively correlated with a measure of innate immunity. Cluster analysis characterized birds by activity levels; bold birds were highly active and shy birds were less active. The results of this study suggest that budgerigars exhibit consistent behaviors in two contexts, feeding and activity, which are unrelated to each other, and that activity is the predominant personality trait.
... The unexpected strong negative correlation between NAV victimization and time between disturbance and sampling suggest that early-life maltreatment also affects behaviour, a hypothesis supported by correlations between early-life maltreatment experience and later-life maltreatment behaviour in this species [5]. Longer times to sample resulted from stronger resistance to handling, which is highly repeatable in other species [26,27]. Maltreatment thus appears to be correlated with both hormonal and behavioural response to later-life stress, although further research is needed. ...
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Persistent phenotypic changes due to early-life stressors are widely acknowledged, but their relevance for wild, free-living animals is poorly understood. We evaluated effects of two natural stressors experienced when young (maltreatment by adults and nutritional stress) on stress physiology in wild Nazca boobies (Sula granti) 6-8 years later, an exceptionally long interval for such studies. Maltreatment as a nestling, but not nutritional stress, was associated years later with depressed baseline corticosterone in females and elevated stress-induced corticosterone concentration [CORT] in males. These results provide rare evidence of long-term hormonal effects of natural early-life stress, which may be adaptive mechanisms for dealing with future stressors.
... Recently, within and between individual consistency in behaviour across time and contexts have been shown to be more common than previously thought , and have led to assume that personalities or temperaments may be found in animals. Personality has been shown to possibly vary with age and sex (English et al. 2010), and to shape a wide range of behaviours from aggression (Kralj-Fiser et al. 2007) and exploratory behaviour to courtship (Forstmeier & Birkhead 2004) . ...
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Predation can have very important effects on both the ecology and evolution of biological communities. In particular predation may impose a strong selection pressure for more efficient predators and less vulnerable prey. In addition, more and more evidence show that predators affect prey not only directly by killing them, but that they can also influence their behaviour and induce morphological and physiological responses. Yet today, little is known about how predators limit prey populations, especially in large herbivores. The most detailed studies on large herbivores are indeed located in the northern hemisphere, often in places where these herbivores have no predators. In this thesis I have studied a population of large herbivores and the impact of predation on it: the population of plains zebras (Equus quagga) in Hwange National Park in Zimbabwe and their interaction with the lions. I studied the dynamics of populations of zebras in our study area, but I also studied zebra behaviour at the individual level, trying to understand the anti-predator behaviours used by zebras and what their potential costs were, focusing on individual differences. This population of zebras was strongly impacted by predation, indirectly as well as directly, and the anti-predator behaviours were costly.
... Androgens such as testosterone have long been associated with behaviour (Carere, Groothuis, M€ ostl, Daan, & Koolhaas, 2003;Koolhaas et al., 1999;Kralj-Fi ser, Scheiber, Blejec, Moestl, & Kotrschal, 2007;Sellers, Mehl, & Josephs, 2007), for example, mediating aggression, reproduction and agonistic interactions in birds (Klein, 2000;Partecke & Schwabl, 2008;Wingfield, Ball, Dufty, Hegner, & Ramenofsky, 1987). Research suggests that positive associations between androgens and aggression may also involve heightened hypothalamicepituitaryeadrenal (HPA)-axis activity and elevated glucocorticoid levels, as they can be correlated (Liptrap & Raeside, 1978). ...
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Animal behaviours, like aggression, can directly affect host health by influencing exposure to parasites. Aggressive individuals may experience an increase in agonistic interactions and contact rates with conspecifics, which might increase their probability of acquiring parasites. However, aggression is not the only factor that shapes parasitism; proximate mechanisms like hormone-modulated immunosuppression can also have broad impacts. Here, we hypothesized that high levels of aggression, cortisol and testosterone would be positively associated with parasitism and that aggressive individuals would play a larger role spreading parasites to conspecifics than would docile individuals. We measured aggression using the level of aggressive response to human handling during capture. Our aim was to examine associations between aggression and hormones (cortisol and testosterone) on variation in endo-and ectoparasitism in a population of wild mouse lemurs (Microcebus rufus) over a 3-year period. By tracking the movement of lice (directly transmitted parasites) in the population, we also examined the effect of host aggression on population-wide parasite dynamics. We show that animals with high testosterone and cortisol were more likely to exhibit aggressive behaviours, and cortisol was associated with significantly higher ectoparasite infestations. Aggressive individuals were significantly more infested by lice, and also donated significantly more lice to conspecifics in the population. Taken together, our results offer insight into the individual and population health costs of aggression, and empirical support of a trade-off between aggression and ectoparasitism, which may have driven the evolution of aggression and interactions with conspecifics.
