Early-life social experience affects offspring DNA methylation and later life stress phenotype.

Studies in rodents and captive primates suggest that the early-life social environment affects future phenotype, potentially through alterations to DNA methylation. Little is known of these associations in wild animals. In a wild population of spotted hyenas, we test the hypothesis that maternal care during the first year of life and social connectedness during two periods of early development leads to differences in DNA methylation and fecal glucocorticoid metabolites (fGCMs) later in life. Here we report that although maternal care and social connectedness during the den-dependent life stage are not associated with fGCMs, greater social connectedness during the subadult den-independent life stage is associated with lower adult fGCMs. Additionally, more maternal care and social connectedness after den independence correspond with higher global (%CCGG) DNA methylation. We also note differential DNA methylation near 5 genes involved in inflammation, immune response, and aging that may link maternal care with stress phenotype.

Reproduction Within a Hierarchical Society from a Female's Perspective.

The reproductive biology of many female mammals is affected by their social environment and their interactions with conspecifics. In mammalian societies structured by linear dominance hierarchies, such as that of the spotted hyena (Crocuta crocuta), a female's social rank can have profound effects on both her reproductive success and her longevity. In this species, social rank determines priority of access to food, which is the resource limiting reproduction. Due largely to rank-related variation in access to food, reproduction from the perspective of a female spotted hyena can only be understood in the context of her position in the social hierarchy. In this review, we examine the effects of rank on the various phases of reproduction, from mating to weaning. Summed over many individual reproductive lifespans, the effect of rank at these different reproductive phases leads to dramatic rank-related variation in fitness among females and their lineages. Finally, we ask why females reproduce socially despite these apparent costs of group living to low-ranking females. Gregariousness enhances the fitness of females regardless of their positions in the social hierarchy, and females attempting to survive and reproduce without clanmates lose all their offspring. The positive effects of gregariousness appear to result from having female allies, both kin and non-kin, who cooperate to advertise and defend a shared territory, acquire, and defend food resources, maintain the status quo, and occasionally also to rise in social rank.

Numerical assessment in the wild: insights from social carnivores.

Playback experiments have proved to be a useful tool to investigate the extent to which wild animals understand numerical concepts and the factors that play into their decisions to respond to different numbers of vocalizing conspecifics. In particular, playback experiments have broadened our understanding of the cognitive abilities of historically understudied species that are challenging to test in the traditional laboratory, such as members of the Order Carnivora. Additionally, playback experiments allow us to assess the importance of numerical information versus other ecologically important variables when animals are making adaptive decisions in their natural habitats. Here, we begin by reviewing what we know about quantity discrimination in carnivores from studies conducted in captivity. We then review a series of playback experiments conducted with wild social carnivores, including African lions, spotted hyenas and wolves, which demonstrate that these animals can assess the number of conspecifics calling and respond based on numerical advantage. We discuss how the wild studies complement those conducted in captivity and allow us to gain insights into why wild animals may not always respond based solely on differences in quantity. We then consider the key roles that individual discrimination and cross-modal recognition play in the ability of animals to assess the number of conspecifics vocalizing nearby. Finally, we explore new directions for future research in this area, highlighting in particular the need for further work on the cognitive basis of numerical assessment skills and experimental paradigms that can be effective in both captive and wild settings.This article is part of a discussion meeting issue 'The origins of numerical abilities'.

Limited social learning of a novel technical problem by spotted hyenas.

Social learning can have profound evolutionary consequences because it drives the diffusion of novel behaviours among individuals and promotes the maintenance of traditions within populations. We inquired whether spotted hyenas (Crocuta crocuta), generalist carnivores living in complex, primate-like societies, acquire information from conspecifics about a novel problem-solving task. Previously, we presented wild hyenas with a food-access puzzle and found that social learning opportunities did not affect problem-solving success among observers, but did reduce observers' neophobia. However, we had little control over which individuals observed conspecifics solve the problem, and few wild hyenas were successful. Therefore, we conducted an experiment in captivity where we controlled observer access to two demonstration styles. Again, social learning opportunities did not affect problem-solving success, but tended to reduce neophobia among captive observers. Social learning opportunities also influenced problem-solving style. Captive hyenas showed limited evidence for directed social learning; low-ranking individuals paid closer attention to demonstrators than high-ranking individuals, although this greater attention did not result in greater success. We conclude that wild and captive hyenas exploit social learning opportunities similarly, and that the limited social learning shown by hyenas on this task is likely based on localized stimulus enhancement.

Faunal assemblage composition and paleoenvironment of Plovers Lake, a Middle Stone Age locality in Gauteng Province, South Africa.

Plovers Lake is a dolomitic cave infill located approximately 45km northwest of Johannesburg in the Bloubank Valley, Gauteng Province, South Africa. Excavations between 2002-2004 revealed a rich and diverse fauna, a moderate-sized stone tool assemblage of Middle Stone Age (MSA) character, and human skeletal remains. Two principal depositional units are recognized: 1) a disturbed ex situ component that was likely displaced from 2) an otherwise relatively undisturbed in situ component from which the human skeletal material was recovered. The in situ depositional unit is bracketed by 2 flowstone layers, with U-series dates of 62.9 (+/-1.3)ka for the capping flowstone and 88.7 (+/-1.6)ka for the underlying flowstone. A single isochron ESR date of 75.6 (+/-5.6)ka corroborates the U-series dates. This paper presents an analysis of the mammalian, bird, and reptile faunas recovered from these two units. The two faunal assemblages show close correspondence in taphonomic, taxonomic, and ecological composition, supporting a common origin for both the ex situ and in situ components. Although human skeletal material, cut-marked bone, and stone tools have been recovered, these indications are too rare to consider Plovers Lake a human occupation site. Instead, a high abundance of carnivores, coprolites, and carnivore damaged bones point to brown hyenas as the principal, though not exclusive, bone accumulating agent. In the absence of a significant taphonomic bias relating to accumulating agent, Plovers Lake allows us to document an environment occupied by MSA humans, even if the humans were not resident in the cave itself. We reconstruct the paleoenvironment of Plovers Lake as predominantly grassland, though it was colder, moister, and more wooded than at present. Paleoclimatic conditions appear to have been as different from historic norms as those seen in several fossil localities in the Western Cape, pointing to greater environmental heterogeneity than has previously been documented for the region in the later Pleistocene.