Table 6.

Summary of the similarities and differences in parameters affecting association patterns in bonobos and chimpanzees. M: males, F: females, ‘X → Y’ indicates from X towards Y (e.g. M → F = from males towards females). TA: top associates. SA: significant associates. ∼: similar.

species
parametersbonoboschimpanzeesdifferences/interpretation
sex combinationnot controlling for kinshipTA
  1. M–F > M–M

  2. F–F > F–M

  1. M–M > M–F

  2. F–F > F–M

In both species, females were more often significant and top associates of other females than males. The species, however, differed for males’ top and significant associates, being primarily males in chimpanzees and primary females in bonobos.
SA
  1. M–F > M–M

  2. F–F > F–M

  1. M–M > M–F

  2. F–F > F–M

controlling for kinshipTAM–M ∼ M–F ∼ F–FM–M > F–F & F–MWhen controlling for kinship, the sex-specific association pattern holds for chimpanzees, with males primarily associating with other males and females with females. However, the pattern changed for bonobos and neither male nor female bonobos were more likely to have top or significant associates of a particular sex, after controlling for kinship.
SAM–M ∼ M–F ∼ F–FM–M > F–F > F–M
association skewmost skewed associationsM → FF → FA high association skew indicates that individuals were highly differentiated in their association partners of a given sex, i.e. they associate strongly with a few partners and weakly with the others. Conversely, a low association skew indicates that individuals were little differentiated in their association partners of a given sex, i.e. they associated relatively equally with all individuals. The sex combination with the most skewed (i.e. differentiated) association distribution differed between the two species. In chimpanzees, the most differentiated associations were from females towards other females and the least differentiated association from males towards other males. For bonobos, associations were more differentiated from males towards females compared with all other sex combinations.
least skewed associationsM → M & F → FM → M
associate in the pastpositive effect on associationIndividuals' association in the past had a similar effect on current association in both species, indicating that association patterns were as stable in bonobos as in chimpanzees.
kinshippositive effect on association (stronger in bonobos)Kinship had a positive influence on association patterns in both species, but the effect tended to be stronger in bonobos, indicating that kinship might structure associations more in bonobos than in chimpanzees.