An animal’s social environment can be both dynamic and complex. Thus, social species often garner fitness benefits through being plastic in their social behavior. Yet, social plasticity can be constrained by an individual’s experience. We examined the influence of early social environment on social behavior in the tree skink (Egernia striolata), a family-living lizard. In the first phase of this study, we reared juveniles in 2 different social environments for 1.5 years: either in isolation or in unrelated pairs. We quantified each lizard’s sociability at 4-month intervals using a standardized laboratory assay and found that isolated lizards were more sociable, spending the assay closer to an adult female, than socially-reared lizards. In the second phase of this study (at the end of 1.5 years), we released all lizards into a semi-natural environment, observed their associations, and used social network analysis to quantify social behavior. During the initial 6 weeks post-release, we detected no differences in social behavior between rearing treatments. However, during the following 6 months differences emerged. Isolated lizards were more homogeneous in the strength of their associations than socially-reared lizards. Also, at first, isolated lizards associated more strongly than socially-reared lizards. Over time, isolated lizard associations became weaker and involved fewer lizards. In contrast, the level and number of associations of socially-reared lizards were stable over time. Our findings suggest that early experience influences tree skink social behavior but does not constrain social plasticity: isolation rearing did not limit their ability to respond to a novel social environment.
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... Stable environments can generate stable personalities (Roberts and Caspi 2003), whereas changes to the environment can encourage personality change (Ardelt 2000). In non-human animals, accumulating evidence suggests that changes to the social environment encourage behavioral plasticity (Riley et al. 2018;Munson et al. 2021;Skinner and Miller 2022), whereas animals in consistent social environments demonstrate fairly consistent social behavior (Jacoby et al. 2014;Skinner and Miller 2022). ...
... Research on tree skinks (Egernia striolata) has demonstrated that social isolation at an early age increases sociability. However, when pair-housed and isolated individuals were later housed together as adults, formerly isolated lizards adapted their social behavior to reflect their new social environment (Riley et al. 2018). The social plasticity demonstrated by tree skinks may be the result of a non-obligatory social system, in which social isolation is a natural part of development (Riley et al. 2018). ...
... However, when pair-housed and isolated individuals were later housed together as adults, formerly isolated lizards adapted their social behavior to reflect their new social environment (Riley et al. 2018). The social plasticity demonstrated by tree skinks may be the result of a non-obligatory social system, in which social isolation is a natural part of development (Riley et al. 2018). In northern climates, gartersnakes must aggregate with conspecifics for hibernation and mating (Rossman et al. 1996). ...
Personality traits are consistent across time and context, by definition, but the expression of personality in behavior is affected by both developmental and environmental factors. Little is known about the long-term effects such factors have on stability and change in personality traits, especially in understudied species. Research on species with different ecologies than more commonly studied mammals and birds can provide valuable insight into environmental influences on the stability of personality. We performed two experiments to investigate boldness and sociability in Eastern gartersnakes (Thamnophis sirtalis) in the laboratory. We first examined the developmental trajectories of these personality traits across the first 8 months of snakes’ lives. Next, we tested whether one month of social isolation could drive changes in either trait. Boldness and sociability displayed two different patterns of consistency and change. Across early development, gartersnakes display a shy–social correlation and are consistent in their boldness but not their sociability. Social isolation in contrast leads to changes in boldness for some snakes, while sociability remains consistent. These patterns of change are moderated by both sex and weight and may serve to drive male-biased dispersal of larger snakes early in life, and their re-settlement later on. In females, trait flexibility may help to balance the benefits of socializing while minimizing competition over food. These results highlight how the dynamics of personality development and stability may vary across taxa, driven by differences in ecology.
Significance statement
How personality traits are expressed in response to developmental changes and environmental pressures is an active area of research. Many studies of personality in non-human animals look for consistency in personality across short periods of time, and in response to moderate environmental change—methods that may miss important developmental changes. Here, we tested for changes in gartersnake personality during the first 8 months of development—an important time period for dispersal and resettlement, and in response to a change in their social environment. We found evidence that the expression of personality is trait-specific. For gartersnakes, boldness is consistent across time but changes in response to the social environment, whereas sociability displays the opposite pattern. These patterns of personality expression are different from more typically studied laboratory animals and emphasize the importance of studying species that experience a variety of selective pressures and social environments.