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Investigating the proximate mechanism underlying behavior has long been a primary goal of ethologists. With the recent focus on behavioral correlations (e.g., behavioral syndromes), a fundamental question arises regarding what mechanisms may drive positive relationships between functionally distinct behaviors. Understanding these mechanisms can inform critical questions, such as why distinct behaviors are often correlated, and can also lend insights into how behavioral similarities are conserved across species. Arthropods provide an idea system to study these questions as the biogenic amines, such as octopamine and serotonin, have long been known to mediate a large number of behaviors such as aggression, dominance, escape behavior, and others. Behaviorists have several ways in which they can manipulate these biogenic amines in vivo, including injection, feeding, and topical application. Topical application is potentially an optimal method for manipulating amine concentrations, given that it is minimally invasive and relatively precise. Here, we investigate the role of biogenic amines, octopamine, and serotonin, in mediating a range of similar and often correlated behaviors in two distantly related species of spiders, the western black widow, Latrodectus hesperus, and the funnel-web spider, Agelenopsis pennsylvanica. Additionally, we investigate the behavioral effects associated with three commonly used carrier solvents: dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and acetone. We demonstrate that biogenic amines are involved both in mediating several behaviors, and also potentially the links between different behaviors. We also show that the same behaviors in different species are not affected by biogenic amines in the same manner, suggesting differences in the underlying neurophysiological mechanisms governing behavior. Furthermore, we discovered large and pervasive effects associated with both carrier solvents, thus calling into question the potential usefulness and interpretability of topical application methods in behavioral research.
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Within species, individuals often show repeatable differences in behaviours, called ‘animal personality’. One behaviour that has been widely studied is how quickly an individual resumes feeding after a disturbance, referred to as boldness or risk-taking. Depending on the mechanism(s) shaping risk-taking behaviour, risk-taking could be positively, negatively, or not associated with differences in overall survival. We studied risk-taking and survival in a population of free-living black-capped chickadees ( Poecile atricapillus ) in which we previously showed repeatable among-individual differences in risk-taking over the course of several months. We found no evidence that variation in risk-taking is associated with differences in annual survival. We suggest that variation in risk-taking is likely shaped by multiple mechanisms simultaneously, such that the net effect on survival is small or null. For example, among-individual differences in energy demand may favour greater risk-taking without imposing an overall mortality cost if higher energy demand covaries with escape flight performance. We propose directions for future work, including using a multi-trait, multi-year approach to study risk-taking, to allow for stronger inferences regarding the mechanisms shaping these behavioural decisions.
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The early social environment can profoundly affect behavioral and physiological phenotypes. We investigated how male wild cavy offspring, whose mothers had either lived in a stable (SE) or an unstable social environment (UE) during pregnancy and lactation, differed in their anxiety-like behavior and stress responsiveness. At two different time points in life, we tested the offspring's anxiety-like behavior in a dark-light test and their endocrine reaction to challenge in a cortisol reactivity test. Furthermore, we analyzed whether individual traits remained stable over time. There was no effect of the early social environment on anxiety-like behavior and stress responsiveness. However, at an individual level, anxiety-like behavior was stable over time in UE- but not in SE-sons. Stress responsiveness, in turn, was rather inconsistent in UE-sons and temporally stable in SE-sons. Conclusively, we showed for the first time that the early social environment differentially shapes the stability of behavioral and endocrine traits. At first glance, these results may be surprising, but they can be explained by the different functions anxiety-like behavior and stress responsiveness have.
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Individuals vary in their behavioral and physiological responses to environmental changes. These behavioral responses are often described as ‘coping styles’ along a proactive-reactive continuum. Studies in laboratory populations often, but not always, find that behavioral responses and physiological responses to stressors covary, where more proactive (more aggressive and active) individuals have a lower physiological stress response, specifically as measured by hypothalamic-pituitary-adrenal (HPA) axis activity. These studies support the possibility of hormonal pleiotropy underlying the presentation of behaviors that make up the proactive-reactive phenotype. However, recent research in wild populations is equivocal, with some studies reporting the same pattern as found in many controlled laboratory studies, whereas others do not. We tested the hypothesis that physiological and behavioral stress responses are correlated in wild adult North American red squirrels ( Tamiasciurus hudsonicus ). We used fecal cortisol metabolites (FCMs) as a non-invasive, integrated estimate of circulating glucocorticoids for our measurement of HPA axis activity. We found that FCM concentrations were not correlated with three measures of behavioral coping styles (activity, aggression, and docility) among individuals. This does not support the hypothesis that hormonal pleiotropy underlies a proactive-reactive continuum of coping styles. Instead, our results support the “two-tier” hypothesis that behavioral and physiological stress responses are independent and uncorrelated traits among individuals in wild populations that experience naturally varying environments rather than controlled environments. If also found in other studies, this may alter our predictions about the evolutionary consequences of behavioral and endocrine coping styles in free-living animals. Significance Statement Individuals vary in how they respond to stressors through behavior and physiology, but we find the two responses are independent in wild animals. Many laboratory studies find links between the behavioral and physiological stress responses, however studies conducted with wild populations are less conclusive. In wild North American red squirrels, independence between the physiological response and behavioral response may allow adaptive responses to a changing environment without pleiotropic constraint.
