Chimpanzee fathers bias their behaviour towards their offspring

Abstract

Promiscuous mating was traditionally thought to curtail paternal investment owing to the potential costs of providing care to unrelated infants. However, mounting evidence suggests that males in some promiscuous species can recognize offspring. In primates, evidence for paternal care exists in promiscuous Cercopithecines, but less is known about these patterns in other taxa. Here, we examine two hypotheses for paternal associations with lactating mothers in eastern chimpanzees (Pan troglodytes schweinfurthii): paternal effort, whereby males associate and interact more with their own infants, and mating effort, whereby males invest in mothers and offspring for mating privileges. We found that fathers associated more with their offspring than they did with non-kin infants, particularly early in life when infanticide risk is highest. Additionally, fathers and their infant offspring interacted more than expected. Notably, association between fathers and mother–infant pairs did not predict the probability of siring the mother's next offspring. Our results support the paternal effort, but not the mating effort hypothesis in this species. Chimpanzees are one of the most salient models for the last common ancestor between Pan and Homo, thus our results suggest that a capacity for paternal care, possibly independent of long-term mother–father bonds, existed early in hominin evolution.

Bystanders intervene to impede grooming in Western chimpanzees and sooty mangabeys

“…In chimpanzees, individuals who were within visual range of the focal (usually within a range of less than 50 m, average around 30 m) were recorded continuously and constituted the bystanders of a grooming bout. This is in line with the definition of ‘party’ used in different chimpanzee study sites [ 51 , 77 , 87 ]. For mangabeys, we recorded all individuals that appeared in visual range during a 5 min period, and considered these the bystanders for grooming of the focal in this time period.…”

Group augmentation, collective action, and territorial boundary patrols by male chimpanzees

“…We thus used a male's paternity success at the time of patrols to assess the relationship between short-term direct fitness benefits and patrol participation. Although promiscuous mating results in low paternity certainty, male chimpanzees may have some information about their overall paternity success based on their mating histories (48,49). Paternity success was positively and significantly related to patrol participation (Table 1).…”

Intra-community infanticide in wild, eastern chimpanzees: a 24-year review

“…Existing data provide mixed support for sexually selected infanticide. Evidence supporting this hypothesis has been reported for a variety of primate species (Daly and Wilson 1984;Watts 1989a;Borries et al 1999;Palombit et al 2000), but while some have argued that the sexual selection hypothesis explains within-community infanticide in chimpanzees (for example: Otali and Gilchrist 2006;Murray et al 2014Murray et al , 2016, any adaptive benefits should be reduced in species with multimale groups, such as chimpanzees, due to both higher paternity uncertainty making it more likely that a male will kill his own infant, and competition for any mating opportunity created. The sexual selection hypothesis has not yet been tested explicitly for chimpanzees, although male infanticide has been documented in several primate species which live in multi-male groups (for example: red colobus (Piliocolobus badius): Struhsaker and Leland 1985; Hanuman langurs (Semnopithecus entellus): Borries 1997; chacma baboons (Papio ursinus): Palombit et al 2000).…”