... For example, delicate skinks (Lampropholis delicata) show repeatability in boldness within non-social and social contexts, but not when boldness is compared across these two contexts (Brand et al. 2022). In addition, tree skinks (Egernia striolata) that were reared in isolation demonstrated plasticity in their sociability across social contexts (Riley et al. 2018). ...
... Such situational plasticity has been termed 'social competency', as it represents alteration of typical behavior heuristics to the demands of the social context (Duboscq et al. 2016;Taborsky and Oliveira 2012). Social-cognitive perspectives on personality are rare in reptile literature, but offer valuable insight into shared processes across social systems (e.g., Riley et al. 2018). In addition to such situational conformity, individual differences in flexibility influenced behavioral plasticity. ...
Personality traits drive individual differences in behaviour that are consistent across time and context. Personality limits behavioural plasticity, which could lead to maladaptive choices if animals cannot adapt their behavior to changing conditions. Here, we assessed consistency and flexibility in one personality trait, boldness, across non-social and social contexts in eastern gartersnakes (Thamnophis sirtalis sirtalis). Snakes explored a novel open arena either alone or in a pair. Pairs were assigned based on the data from the solo trials, such that each snake was paired once with a bolder and once with a less bold partner. We predicted that snakes would conform when in a social context, displaying plasticity in their personality, and causing boldness scores to converge. We found that snakes were consistent within contexts (solo or paired), but changed their behavior across contexts (from solo to paired). Plasticity in boldness resulted from an interaction between conformity and repeatable individual differences in plasticity. In line with some data on other species, snakes conformed more when they were the less bold partner. Personality reflects a consistent bias in decision-making, but our results highlight that the cognitive processes that drive the expression of personality traits in behavior are flexible and sensitive to social context. We show that both consistency and plasticity combine to shape snake social behavior in ways that are responsive to competition. This pattern of behavior may be particularly beneficial for species in which group-living is seasonal.
... High CV values suggests that the focal skink's associations are variable; in contrast, low CV values means that focal skink's associations with conspecifics are relatively homogeneous (Riley et al., 2018b). We used three separate linear models to test if these network metrics differed between adult female, adult male, and juvenile skinks (details in Supplementary Materials). ...
... First, how does variation in individual social behavior link to fitness? Previous work has shown, within an experimental context, that Tree Skinks can be plastic in their social associations, potentially maximizing individual benefits within a dynamically changing environment (Riley et al., 2018b). In the field, Bonnett (1999) found that individual vigilance rates (head movements per minute) were lower for grouped sub-adults than lone sub-adults, but this trend was not observed in adults. ...
There is great diversity in social behavior across the animal kingdom. Understanding the factors responsible for this diversity can help inform theory about how sociality evolves and is maintained. The Australian Tree Skink (Egernia striolata) exhibits inter- and intra-population variability in sociality and is therefore a good system for informing models of social evolution. Here, we conducted a multi-year study of a Tree Skink population to describe intra-population variation in the social organization and mating system of this species. Skinks aggregated in small groups of 2–5 individuals, and these aggregations were typically associated with shared shelter sites (crevices and hollows within rocks and trees). Aggregations were typically made up of one or more adult females and, often, one male and/or juvenile(s). Social network and spatial overlap analyses showed that social associations were strongly biased toward kin. Tree skinks also exhibited high site fidelity regardless of age or sex. There were high levels of genetic monogamy observed with most females (87%) and males (68%) only breeding with a single partner. Our results indicate that Tree Skinks reside in small family groups and are monogamous, which corresponds with existing research across populations. Similar to previous work, our study area consisted of discrete habitat patches (i.e., rock outcrops, trees, or both), which likely limits offspring dispersal and promotes social tolerance between parents and their offspring. Our study clearly demonstrates that there is intra-population variability in Tree Skink social behavior, but it also provides evidence that there is a high degree of inter-population consistency in sociality across their geographic range. We also highlight promising possible avenues for future research, specifically discussing the importance of studying the nature and extent of Tree Skink parental care and quantifying the fitness outcomes of kin-based sociality in this species, which are topics that will further our understanding of the mechanisms underlying variation in vertebrate social behavior.