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Individuals within populations often show consistent variation in behavioural and physiological traits which are frequently inter-correlated, potentially leading to phenotypic integration. Understanding the mechanisms behind such integration is a key task in evolutionary ecology, and melanin based colouration has been suggested to play a pivotal role. In birds, most of plumage colour variation is determined by two types of melanin, eumelanin and phaeomelanin, but the role of phaeomelanin in avian phenotype integration has been barely investigated. Here, we test for covariation between phaeomelanin-based colouration, behavioural traits (i.e. nest territoriality, aggressiveness, breath rate and parental behaviour) and corticosterone in feathers in the polymorphic scops owl Otus scops , a bird species in which more phaeomelanic individuals display reddish colourations. In males, we observed that reddish males took longer to return to their nests and showed higher levels of feather CORT than more greyish ones. Behaviour and feather CORT were not associated to plumage colour in females. The found associations between redness, behaviour and feather CORT in males, but not in females, might suggest the existence of a sex-specific integrated phaeomelanic phenotype in scops owls.
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Humans currently occupy all continents and by doing so, modify the environment and create novel threats to many species; a phenomenon known as human-induced rapid environmental changes (HIREC). These growing anthropogenic disturbances represent major and relatively new environmental challenges for many animals, and invariably alter selection on traits adapted to previous environments. Those species that survive often have moved from their original habitat or modified their phenotype through plasticity or genetic evolution. Based on the most recent advances in this research area, we predict that wild individuals with highly plastic capacities, relatively high basal stress level, and that are generally shy-in other words, individuals displaying a reactive phenotype-should better cope with sudden and widespread HIREC than their counterparts' proactive phenotypes. If true, this selective response would have profound ecological and evolutionary consequences and can therefore impact conservation strategies, specifically with respect to managing the distribution and abundance of individuals and maintaining evolutionary potential. These insights may help design adaptive management strategies to maintain genetic variation in the context of HIREC.
Technical Report
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Updated tables, figures and references of Palme, 2019, and the respective supplements (Date: 1st July 2022)
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The current study further characterized personality types in Budgerigars, an avian model that only recently demonstrated individual consistencies in behavior (Callicrate et al., 2011). Several methodological techniques, commonly used in previous examinations of other animal models, were employed. Specifically, Phase I assessed the relationship between Budgerigar personality types and Hypothalamic-Pituitary-Adrenal (HPA) activity, while Phase II sought to examine the persistence of individual behavioral tendencies across varying testing contexts. In comparison to other species, our findings failed to illustrate a clear relationship between Budgerigar personality types and concentrations of corticosterone. However, results provided significant evidence for the consistency of personalities across multiple contexts. In sum, our investigation further defined the expression of personality in the Budgerigar and substantiated the claim for individual tendencies in this species.
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The relative contribution of genetic and non-genetic factors in shaping personality traits is of fundamental relevance to biologists and social scientists. Individual animals vary in the way they cope with challenges in their environment, comparable with variation in human personalities. This variation has a substantial genetic basis. Here we describe experiments showing the strength of environmental factors (food availability and sibling competition) in shaping personality traits in a passerine bird (Parus major). We manipulated the early rearing condition in two lines (F4) bidirectionally selected for different personalities (fast line: high exploration speed and high aggression; slow line: low exploration speed and low aggression) with a food rationing protocol inducing an impairment in growth rate and an enhancement in levels of offspring solicitation (begging behaviour). Growth impairment was more marked in the slow line. In a first experiment each nest contained experimental and control siblings of the same line (within-nests design). Slow chicks became much faster than their parents in the exploration tests regardless of the treatment, whereas fast chicks had scores similar to their parents and showed no treatment effect. As a consequence, the line difference in exploration behaviour of the offspring was not apparent in the juvenile phase. Six months later the offspring of the slow line was still relatively fast, but lines differed in exploration, since the fast line became even more fast. Food-rationed birds of the fast line were more aggressive than both controls and their fathers, while treatment did not affect the slow line. In a second experiment, carried out only in the slow line, each nest contained either control or experimental siblings (between-nests design). Now, only the food-rationed chicks became faster in exploration. We suggest that the shift in the controls in the within-nests design was due to enhanced sibling competition, forced by the experimental chick. Indeed, the control chicks in the first experiment begged more persistently and had higher exploration scores than the control chicks in the between-nests design. Environmental factors during ontogeny modulate the expression of phenotypic traits against the background of the reaction norm allowed by the genome even in selected lines of animals resulting in profound and reliable differences in behaviour [KEYWORDS: GREAT TIT ; ONTOGENY ; FOOD AVAILABILITY ; PERSONALITY ; EXPLORATION ; AGGRESSION ; SIBLING COMPETITION]
