Sexual dimorphism in chimpanzee (Pan troglodytes schweinfurthii) and human age-specific fertility.

Across vertebrates, species with intense male mating competition and high levels of sexual dimorphism in body size generally exhibit dimorphism in age-specific fertility. Compared with females, males show later ages at first reproduction and earlier reproductive senescence because they take longer to attain adult body size and musculature, and maintain peak condition for a limited time. This normally yields a shorter male duration of effective breeding, but this reduction might be attenuated in species that frequently use coalitionary aggression.

Inbreeding risk and maternal support have opposite effects on female chimpanzee dispersal.

Sex-biased dispersal is usually driven by a combination of inbreeding avoidance and intrasexual competition. Walker and Pusey show that dispersal decisions in chimpanzees are most influenced by inbreeding avoidance and kin cooperation, instead of competition.

What influences a pet dog's first impression of a stranger?

Dogs live in the dynamic human social networks full of strangers, yet they form strong and selective bonds with familiar caretakers. Little is known about how a bond is initially formed between a dog and a complete stranger. The first-impression hypothesis suggests that interacting with strangers can present an opportunity to form a mutualistic partnership.

Morphological Identification of Hair Recovered from Feces for Detection of Cannibalism in Eastern Chimpanzees.

Chimpanzees (Pan troglodytes) are primarily frugivorous but consume a variable amount of meat from a variety of organisms, including other chimpanzees. Cannibalism is rare, usually follows lethal aggression, and does not occur following natural deaths. While chimpanzee cannibalism has been documented at multiple sites, many instances of this behavior go unrecorded.

Maturation is prolonged and variable in female chimpanzees.

Chimpanzees are important referential models for the study of life history in hominin evolution. Age at sexual maturity and first reproduction are key life history milestones that mark the diversion of energy from growth to reproduction and are essential in comparing life history trajectories between chimpanzees and humans. Yet, accurate information on ages at these milestones in wild chimpanzees is difficult to obtain because most females transfer before breeding.

Chimpanzees breed with genetically dissimilar mates.

Inbreeding adversely affects fitness, whereas heterozygosity often augments it. Therefore, mechanisms to avoid inbreeding and increase genetic distance between mates should be advantageous in species where adult relatives reside together. Here we investigate mate choice for genetic dissimilarity in chimpanzees, a species in which many females avoid inbreeding through dispersal, but where promiscuous mating and sexual coercion can limit choice when related adults reside together.

Chimpanzee females queue but males compete for social status.

Dominance hierarchies are widespread in animal social groups and often have measureable effects on individual health and reproductive success. Dominance ranks are not static individual attributes, however, but instead are influenced by two independent processes: 1) changes in hierarchy membership and 2) successful challenges of higher-ranking individuals. Understanding which of these processes dominates the dynamics of rank trajectories can provide insights into fitness benefits of within-sex competition.