... Andersen, 2003;Bateson, 1979;Carere & Maestripieri, 2013;Fawcett & Frankenhuis, 2015;MacDonald, 1985). The few studies addressing the influence of early social isolation on animal personality traits are difficult to interpret because of social contact among siblings occurring before birth, hatching or emergence, such as within the placenta (Riley et al., 2018 for skinks) or egg sac (Liedtke et al., 2015 for jumping spiders). This can potentially obscure or change subsequent social isolation effects. ...
Animal personalities are characterized by intra‐individual consistency and consistent inter‐individual variability in behaviour across time and contexts. Personalities abound in animals, ranging from sea anemones to insects, arachnids, birds, fish and primates, yet the pathways mediating personality formation and expression remain elusive.
Social conditions during the early postnatal period are known determinants of mean behavioural trait expressions later in life, but their relevance in shaping personality trajectories is unknown.
Here, we investigated the consequences of early social isolation on adult personality expression in plant‐inhabiting predatory mites Phytoseiulus persimilis. These mites are adapted to live in groups. We hypothesized that transient experience of social isolation early in life, that is, deprivation of any social contact during a sensitive window in the post‐hatching phase, has enduring adverse effects on adult personality expression.
Newly hatched mites were transiently reared in isolation or in groups and tested as adults for repeatability of various within‐group behaviours, such as movement patterns and mutual interactions including sociability, defined as the propensity to associate and interact benignly with conspecifics, and activity patterns when alone. Groups composed of individuals with the same or different early‐life experiences were repeatedly videotaped and individual behaviours were automatically analysed using AnimalTA.
Social experiences early in life had persistent effects on mean behavioural traits as well as adult personality expression, as measured by intraclass correlation coefficients (indicating repeatability). On average, isolation‐reared females moved at higher speeds, meandered less, kept greater distances from others and had fewer immediate neighbours than group‐reared females. Group‐reared females were highly repeatable in inter‐individual distance, moving speed, meandering and area explored, whereas isolation‐reared females were repeatable only in the number of immediate neighbours. Activity, quantified as the proportion of time spent moving within groups, was only repeatable in group‐reared females, whereas activity, quantified as the proportion of time spent moving when alone, was only repeatable in females reared in isolation. Strikingly, also the early‐life experiences of male mates influenced personality expression of mated females, with isolation‐reared males boosting the repeatability of behavioural traits of group‐reared females.
Overall, our study provides evidence that a transient phase of social isolation during a critical period early in life has lasting effects that extend into adulthood, impairing adult personality expression. These effects should cascade upward, changing the phenotypic composition and diversity within populations.
... Andersen, 2003;Bateson, 1979;Carere & Maestripieri, 2013;Fawcett & Frankenhuis, 2015;MacDonald, 1985). The few studies addressing the influence of early social isolation on animal personality traits are difficult to interpret because of social contact among siblings occurring before birth, hatching or emergence, such as within the placenta (Riley et al., 2018 for skinks) or egg sac (Liedtke et al., 2015 for jumping spiders). This can potentially obscure or change subsequent social isolation effects. ...
Animal personalities are defined as within-individual consistency and consistent inter-individual variability in behavior across time and contexts. Personalities are observed across animals, ranging from sea anemones to insects, arachnids, birds, fish, and primates, yet the pathways mediating personality formation remain elusive. Genetic predisposition, personal experience and transgenerational information transfer play critical roles. Social conditions during the early postnatal period are known determinants of mean behavioral trait expressions later in life but their relevance in shaping personality trajectories has rarely been examined. Here, we investigated the consequences of early-life social isolation on adult personality expression in plant-inhabiting predatory mites Phytoseiulus persimilis. These predatory mites are adapted to live in groups, primarily because they forage exclusively on patchily-distributed spider mites. We hypothesized that transient experience of social isolation early in life, i.e. deprivation of any social contact during a sensitive window in the early post-hatching period, has enduring adverse effects on social competence and personality expression as adults. Freshly hatched mites were transiently reared in isolation or in groups and tested as adults for repeatability of various within-group behaviors including sociability, defined as the propensity to associate and interact benignly with conspecifics, and activity patterns when alone. Groups composed of individuals with the same or different early-life experiences were videotaped and individual behaviors were automatically analyzed using AnimalTA. Social experiences early in life had persistent effects on mean behavioral traits as well as personality expression as adults, as measured by intraclass correlation coefficients (ICC; indicating repeatability). On average, isolation-reared females moved at higher speeds, meandered less, kept greater distances from others and had fewer immediate neighbors than group-reared females. Group-reared females were highly repeatable in inter-individual distance, moving speed, meandering, distance traveled and exploration, whereas isolation-reared females were repeatable only in number of immediate neighbors. Activity, quantified as the proportion of time spent moving within groups, was only repeatable in group-reared females, whereas activity, quantified as the proportion of time spent moving when alone, was only repeatable in females reared in isolation. Strikingly, also the early-life experiences of male mates influenced personality expression of mated females, with isolation-reared males boosting the repeatability of behavioral traits of group-reared females. Overall, our study provides evidence that a transient phase of social isolation during a critical period early in life has lasting effects that extend into adulthood, impairing social competence and personality expression.