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Individuals of the same sex or age within a given species often differ from each other in their behaviour and underlying physiology, even under stan-dardized conditions. Most of this variation is non-random and is consistent across situations or contexts and across time. Frequently, these individual dif-ferences become conspicuous and easily measurable when individuals have to cope with everyday challenges in their environment, both social and non-social, as a consequence of the use of different strategies in apparently simi-lar situations (Broom, 2001). Such differences within populations have often been neglected as biologically meaningful variation and interpreted as ei-ther the consequence of inaccurate measurements or non-adaptive variation around an adaptive mean (Wilson, 1998). By contrast, in humans such varia-tion is interpreted as reflecting consistent individual variation in personality or temperament, the science of human personality being already more than one century old. Personality characteristics in humans have a sizeable heri-table component and a proximate basis in genetic polymorphisms and asso-ciated neurobiology, and they have been shown to predict important life out-comes such as health, sexual behaviour and social networks (Nettle, 2005). Recent studies suggest that animal personality can be studied objectively when the concept of personality is translated to an entity that can be quanti-fied with the adequate research tools. A basic definition of personality is that it represents suites of correlated behaviours that are expressed across differ-ent situations. These consistent behavioural features resulting from traits that tend to go together, endow individuals with discernable predispositions. Be-havioural ecologists have long recognised stable inter-individual differences in behaviour or even suites of traits, e.g., the occurrence of different repro-ductive and foraging strategies like 'resident and satellites' or 'producers and scroungers' (Barnard & Sibly, 1981; Clark & Ehlinger, 1987). In the past decade it has become clear that in a wide variety of non-human species (Ta-ble 1) consistent individual differences in one trait covary with other behav- Table 1. Overview of the species in which consistent individual differences in suites of traits (at least two) have been described at different levels of analysis. The list stems from the literature of the articles published in this issue and does not pretend to be exhaustive. ++ means that at least two papers have been published for a given species.
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Repeatability is a useful tool for the population geneticist or genetical ecolo- gist, but several papers have carried errors in its calculation. We outline the correct calcu- lation of repeatability, point out the common mistake, show how the incorrectly calculated value relates to repeatability, and provide a method for checking published values and calculating approximate repeatability values from the F ratio (mean squares among groups/ mean squares within groups).
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A behavioral syndrome is a suite of correlated behaviors expressed either within a given behavioral context (e.g., correlations between foraging behaviors in different habitats) or across different contexts (e.g., correlations among feeding, antipredator mating, aggressive, and dispersal behaviors). For example, some individuals (and genotypes) might be generally more aggressive, more active or bold, while others are generally less aggressive, active or bold. This phenomenon has been studied in detail in humans, some primates, laboratory rodents, and some domesticated animals, but has rarely been studied in other organisms, and rarely examined from an evolutionary or ecological perspective. Here, we present an integrative overview on the potential importance of behavioral syndromes in evolution and ecology. A central idea is that behavioral correlations generate tradeoffs; for example, an aggressive genotype might do well in situations where high aggression is favored, but might be inappropriately aggr
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The plasticity of behaviour consists of an array of behavioural responses to varying environmental conditions. It is widely predicted that the range of behavioural responses will increase with environmental variability. According to this prediction, the slopes of a response curve representing behavioural plasticity would be identical in environments with different variability. However, the range of behaviours can also increase with the slope of the curve, so that in a given range of environments, the plasticity of behaviour would vary. For example, where two environments are similar in terms of resource availability, the costs of exploiting the resource may differ. An improved ability to assess costs and benefits is predicted to increase behavioural plasticity because it decreases the costs and increases the benefits of alternative behaviours. Moreover, because trade-offs change with age and plasticity is related to trade-offs, plasticity should also change with age. While the ability of animals to adjust to current trade-offs is fundamental for behavioural ecology, demonstration of ranges, slopes, and shapes of plastic behavioural responses is virtually absent from the literature. Knowledge concerning the ability of animals to adjust to environmental fluctuations is important for making predictions about population viability, but empirical evidence is greatly needed to validate current generalizations.
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In monogamous animals, reproductive success may vary considerably among pairs. To study this variation, we focussed on reproductive events and the circannual hormonal co-ordination within pairs during the reproductive cycle. Testosterone was chosen as covariable for both sexes because of its mediator function between behaviour and physiology. In a flock of free-living Greylag Geese Anser anser, individual faecal samples were collected weekly from 23 pairs over a complete annual cycle. From the faeces, equivalents of testosterone, oestrogen and other steroid hormones were analysed by enzyme immunoassay. In contrast to correlations between male and female testosterone, no correlations were found between oestrogen-oestrogen or oestrogen-testosterone. Therefore, only testosterone (T) is considered here. Sex-specific differences in T were in amplitude rather than in the annual timing of maxima and minima. However, the annual timing varied to some degree between individuals within sexes. Therefore, we examined the degree of annual testosterone correlation (TC) within pairs. Pairs that nested had significantly higher TC over the year than pairs that did not. The higher the within-pair TC, the larger the clutches and the heavier the eggs. Also, TC in the year investigated was positively and significantly correlated with the pairs' long-term reproductive output. No correlation was found between TC and the duration of the pair-bond, individual age, or age difference from pair partner. We suggest that TC is a measure of behavioural synchrony and, therefore, pair-bond quality. We consider whether within-pair TC results from mate choice.
