BACKGROUND Access to oestrus females tends to be the main driver of male sociality. This factor can lead to complex behavioural interactions between males and groups of males. Male bottlenose dolphins may form alliances to consort females and to compete with other males. In some populations these alliances may form temporary coalitions when competing for females. I examined the role of dyadic a...

Cooperative behaviour through reciprocation or interchange of valuable services in primates has received considerable attention, especially regarding the timeframe of reciprocation and its ensuing cognitive implications. Much less, however, is known about reciprocity in other animals, particularly birds. We investigated patterns of agonistic support (defined as a third party intervening in an o...

Receiver bias models of signal evolution are typically regarded as alternatives or complements to ornament evolution due to coevolving mate choice, whereas sexually or socially selected agonistic signals are rarely studied with respect to receiver psychology. Against the background of convergent evolution of red agonistic signals from yellow ancestors in the genus Euplectes (widowbirds and bish...

The idea that competition and aggression are central to an understanding of the origins of group-living and sociality among human and nonhuman primates is the dominant theory in primatology today. Using this paradigm, researchers have focused their attention on competitive and aggressive behaviors, and have tended to overlook the importance of cooperative and affiliative behaviors. However, coo...

OBJECTIVE To evaluate the presence of a dominance rank in a group of cats and the relation between agonistic behavior and the use of resources, including environmental enrichment, in these cats. DESIGN Observational analytic study. ANIMALS 27 neutered cats in a shelter in Sao Paulo, Brazil. PROCEDURES The cats were video recorded for 4 consecutive days to obtain baseline data. Subsequentl...

BACKGROUND Eriosema laurentii De Wild. (Leguminosae) is a plant used in Cameroon against infertility and gynecological or menopausal complaints. In our previous report, a methanol extract of its aerial parts was shown to exhibit estrogenic and aryl hydrocarbon receptor agonistic activities in vitro and to prevent menopausal symptoms in ovariectomized Wistar rats. METHODS In order to determine...