Mutual grooming functions to prolong grooming received in ringtailed lemurs

Mutual (simultaneous) grooming occurs in a variety of mammals and is characterized by a distinct payoff structure compared to unidirectional grooming, as in mutual (but not in unidirectional) grooming both partners simultaneously get the benefits of the receipt of grooming. Mutual grooming, however, has been very little investigated. We studied a captive group of ringtailed […]

The effects of unequal reward distributions on cooperative problem solving by cottontop tamarins, Saguinus oedipus

Cooperation among nonhuman animals has been the topic of much theoretical and empirical research, but few studies have examined systematically the effects of various reward payoffs on cooperative behaviour. Here, we presented heterosexual pairs of cooperatively breeding cottontop tamarins with a cooperative problem-solving task. In a series of four experiments, we examined how the tamarins’ […]

The influence of kin relationship and reciprocal context on chimpanzees’ other-regarding preferences

We investigated the evolutionary origin of other-regarding preferences, one of the strong underlying motivations for altruism, in the chimpanzee, Pan troglodytes. Although altruism is expected theoretically to be kin biased and frequent in a reciprocal context, few experimental studies to date have specifically tested these hypotheses from the viewpoint of proximate mechanisms. We examined the […]

Token transfers among great apes (Gorilla gorilla, Pongo pygmaeus, Pan paniscus, and Pan troglodytes): Species differences, gestural requests, and reciprocal exchange

Great apes appear to be the nonhuman primates most capable of recognizing trading opportunities and engaging in transfers of commodities with conspecifics. Spontaneous exchange of goods between them has not yet been reported. We tested gorillas (Gorilla gorilla), orangutans (Pongo pygmaeus), bonobos (Pan paniscus), and chimpanzees (Pan troglodytes) in a token-exchange task involving two conspecifics […]

Reciprocity of support in coatis (Nasua nasua)

Primate sociality has received much attention and its complexity has been viewed as a driving force for the evolution of cognitive abilities. Improved analytic techniques have allowed primate researchers to reveal intricate social networks based on the exchange of cooperative acts and services. Although nonprimates are known to show similar behavior (e.g., cooperative hunting, food […]

The influence of the steepness of dominance hierarchies on reciprocity and interchange in captive groups of bonobos (Pan paniscus)

Biological market models explain variability in reciprocity and interchange between groups. In groups with a shallow dominance gradient, grooming will be mostly exchanged for itself (i.e. exchange will occur). In groups with steep dominance hierarchies, interchange is expected: individuals will groom higher ranking individuals to get access to limited resources or commodities such as support […]

Chimpanzees share food for many reasons: the role of kinship, reciprocity, social bonds and harassment on food transfers

There is currently great interest in the phylogenetic origins of altruistic behaviour within the primate order. Considerable attention has been focused on chimpanzees, Pan troglodytes, because they are our closest living relatives and participate in a wide range of collective activities, including hunting and food sharing. Food sharing is of particular importance because it plays […]

Social instability raises the stakes during social grooming among wild male chimpanzees

Explaining cooperative behaviour is a fundamental issue for evolutionary biology. The challenge for any cooperative strategy is to minimize the risks of nonreciprocation (cheating) in interactions with immediate costs and delayed benefits. One of a variety of proposed strategies, the raise-the-stakes (RTS) strategy, posits that individuals establish cooperation by increasing investment across interactions from an […]

Grooming reciprocity in male Tibetan macaques

In several primate species, adult males are reported to compete for access to reproductive partners as well as forming affiliative and cohesive social bonds based on the exchange of goods or services. We hypothesized that among a broad set of fitness-maximizing strategies, grooming can be used by individual adult males to enhance social relationships through […]

Stealing milk by young and reciprocal mothers: high incidence of allonursing in giraffes, Giraffa camelopardalis

Allonursing, the nursing of nonfilial offspring, has been reported in a number of mammalian species; however, very few studies have investigated more than three hypotheses. The aim of our study was to investigate seven hypotheses explaining allonursing in captive giraffes. During 2007–2011, we observed 24 females and 37 calves in four zoological gardens in the […]