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Although greylag geese Anser anser establish long-term monogamous pairbonds, some of the existing pairs do split up (divorce) and new pairs are formed during the annual spring mating period. In this study, male greylag geese which were involved in the challenge of an existing pairbond (challenged males and challengers) were regarded as ‘natural experimental’ groups and compared with males in stable pairbonds (unchallenged males and male-paired males, a common male strategy when the availability of females is low). In total, 37 males were investigated. The analysis included a description of the seasonal patterns of hormone levels, aggression and courtship. We tested whether hormone levels correlated with aggressive and courtship behaviours. Finally, we compared hormonal and behavioural patterns amongst the four groups. Immunoreactive testosterone (T) and corticosterone (B) equivalents were measured in faecal samples. Individual hormone levels were correlated with frequencies of agonistic male-male interactions and with frequencies of male-female courtship. During early mating and pre-laying phases, T was at its seasonal maximum, which may have masked hormone-behaviour correlations. During egg-laying, at the onset of seasonally decreased T, agonistic male-male interactions and the frequencies of courtship behaviour were significantly correlated with T. Unchallenged males had higher rates of agonistic interactions than any other males. However, unchallenged and challenged males tended to excrete T at higher levels than challengers. The high rates of being attacked and elevated levels of faecal B were indicative of the social conflict experienced by challengers. No hormonal differences were observed between heterosexually paired males and male-paired males. In summary, pairbond status and situations of social conflict had a modulating effect on T and B; however, in this study, the two hormones seem to be affected independently of one another.
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We investigated the reliability of the non-invasive approach of measuring steroid hormones from feces in the domestic goose (Anser domesticus), a mainly herbivorous bird with a short gut passage time (2–3 h). Groups of eight outdoor-housed male domestic geese were subjected to three different experiments, injection of either GnRH analogue or ACTH, or ”social stimulation” by confrontation with two alien males or females. These experiments were replicated in three different seasons, in spring, during peak reproductive activity, in summer, during long-day photorefractoriness and postnuptial molt, and in fall, during sexual reactivation. GnRH stimulation resulted in significant increases of mean response and peak fecal testosterone metabolites (TM) in spring and fall. Response TM concentrations excreted in spring were generally higher than in summer and fall. Social confrontation with two females, but not with two males, increased mean and peak TM in all seasons. In general, ACTH treatment resulted in a proportionally higher increase of fecal corticosterone metabolites (BM) than GnRH did in fecal TM (80- to 140-fold vs 6- to 8-fold). ACTH significantly increased mean and peak BM in all seasons. Social confrontation with two males significantly increased fecal BM in spring, but confrontation with two females increased fecal BM in fall. Our results indicate that determining steroids from feces is a generally valid approach. However, the sensitivity of the method may vary between different hormones and results may differ between seasons. BM results seemed more sensitive and seasonally robust than did TM.
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Individual differences in temperament may affect how animals react to novel situations, avoid predation, invest in reproduction and behave in a variety of social contexts. Little information is available, however, about individual differences in temperament for wild animals. For bighorn sheep, Ovis canadensis, ewes captured as part of a long-term study, we compared behaviour during handling to behaviour in the field and reproductive history. We considered ‘bold’ ewes those that were frequently trapped during the summer, and assigned to each ewe a docility index based on her behaviour during handling. Measurements of temperament for the same individual at different captures were highly consistent. Temperament was not affected by reproductive status or age, nor was it related to body mass. Correlations between behaviour at the trap and in the field were weak and mostly nonsignificant, suggesting that temperament is domain specific rather than domain general. Bold ewes tended to start reproducing earlier and have higher weaning success than shy ewes. Variability in temperamental traits in the study population could be maintained by life-history trade-offs and by yearly changes in selective pressures.
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Seasonal patterns of fecal 17β-OH-androgen, estrogen, and progesterone equivalents of male and female greylag geese (Anser anser) were analyzed in a flock of free-living geese. These were compared among social categories determined by pairbond status and breeding success. The annual cycle was divided into 13 phases. Phasewise intra-sexual comparisons were made between social categories. The seasonal variation obtained from feces was in general agreement with the literature on plasma patterns in geese and other temperate-zone birds. However, there were distinct differences in seasonal hormone patterns among the social categories. In unpaired males, androgen was elevated for a longer period of time during sexually active phases compared with paired males. In male geese, high levels of androgen did not interfere with parenting but were related to pairbond status, whereas in females, androgen and progesterone were positively related to parental behavior. In the Fall, androgen, progesterone, and estrogen peaked only in unpaired males. In unsuccessful females, estrogen started to increase earlier in the Winter and was higher in amplitude and duration than that in females guarding offspring. In general, fecal steroids showed a clear-cut difference only between sexually active and parental phases of the year in the successfully breeding pairs, whereas unpaired males retained a hormonal state closer to sexually active phases throughout the year.