... However, the traits and environmental factors that determine an individual's position in a social network remain poorly understood. There are currently only a small handful of studies assessing the relationship between social experience and future network position (McDonald 2007;Crailsheim et al. 2020;Kurvers et al. 2020), and even fewer that experimentally manipulate experience to explicitly test its effects on various network metrics (Riley et al. 2018;Brandl et al. 2019;Bentzur et al. 2021). To address these gaps, we examined how prior experience with conspecifics influences the strength of individuals' opposite-sex associations. ...
Living in groups can provide essential experience that improves sexual performance and reproductive success. While the effects of social experience have drawn considerable scientific interest, commonly used behavioural assays often do not capture the dynamic nature of interactions within a social group. Here, we conducted three experiments using a social network framework to test whether social experience during early adulthood improves the sexual competence of bed bugs (Cimex lectularius) when placed in a complex and competitive group environment. In each experiment, we observed replicate groups of bed bugs comprising previously socialized and previously isolated individuals of the same sex, along with an equal number of standardized individuals of the opposite sex. Regardless of whether we controlled for their insemination history, previously isolated males mounted and inseminated females at significantly higher rates than previously socialized males. However, we found no evidence of social experience influencing our other measures of sexual competence: proportion of mounts directed at females, ability to overcome female resistance, and strength of opposite-sex social associations. We similarly did not detect effects of social experience on our female sexual competence metrics: propensity to avoid mounts, rate of successfully avoiding mounts, opposite-sex social association strength, and rate of receiving inseminations. Our findings indicate that early social experience does not improve sexual competence in male and female bed bugs.
... In December 2013, we collected 27 gravid, female E. striolata by hand, lasso, or Elliot trap near Albury, NSW, Australia (35.98"S, 146.97"E) for a series of experimental studies investigating the effect of social environment on behavioral development (Riley et al., 2016;Riley et al., 2017, Riley et al., 2018a, Riley et al., 2018b. After capture, we uniquely marked each individual with a Passive Integrated Transponder (PIT) tag and took a tissue sample (removing less than 0.5 cm of the tip of the tail with scissors). ...
The ability to produce viable offspring without recently mating, either through sperm storage or parthenogenesis, can provide fitness advantages under a suite of challenging ecological scenarios. Using genetic analysis, we demonstrate that three wild-caught female Tree Skinks (Egernia striolata) reproduced in captivity with no access to males for over a year, and that this is best explained by sperm storage. To the best of our knowledge, this is the first time female sperm storage has been documented in any monogamous family-living reptile, including social Australian egerniine skinks (from the subfamily Egerniinae). Furthermore, by using paternal reconstruction of genotypes we show that captive-born offspring produced by the same females in the preceding year, presumably without sperm storage, were sired by different males. We qualitatively compared aspects of these females’ mates and offspring between years. The parents of each litter were unrelated, but paternal and offspring genotypes from litters resulting from stored sperm were more heterozygous than those inferred to be from recent matings. Family-living egerniine skinks generally have low rates of multiple paternity, yet our study suggests that female sperm storage, potentially from outside social partners, offers the real possibility of benefits. Possible benefits include increasing genetic compatibility of mates and avoiding inbreeding depression via cryptic female choice. Sperm storage in Tree Skinks, a family-living lizard with a monogamous mating system, suggests that females may bet-hedge through extra-pair copulation with more heterozygous males, reinforcing the idea that females could have more control on reproductive outcomes than previously thought.
