David Gaynor

• University of Pretoria

In many cooperatively breeding mammals, an unrelated dominant pair monopolizes reproduction in the social group while subordinates help to raise their offspring. In Kalahari meerkats (Suricata suricatta), dominant males are usually immigrants while dominant females are natal animals that have not left the group where they were born. However, in aro...

Annual cycles in day length are an important consideration in seasonal analyses of behaviour. Seasonal variation in day length not only represents an ecological constraint on activity, but also imposes methodological restrictions on analyses. This paper examines the implications of monthly variation in day length using data from a troop of chacma b...

The willingness to utilise caves as shelters is held to have been important to early humans but dependent on pyrotechnology. Despite anecdotal evidence that non-human primates will also exploit caves there has as yet been no detailed account of such exploitation or of the reasons underlying it. Here we provide the first such data, on the frequency...

Seyfarth (1977, Journal of Theoretical Biology, 65, 671–698) proposed an influential model that explained the long-term patterning of grooming relationships between female primates in terms of an interaction between the idealized grooming objectives of females and competition for valuable grooming partners. A critical test of the model requires a d...

Measurement of reproductive skew in social groups is fundamental to understanding the evolution and maintenance of sociality, as it determines the immediate fitness benefits to helpers of staying and helping in a group. However, there is a lack of studies in natural populations that provide reliable measures of reproductive skew and the correlates...

Annual cycles in day length are an important consideration in any analysis of seasonal behaviour patterns, since they determine the period within which obligate diurnal or nocturnal animals must conduct all of their essential activities. As a consequence, seasonal variation in day length may represent an ecological constraint on behaviour, since sh...

We used data from a natural experiment on adult female chacma baboons, Papio cynocephalus ursinus, to test the hypothesis that variation in aggression through time influences patterns of grooming reciprocity within a social group. Owing to a change in the baboons' competitive regime, we were able to compare data from periods when aggression was hig...

In cooperatively breeding species, helpers and parents commonly face two decisions when they find a food item: first, whether to feed the item to a young group member or to eat it themselves; and second, which offspring to feed. Little is known about the factors that influence these decisions in cooperative mammals, though optimal foraging theory p...

In vertebrate societies where young are reared communally, nonbreeding helpers are usually closely related to young but often vary widely in their contributions to feeding them. Evolutionary explanations of helping behaviour have focused on whether differences in the level of contributions between helpers are related to variation in kinship. We inv...

“Limited control” models of reproductive skew in cooperative societies suggest that the frequency of breeding by subordinates is determined by the outcome of power struggles with dominants. In contrast, “optimal skew” models suggest that dominants have full control of subordinate reproduction and allow subordinates to breed only when this serves to...

Evolutionary explanations of cooperative breeding based on kin selection have predicted that the individual contributions made by different helpers to rearing young should be correlated with their degree of kinship to the litter or brood they are raising. In the cooperative mongoose or meerkat, Suricata suricatta, helpers babysit pups at the natal...

1. In social mammals where group members cooperate to detect predators and raise young, members of small groups commonly show higher mortality or lower breeding success than members of large ones. It is generally assumed that this is because large group size allows individuals to detect or repel predators more effectively but other benefits of grou...

Like humans engaged in risky activities, group members of some animal societies take turns acting as sentinels. Explanations of the evolution of sentinel behavior have frequently relied on kin selection or reciprocal altruism, but recent models suggest that guarding may be an individual's optimal activity once its stomach is full if no other animal...

Summary In most respects, the demography of Kalahari suricates (Suricata suricatta) resembles that of other social mongooses. Average group size varies from four to nine, and groups typically include several mature females, of which one is responsible for the majority of breeding attempts. Breeding females show a postpartum oestrus; gestation is ar...

In cooperative groups of suricates (Suricata suricatta), helpers of both sexes assist breeding adults in defending and feeding pups, and survival rises in larger groups. Despite this, dominant breeding females expel subordinate females from the group in the latter half of their (own) pregnancy apparently because adult females sometimes kill their p...

Functional interpretations of helping behaviour suggest that it has evolved because helpers increase their direct or indirect fitness by helping. However, recent critiques have suggested that helping may be an unselected extension of normal parental behaviour, pointing to evidence that all mature individuals commonly respond to begging young (wheth...

Cheek pouches, one of the distinguishing characters of the Cercopithecinae, are structures used for the temporary storage of food. Their size and frequency of use within a given species are related primarily to the amount of conspecific competition for food. In relation to total body size, members of the genusPapio are considered to have relatively...