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The evolutionary continuity between humans and other animals suggests that some dimensions of personality may be common across a wide range of species. Unfortunately, there is no unified body of research on animal personality; studies are dispersed across multiple disciplines and diverse journals. To review 19 studies of personality factors in 12 nonhuman species, we used the human Five-Factor Model plus Dominance and Activity as a preliminary framework. Extraversion, Neuroticism, and Agreeableness showed the strongest cross-species generality, followed by Openness; a separate Conscientiousness dimension appeared only in chimpanzees, humans' closest relatives. Cross-species evidence was modest for a separate Dominance dimension but scant for Activity. The comparative approach taken here offers a fresh perspective on human personality and should facilitate hypothesis-driven research on the social and biological bases of personality.
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Individual differences in personality affect behavior in novel or challenging situations. Personality traits may be subject to selection because they affect the ability to dominate others. We investigated whether dominance rank at feeding tables in winter correlated with a heritable personality trait (as measured by exploratory behavior in a novel environment) in a natural population of great tits, Parus major. We provided clumped resources at feeding tables and calculated linear dominance hierarchies on the basis of observations between dyads of color-ringed individuals, and we used an experimental procedure to measure individual exploratory behavior of these birds. We show that fast-exploring territorial males had higher dominance ranks than did slow-exploring territorial males in two out of three samples, and that dominance related negatively to the distance between the site of observation and the territory. In contrast, fast-exploring nonterritorial juveniles had lower dominance ranks than did slow-exploring nonterritorial juveniles, implying that the relation between dominance and personality is context-dependent in the wild. We discuss how these patterns in dominance can explain earlier reported effects of avian personality on natal dispersal and fitness. Copyright 2004.
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Preface 1. Temperament and personality: trait structure and persistence 2. Psychobiological methods 3. Extraversion/sociability 4. Neuroticism 5. Psychoticism (psychopathy), impulsivity, sensation and/or novelty seeking, conscientiousness 6. Aggression-hostility/agreeableness 7. Consilience References.
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The behaviour of house cats Felis silvestris catus from nine litters was recorded at 4 months, 1 year and 2 years of age, in their home environment immediately after meals fed by their owners. We extracted by principal components analysis four elements of 'behavioural style' that were consistent from one age to another: based upon behaviour patterns that were most heavily loaded on each component, these were labelled as Staying Indoors, Rubbing, Investigative and Boldness elements. The Staying Indoors and Rubbing elements are similar to two aspects of behavioural style identified in a previous study of adult cats; the Boldness element, possibly coupled with the Investigative element, may be similar to the shy/bold continuum identified in controlled studies of cats and other species. Four-month-old male cats were the most likely to Stay Indoors; the Rubbing element increased with age in the majority of individuals, both male and female. Littermates tended to be similar to one another in Rubbing (at 4 months) and Boldness (up to 1 year). A positive effect of handling received during the first 8 weeks of life was detected for Boldness at 4 months of age.
Article
Amid the deleterious consequences of prolonged stress, there is tremendous variability in how readily various stressors provoke stress responses in different individuals. This review covers some of the underpinnings of such differences, heavily emphasizing adrenocortical secretion of glucocorticoids during stress, and responsiveness to psychological, rather than physical stressors. Psychological stress is shown to involve loss of control or of predictability, an absence of outlets for frustration, an absence of social support, and a perception of events worsening; some powerful studies show that the physiological and pathophysiological responses to identical physical stressors will vary dramatically as a result of manipulating some of those psychological variables. Those findings are then used to interpret a literature concerning differences in the stress response among individuals of different ranks among a variety of social animal species. In a broad manner, social dominance in a stable hierarchy, with its attendant psychological rewards, is associated with a more adaptive stress response, as measured by a number of physiological endpoints. However, considerable subtleties in this relationship exist, transcending the mere issue of rank. Instead, rank and its physiological correlates are sensitive to the society in which the rank occurs, the individual's experience of both that rank and that society, and personality factors that color the perception of external events. Finally, these primate studies are used to interpret data in the health psychology field concerning individual differences and coping mechanisms in humans.
Article
The evolutionary continuity between humans and other animals suggests that some dimensions of personality may be common across a wide range of species. Unfortunately, there is no unified body of research on animal personality; studies are dispersed across multiple disciplines and diverse journals. To review 19 studies of personality factors in 12 nonhuman species, we used the human Five-Factor Model plus Dominance and Activity as a preliminary framework. Extraversion, Neuroticism, and Agreeableness showed the strongest cross-species generality, followed by Openness; a separate Conscientiousness dimension appeared only in chimpanzees, humans' closest relatives. Cross-species evidence was modest for a separate Dominance dimension but scant for Activity. The comparative approach taken here offers a fresh perspective on human personality and should facilitate hypothesis-driven research on the social and biological bases of personality.