It has been suggested that social behavior in squamates evolved partly due to increased interaction opportunities at communal dens and/or due to vivipary. Ball pythons are not viviparous, are not known to communally den, and are often assumed to be non-social. However, as ball pythons are highly cryptic, little is actually known about their social behavior. Here, we examine social interactions and their relationship to personality in juvenile ball pythons (Python regius; n = 30) and find evidence, contrary to expectations, that they are highly gregarious. We tested snakes in both an aggregation assay and in individual personality tests. For the aggregation assay, 5 separate mixed-sex groups of 6 snakes were tracked in a large arena for 10 days. For the personality tests, we tested snakes alone for boldness and sociability. We assessed the snakes’ social interaction patterns within and between the group and individual assays. We found that ball pythons spent much of their time in one large aggregate and used a home base to facilitate social interaction. The snakes were less consistent in their behavior during individual testing, resulting in flexible, rather than consistent, behavior across contexts. Social complexity is thought to determine the number and nature of social interactions between conspecifics, which often results in only testing species that exhibit highly visible social behaviors. Our findings demonstrate that such biased sampling, which often ignores cryptic behavior, provides an incomplete picture of the biological and ecological factors that influence social behavior.
Developmental studies of sociality in non-human animals can offer important insights into the evolution, function, and plasticity of social behavior, especially in understudied species. We examined the development of social behavior in gartersnakes. We hypothesized that social interactions change as snakes age, but are relatively stable in the short term. To assess developmental changes in social patterns, we examined the social tendencies of a group of 6 eastern gartersnakes over the first year and a half of their lives. We placed the snakes in an arena for 8 days and recorded the time that they spent in physical proximity to each other. We repeated this 8-day process 7 times across the snakes’ development. We looked at changes in association patterns and individual differences in sociality (i.e., network position), and examined the effect of group size reduction on social behavior. We found that individuals tended to show repeatable network position across time, but there was a behavioral divide between younger snakes and mature snakes. When male snakes reached sexual maturity, they began initiating most social interactions. Additionally, group member attrition caused the networks to tighten, and the population reduction in combination with sexual maturity created stable social networks. This research shows that social context can have important effects on sociability, and that even a species without permanent social groups will be influenced by its social environment.
The social niche hypothesis theorizes that repeated social interactions between group members is an important mechanism for generating consistent individual differences in behaviour. However, such frequent interactions also have the potential to mask or suppress behavioural differences if individuals conform towards a group behavioural norm (i.e. the social conformity hypothesis) by either synchronizing their behaviour or shifting their behaviour towards that of influential group members. Both of these predictions hinge on the notion that social feedback among group members plays a key role in modulating consistent behavioural variation; thus, in the absence of such feedback, it could be expected that such consistent variation will be reduced. Here, we investigated how a 1-month housing with a stable social group, as opposed to being socially isolated, affected consistent individual differences in the shoaling tendencies of threespine stickleback, Gasterosteus aceluteus. Specifically, we repeatedly tested the tendency of individual sticklebacks to shoal with conspecifics before and after their social experience. In support of the social conformity hypothesis, we observed a four-fold increase in among-group differences, but no change in among-individual differences, in the shoaling tendencies of sticklebacks housed in groups. A post hoc analysis revealed that the increase in among-group differences may have been driven by the most ‘social’ pretreatment group member. Conversely, fish that were housed in isolation, expressed a notable, albeit nonsignificant, decrease in individual shoaling variation and repeatability. This decrease in shoaling variation corresponded with an increase in the average shoaling tendencies of solitary fish post-treatment, suggesting that solitary fish converged towards a similarly high level of shoaling tendencies post-treatment. For both treatment groups, however, we found among-individual positive correlations in pre- and post-treatment shoaling tendencies, suggesting that individuals may inherently differ in their shoaling tendencies, but that the social environment plays an important role in mediating the expression of these differences.
