Systematic mapping of developmental milestones in wild chimpanzees

ostnatal development is protracted relative to lifespan in many primates, including modern humans (Homo sapiens ), facilitating the acquisition of key motor, communication and social skills that can maximise fitness later in life. Nevertheless, it remains unclear what evolutionary drivers led to extended immature periods. While the developmental milestone literature is well established in humans, insight we can gain from one‐species models is limited. By comparing the timing of relatable developmental milestones in a closely related species, the chimpanzee (Pan troglodytes ), we can gain further understanding of the evolution of such an extended developmental phase. To date, few studies have specifically attempted to estimate developmental milestones in a manner comparable to the human literature, and existing studies lack sufficient sample sizes to estimate which milestones are more plastic with higher inter‐individual variation in the timing of their emergence. Here, we describe the emergence of gross motor, fine motor, social interaction and communication traits from a longitudinal sample of 19 wild chimpanzee infants (8 females and 11 males), Taï National Park, Côte d’Ivoire. Gross motor traits emerged at a mean of four months, communication traits at 12 months, social interaction traits at 14 months and fine motor traits at 15 months, with later emerging milestones demonstrating greater inter‐individual variation in the timing of the emergence. This pattern of milestone emergence is broadly comparable to observations in humans, suggesting selection for a prolonged infantile phase and that sustained skills development has a deep evolutionary history, with implications for theories on primate brain development

No pain, no gain: insights into changing individual volitional behaviour

Physical activity is an important component of a healthy lifestyle. The purpose of this study is threefold: first, to empirically examine the effect of attitudes on people's intentions towards starting a new physical activity in three weight groups; second, to explore differences within various demographic groups; and finally, to offer research and practical implications for social marketers who are working in the area of physical activity. A total of 1459 respondents participated in an online survey. Our findings indicate that when individuals hold both negative and positive attitudes towards physical activity, they will have higher intentions to start a new physical activity. Empirical examination identified that overweight and obese people have more negative and less positive attitudes than healthier people toward physical activity. The results indicate that overcoming negative attitudes and reinforcing positive attitudes remain as a necessary condition to influence volitional behaviours such as physical activity, which requires cognitive processing and actions in order for the behaviour to be changed. People engaging in physical activities understand both positive and negative effects of physical activities, and they may engage in physical activities despite knowing there are short-term costs

Long-term repeatability in social behaviour suggests stable social phenotypes in wild chimpanzees

Consistent individual differences in social phenotypes have been observed in many animal species. Changes in demographics, dominance hierarchies or ecological factors, such as food availability or disease prevalence, are expected to influence decision-making processes regarding social interactions. Therefore, it should be expected that individuals show flexibility rather than stability in social behaviour over time to maximize the fitness benefits of social living. Understanding the processes that create and maintain social phenotypes requires data encompassing a range of socioecological settings and variation in intrinsic state or life-history stage or strategy. Using observational data spanning up to 19 years for some individuals, we demonstrate that multiple types of social behaviour are repeatable over the long term in wild chimpanzees, a long-lived species with complex fission-fusion societies. We controlled for temporal, ecological and demographic changes, limiting pseudo-repeatability. We conclude that chimpanzees living in natural ecological settings have relatively stable long-term social phenotypes over years that may be independent of life-history or reproductive strategies. Our results add to the growing body of the literature suggesting consistent individual differences in social tendencies are more likely the rule rather than the exception in group-living animals

Repeatable glucocorticoid expression is associated with behavioural syndromes in males but not females in a wild primate

Behavioural syndromes are a well-established phenomenon in human and non-human animal behavioural ecology. However, the mechanisms that lead to correlations among behaviours and individual consistency in their expression at the apparent expense of behavioural plasticity remain unclear. The ‘state-dependent’ hypothesis posits that inter-individual variation in behaviour arises from inter-individual variation in state and that the relative stability of these states within an individual leads to consistency of behaviour. The endocrine stress response, in part mediated by glucocorticoids (GCs), is a proposed behavioural syndrome-associated state as GC levels are linked to an individual’s behavioural responses to stressors. In this study, in wild Barbary macaques (Macaca sylvanus), consistent inter-individual differences were observed in both sexes for GC activity (faecal glucocorticoid, fGC concentrations), but not GC variation (coefficient of variation in fGC concentrations). The expression of the behavioural syndrome ‘Excitability’ (characterized by the frequencies of brief affiliation or aggressive interactions) was related to GC activity in males but not in females; more ‘excitable’ males had lower GC activity. There was no relationship in females between any of the behavioural syndromes and GC activity, nor in either sex with GC variation. The negative relationship between GC activity and Excitability in males provides some support for GC expression as a behavioural syndrome-generating state under the state-dependent framework. The absence of this relationship in females highlights that state-behavioural syndrome associations may not be generalizable within a species and that broader sex differences in state need to be considered for understanding the emergence and maintenance of behavioural syndromes

Behavioural thermoregulation via microhabitat selection of winter sleeping areas in an endangered primate: implications for habitat conservation