Article
Adult males from one line (Short Attack Latency = SAL line) are more aggressive, show less sensitivity to changes in their environment and behave in a more internally controlled, routine-like way, than do males from the other line (outbred=Control line). Paternal care did not differ between the two lines, but SAL pups received higher levels of nursing and general maternal care than did Control pups, and they appeared to be weaned later. Despite these differences, SAL pups grew more slowly, suggesting that their high levels of sucking behaviour were a reflection of high milk demand, perhaps due to a low milk supply, rather than high milk intake. From day 32 onwards, SAL pups began to show higher levels of aggression towards each other than did Control pups. SAL males developed into faster attackers than Control males and, in SAL litters, intra-litter variation in attack speed was strongly influenced by preceding experience of sibling aggression. Inadequate nutrition of young SAL pups, mediated through the mother may promote increased competition for access to the mother's nipples and predispose pups to develop into more active/competitive individuals. (See also 92L/07305). -from Authors
Article
To investigate the relationship between aggression and routine-like behaviour the response of male mice of bidirectionally selected lines for attack latency to a change in the social and non-social environment has been measured. In a non-social situation the extent of routine-like behaviour was measured in a Y-maze in which only one of the two arms gave access to the food compartments. The number of errors made in response to reversal of the arm that was blocked was taken as indicator for the degree of routine formation. Males of the short attack latency (SAL) line made significantly more errors, and hence were more routine-like in their performance, than mice of the long attack latency (LAL) line. Males of the LAL line that nevertheless had short attack latencies (i. e. aggressive LAL mice) turned out to be flexible in their behaviour; their response was similar to that of the non-aggressive LAL males. In a social situation SAL and aggressive LAL mice were used to investigate routine formation in attacking behaviour. The males were given different amounts of experience with male opponents after which their own female was introduced as opponent. The more extended the experience with male intruders was, the more SAL males subsequently attacked their female. In contrast, LAL mice appropriately changed their behaviour towards the female opponent. Thus, the attacking behaviour of SAL mice gets routine-like, whereas that of LAL males remains flexible. It is concluded that selection for attack latency generally coincides with selection for routine-like behaviour, suggesting that these two factors are influenced by many of the same genes. Regarding the fact that aggressive males of the LAL line show flexible behaviour, it may be proposed that with the phenotypic selection for attack latency there has in fact been selected for a mechanism that determines the organization (routine-like vs flexible) of behaviour.
Article
In mammals, support by a social partner may reduce stress levels and ease access to resources. We investigated the effects of the passive presence of a nearby social ally on excreted corticosterone immunoreactive metabolites and behaviour in juvenile graylag geese (Anser anser). Two groups of hand-raised juveniles (N1 = 9, N2 = 3) were tested over 1 year by positioning humans of different familiarity (i.e., the human foster parent, a familiar human, a nonfamiliar human, no human) at a standard distance to the focal geese. Their success in agonistic interactions significantly decreased with age and with decreasing familiarity of the accompanying human. The humans present modulated the excretion of corticosterone immunoreactive metabolites, with the strongest effects recorded after fledging when corticosterone metabolites were also positively correlated with agonistic behaviour. This suggests that a human foster parent may provide similar supportive benefits as goose parents do in natural families. We discuss the benefits of social alliances with regard to the integration into the flock, access to resources, and life history.
Article
To search for a pattern of behaviour similar to the one found for active and passive coping strategies in rodents, we tested piglets in a series of different tests. One of the tests was a restraint test previously used by Hessing et al. (1993a,b). In this test the piglet was turned on its back and held there for 1 min while the number of escape attempts was counted. This first test was done on 65 piglets (males and females, 2 weeks of age). In our study the result of the back-test was unimodal, not bimodal as suggested by Hessing et al. (1993a,b). The back-test was then repeated over time on another group of piglets (once a week; all piglets female, n = 45, 1–5 weeks old). In addition, a number of other tests were done (8–10 weeks). These were tests designed to measure parameters that previous studies have shown to be correlated to the coping strategies of the animals: namely, extinction time, social dependence, reaction to a novel object, and aggression in an owner/intruder conflict. We did not find any correlation between the latency to attack and the parameters measured and thus found no evidence for the existence of active/passive copers in domestic pigs. A principal component analysis (that explained 60% of the total variation) suggested three personality traits: aggression (25%), sociability (20%) and exploration (15%).