The social environment during development can affect learning; for example, raising an obligate social mammal in isolation can hinder their learning ability. However, we know little about how the social environment impacts learning in less-studied, facultatively social taxa, like family-living lizards. We reared tree skinks (Egernia striolata) in two treatments, either with a conspecific or in isolation. We used three tasks to quantify skink learning ability (motor, discrimination, and reversal). Skinks performed these tasks under two learning treatments: either after demonstration (social learning) or without social information (individual learning). We did not find any evidence that tree skinks used social information. The majority of skinks learnt our motor (91%) and discrimination tasks (100%), and a third learnt our reversal task (34%). Contrary to our predictions, and the majority of previous literature, we detected no negative effect of rearing treatment on learning in any task. Our surprising findings are likely due to this skink’s variable social system, and we suggest that birds and mammals with facultative sociality may not be affected by isolation rearing in the same way as taxa with obligate sociality.
Significance statement
Survival can be impacted by an animal’s ability to learn, but many factors can influence this ability (i.e., age, sex, stress, and developmental environment). In this study, we examined how social environment across ontogeny impacts the learning ability of a facultatively family-living animal, the tree skink. Traditionally, the relationship between social environment and learning has been examined in obligate social species. But, examining this relationship in species across all social systems aids in our understanding of the evolution of sociality, and the consequences and limitations of each social system. We found the social environment tree skinks were raised in did not affect their social or individual learning abilities across three foraging tasks. Our findings provide an initial examination of how social environment impacts learning in a facultatively social species.
There is a long-standing debate as to whether social or physical environmental aspects drive the evolution and development of cognitive abilities. Surprisingly few studies make use of developmental plasticity to compare the effects of these two domains during development on behaviour later in life. Here, we present rearing effects on the development of learning abilities and social behaviour in the jumping spider Marpissa muscosa. These spiders are ideally suited for this purpose because they possess the ability to learn and can be reared in groups but also in isolation without added stress. This is a critical but rarely met requirement for experimentally varying the social environment to test its impact on cognition. We split broods of spiders and reared them either in a physically or in a socially enriched environment. A third group kept under completely deprived conditions served as a ‘no-enrichment’ control. We tested the spiders’ learning abilities by using a modified T-maze. Social behaviour was investigated by confronting spiders with their own mirror image. Results show that spiders reared in groups outperform their conspecifics from the control, i.e. ‘no-enrichment’, group in both tasks. Physical enrichment did not lead to such an increased performance. We therefore tentatively suggest that growing up in contact with conspecifics induces the development of cognitive abilities in this species.
Early social environment can play a significant role in shaping behavioural development. For instance, in many social mammals and birds, isolation rearing results in individuals that are less exploratory, shyer, less social and more aggressive than individuals raised in groups. Moreover, dynamic aspects of social environments, such as the nature of relationships between individuals, can also impact the trajectory of development. We tested if being raised alone or socially affects behavioural development in the family-living tree skink, Egernia striolata. Juveniles were raised in two treatments: alone or in a pair. We assayed exploration, boldness, sociability and aggression repeatedly throughout each juvenile's first year of life, and also assessed social interactions between pairs to determine if juveniles formed dominant–subordinate relationships. We found that male and/or the larger skinks within social pairs were dominant. Developing within this social environment reduced skink growth, and subordinate skinks were more prone to tail loss. Thus, living with a conspecific was costly for E. striolata. The predicted negative effects of isolation failed to materialize. Nevertheless, there were significant differences in behavioural traits depending on the social environment (isolated, dominant or subordinate member of a pair). Isolated skinks were more social than subordinate skinks. Subordinate skinks also became more aggressive over time, whereas isolated and dominant skinks showed invariable aggression. Dominant skinks became bolder over time, whereas isolated and subordinate skinks were relatively stable in their boldness. In summary, our study is evidence that isolation rearing does not consistently affect behaviour across all social taxa. Our study also demonstrates that the social environment plays an important role in behavioural development of a family-living lizard.