Strategic microhabitat selection allows animals in seasonally cold environments to reduce homeostatic energy costs, particularly overnight when thermoregulatory demands are greatest. Suitable sleeping areas may therefore represent important resources for winter survival. Knowledge of microhabitat use and potential impacts of anthropogenic habitat modification can aid species conservation through development of targeted habitat management plans. Wild, endangered Barbary macaques (Macaca sylvanus) in logged cedar-oak forest were studied to investigate (1) the hypothesis that macaques select winter sleeping areas with microhabitat characteristics that may reduce thermoregulatory costs, and, if so, (2) how to minimize damage to sleeping areas from logging. Macaques slept only in Atlas cedars (Cedrus atlantica). Consistent with predictions, macaques preferred sleeping in sheltered topography and dense vegetation, which may reduce exposure to wind, precipitation and cold, and preferred large trees that facilitate social huddling. This suggests that Barbary macaques employ strategic nocturnal microhabitat selection to reduce thermoregulatory costs and thus suitable sleeping areas may influence winter survival. To minimize negative impacts of logging on macaque sleeping areas, results suggest avoiding logging in topographical depressions and maintaining cedar densities greater than 250 ha-1 with average breast height greater than 60 cm. This study demonstrates how animal behaviour can be used to guide species-specific habitat management plans

Behavioral responses to injury and death in wild Barbary macaques (Macaca sylvanus)

The wounding or death of a conspecific has been shown to elicit varied behavioral responses throughout thanatology. Recently, a number of reports have presented contentious evidence of epimeletic behavior towards the dying and dead among non-human animals, a behavioral trait previously considered uniquely human. Here, we report on the behavioral responses of Barbary macaques, a social, non-human primate, to the deaths of four group members (one high-ranking adult female, one high-ranking adult male, one juvenile male, and one female infant), all caused by road traffic accidents. Responses appeared to vary based on the nature of the death (protracted or instant) and the age class of the deceased. Responses included several behaviors with potential adaptive explanations or consequences. These included exploration, caretaking (guarding, carrying, and grooming), and proximity to wounded individuals or corpses, and immediate as well as longer-lasting distress behaviors from other group members following death, all of which have been reported in other non-human primate species. These observations add to a growing body of comparative evolutionary analysis of primate thanatology and help to highlight the multifaceted impacts of human-induced fatalities on an endangered and socially complex primate. © 2016, Japan Monkey Centre and Springer Japan

Patterns of urinary cortisol levels during ontogeny appear population specifi c rather than species specifi c in wild chimpanzees and bonobos

Compared with most mammals, postnatal development in great apes is protracted, presenting both an extended period of phenotypic plasticity to environmental conditions and the potential for sustained mother-offspring and/or sibling conflict over resources. Comparisons of cortisol levels during ontogeny can reveal physiological plasticity to species or population specific socioecological factors and in turn how these factors might ameliorate or exaggerate mother-offspring and sibling conflict. Here, we examine developmental patterns of cortisol levels in two wild chimpanzee populations (Budongo and Taï), with two and three communities each, and one wild bonobo population (LuiKotale), with two communities. Both species have similar juvenile life histories. Nonetheless, we predicted that key differences in socioecological factors, such as feeding competition, would lead to interspecific variation in mother-offspring and sibling conflict and thus variation in ontogenetic cortisol patterns. We measured urinary cortisol levels in 1394 samples collected from 37 bonobos and 100 chimpanzees aged up to 12 years. The significant differences in age-related variation in cortisol levels appeared population specific rather than species specific. Both bonobos and Taï chimpanzees had comparatively stable and gradually increasing cortisol levels throughout development; Budongo chimpanzees experienced declining cortisol levels before increases in later ontogeny. These age-related population differences in cortisol patterns were not explained by mother-offspring or sibling conflict specifically; instead, the comparatively stable cortisol patterns of bonobos and Taï chimpanzees likely reflect a consistency in experience of competition and the social environment compared with Budongo chimpanzees, where mothers may adopt more variable strategies related to infanticide risk and resource availability. The clear population-level differences within chimpanzees highlight potential intraspecific flexibility in developmental processes in apes, suggesting the flexibility and diversity in rearing strategies seen in humans may have a deep evolutionary history

Shared community effects and the non-genetic maternal environment shape cortisol levels in wild chimpanzees

Mechanisms of inheritance remain poorly defined for many fitness-mediating traits, especially in long-lived animals with protracted development. Using 6,123 urinary samples from 170 wild chimpanzees, we examined the contributions of genetics, non-genetic maternal effects, and shared community effects on variation in cortisol levels, an established predictor of survival in long-lived primates. Despite evidence for consistent individual variation in cortisol levels across years, between-group effects were more influential and made an overwhelming contribution to variation in this trait. Focusing on within-group variation, non-genetic maternal effects accounted for 8% of the individual differences in average cortisol levels, significantly more than that attributable to genetic factors, which was indistinguishable from zero. These maternal effects are consistent with a primary role of a shared environment in shaping physiology. For chimpanzees, and perhaps other species with long life histories, community and maternal effects appear more relevant than genetic inheritance in shaping key physiological traits