Article
During the last decades more and more attention has been focused on the function of the stress hormone corticosterone in free-living birds. Normally birds have low circulating levels of corticosterone throughout the year, but when exposed to a stressor they will, however, rapidly increase the corticosterone secretion, and thereby adjust their phyiology and behaviour to the new situation. To avoid chronic effects of high corticosterone levels the secretion rate returns to basal as soon as the alternate behaviour has been established or when the individual in some other way has succeeded to cope with the stressor. In short, elevated corticosterone levels will redirect behaviour away from reproduction towards survival, for example by stimulating dispersal and/or foraging behaviour. However, a bird must be able to modulate the adrenocortical stress response as one and the same response will have different biological effects in different ecological situations. So that at a certain time the bird should react rapidly to a stressor, whereas in another situation it should have a suppressed response to the same stressor. Thus, it is the adrenocortical stress response at a particular time, and not the basal corticosterone level, that affects an individuals' fitness and consequently the target for evolutionary forces. This paper reviews studies dealing with the adrenocortical stress response in birds. A major hypothesis is that seasonal modulations of an acute stress response should be found basically in species with short breeding seasons and/or in species breeding in severe environments. Although the patterns differ between species, most studies support this hypothesis. As a stress induced elevation of corticosterone levels can disrupt reproductive functions and reduce reproductive succees birds not only modulate their adrenocortical stress response on a seasonal basis, but also within or between populations. Among populations in, a species breeding in a wide variety of habitats those breeding in a more unpredictable and severe habitat normally are less sensitive to environmental Stressors. Consequently individuals in such a population have a suppressed adrenocortical stress response to an acute stressor. There are, however, some interesting exceptions to this rule. The selective forces behind these differences are so far unknown. In addition there are normally large inter-individual variations, as well as sex related differences, in the adrenocortical stress response. It has been suggested that individuals with large fat depots should be the ones to be more resistent to acute stress as they are less likely to be affected by, for example, severe weather conditions. Furthermore, it has been hypothesised that the sex investing most in parental responsibilities should reduce the adrenocortical stress response to avoid in duction of a corticosterone mediated escape behaviour. Results from different studies are however not always consistent with these hypotheses, and the bases for individual variations are today unclear. The adrenocortical stress response is also discussed in relation to social hierarchies and migratory strategies.
Article
The person-situation debate is coming to an end because both sides of the debate have turned out to be right. With respect to momentary behaviors, the situation side is right: Traits do not predict, describe, or influence behavior very strongly; the typical individual's behavior is highly variable; and a process approach is needed to explain that variability. With respect to trends (e.g., a person's typical way of acting), however, the person side of the debate is right: Traits predict and describe behavior very well over long stretches of time, behavior is highly stable, and a trait approach is needed to explain differences between people. Thus, proponents of both sides are right and should continue to conduct fruitful research, and both viewpoints are necessary for a full understanding of personality. The next exciting steps in personality psychology will include integrating these two approaches in the same research paradigm.
Article
Families proved dominant over pairs, pairs over unpaired birds, and single males dominated single females. Single females with young ranked between families and pairs, and lone breeding males whose females were incubating ranked between pairs and unpaired individuals. The dominance value of pairs in winter correlated with subsequent fledging success, and there was some evidence that high-ranking males are more likely to obtain a mate. A positive feedback system 'age rt arrow dominance rt arrow fledging success rt arrow high dominance rt arrow fledging success' is suggested which could account for the 'delayed breeding' common in geese and swans. In pairs or families male age correlated more strongly than female age with winter dominance. Presence of the mate and/or offspring increases fighting motivation, thus explaining the dependence of rank on the social context. The hierarchy of social classes can be explained by geese signalling their degree of fighting motivation to each other. -from Author
Article
The concepts of alternative strategy and coping strategy and their relevance to applied studies of social behaviour are considered. It is clear that a universally agreed definition of “strategy” is not available, and that there are few good examples of discrete social strategies in applied ethology. However, general principles emerging from theoretical and empirical studies of behavioural strategies do have some value for applied ethology research. Alternative strategy theory emphasises the importance of measuring the costs and benefits of different types of social behaviour, and of being aware that different behavioural solutions to the same problem may be equally successful. There are significant problems in using a cost/benefit currency of inclusive fitness in applied studies of domestic animals, but a currency related to measures of animal welfare may be of use and of relevance to applied ethologists. Cost/benefit analysis may reveal that the “traditional” view of a positive linear relationship between social rank and measures of welfare or fitness is not always correct. In some cases, animals of quite different social rank may do similarly well in terms of their welfare and reproduction. The idea that individuals respond to threatening or challenging situations using specific coping strategies may have some applicability in social contexts. During introduction to novel conspecifics, or social upheaval, individuals may behave in ways in which are reasonably predictable from a knowledge of their coping strategies. However, it is argued that such predictability is unlikely in stable social groupings and thus has limited practical value. Nevertheless, this remains to be investigated experimentally. If consistent coping strategies in social situations are found to exist, it is possible that they may represent frequency-dependent alternative strategies whose costs and benefits can be analysed. If so, there will be a population equilibrium point at which followers of different strategies are, on average, equally successful. From a practical perspective, it is possible that this population structure also results in minimal welfare problems and maximal growth rates.
Article
Consistent individual variation in behaviour, creating within-species categories of individuals, is predicted from game theory and has been observed in studies of coping