The social environment early in life is a key determinant of developmental, physiological and behavioural trajectories across vertebrate and invertebrate animals. One crucial variable is the presence/absence of conspecifics. For animals usually reared in groups, social isolation after birth or hatching can be a highly stressful circumstance, with potentially long-lasting consequences. Here, we assessed the effects of social deprivation (isolation) early in life, that is, absence of conspecifics, versus social enrichment, that is, presence of conspecifics, on developmental time, body size at maturity, mating behaviour and group-living in the plant-inhabiting predatory mite Phytoseiulus persimilis. Socially deprived protonymphs developed more slowly and were less socially competent in grouping behaviour than socially enriched protonymphs. Compromised social competence in grouping behaviour was evident in decreased activity, fewer mutual encounters and larger interindividual distances, all of which may entail severe fitness costs. In female choice/male competition, socially deprived males mated earlier than socially enriched males; in male choice/female competition, socially deprived females were more likely to mate than socially enriched females. In neither mate choice situation did mating duration or body size at maturity differ between socially deprived and enriched mating opponents. Social isolation-induced shifts in mating behaviour may be interpreted as increased attractiveness or competitiveness or, more likely, as hastiness and reduced ability to assess mate quality. Overall, many of the social isolation-induced behavioural changes in P. persimilis are analogous to those observed in other animals such as cockroaches, fruit flies, fishes or rodents. We argue that, due to their profound and persistent effects, early social deprivation or enrichment may be important determinants in shaping animal personalities.
Background
Individual differences in behaviour are widespread in the animal kingdom and often influenced by the size or composition of the social group during early development. In many vertebrates the effects of social interactions early in life on adult behaviour are mediated by changes in maturation and physiology. Specifically, increases in androgens and glucocorticoids in response to social stimulation seem to play a prominent role in shaping behaviour during development. In addition to the prenatal and early postnatal phase, adolescence has more recently been identified as an important period during which adult behaviour and physiology are shaped by the social environment, which so far has been studied mostly in mammals. We raised zebra finches (Taeniopygia guttata) under three environmental conditions differing in social complexity during adolescence - juvenile pairs, juvenile groups, and mixed-age groups - and studied males’ behavioural, endocrine, and morphological maturation, and later their adult behaviour.
Results
As expected, group-housed males exhibited higher frequencies of social interactions. Group housing also enhanced song during adolescence, plumage development, and the frequency and intensity of adult courtship and aggression. Some traits, however, were affected more in juvenile groups and others in mixed-age groups. Furthermore, a testosterone peak during late adolescence was suppressed in groups with adults. In contrast, corticosterone concentrations did not differ between rearing environments. Unexpectedly, adult courtship in a test situation was lowest in pair-reared males and aggression depended upon the treatment of the opponent with highest rates shown by group-reared males towards pair-reared males. This contrasts with previous findings, possibly due to differences in photoperiod and the acoustic environment.
Conclusion
Our results support the idea that effects of the adolescent social environment on adult behaviour in vertebrates are mediated by changes in social interactions affecting behavioural and morphological maturation. We found no evidence that long-lasting differences in behaviour reflect testosterone or corticosterone levels during adolescence, although differences between juvenile and mixed-age groups suggest that testosterone and song behaviour during late adolescence may be associated.
Reptiles and Amphibians of Australia is a complete guide to Australia’s rich and varied herpetofauna, including frogs, crocodiles, turtles, tortoises, lizards and snakes. For each of the 1218 species there is a description of its appearance, distribution and habits. Each species is accompanied by a distribution map and, in most cases, a colour photograph of the living animal. The book includes 130 simple-to-use dichotomous keys that in most cases allow a specimen in hand to be identified. In addition, it has a comprehensive list of scientific references for those wishing to conduct more in-depth research, an extensive glossary, and basic guides to the collection, preservation and captive care of specimens. This classic work, originally published in 1975, has been completely brought up to date. This seventh edition includes all species described prior to October 2013.
Darwin famously described special difficulties in explaining social evolution in insects. More than a century later, the evolution of sociality - defined broadly as cooperative group living - remains one of the most intriguing problems in biology. Providing a unique perspective on the study of social evolution, this volume synthesizes the features of animal social life across the principle taxonomic groups in which sociality has evolved. The chapters explore sociality in a range of species, from ants to primates, highlighting key natural and life history data and providing a comparative view across animal societies. In establishing a single framework for a common, trait-based approach towards social synthesis, this volume will enable graduate students and investigators new to the field to systematically compare taxonomic groups and reinvigorate comparative approaches to studying animal social evolution.
