Evidence for paternal kin bias in the social affiliation of adult female blue monkeys

• Published in: American journal of primatology Vol. 80; no. 5; pp. e22761 - n/a
• Main Authors: Cords, Marina, Minich, Taylor, Roberts, Su‐Jen, Sleator, Clio
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.05.2018
• Subjects: Acknowledgment; Adults; Bias; Breeding; Breeding of animals; Discrimination; Females; Fitness; Grooming; Juveniles; kin discrimination; Kin recognition; kin selection; kinship; Monkeys; Monkeys & apes; Nepotism; Phenotypes; Primates; Proximity; Recognition; Relatives; Siblings; social behavior; nepotism; kin discrimination; social behavior; kin selection; kinship
• ISSN: 0275-2565; 1098-2345; 1098-2345
• DOI: 10.1002/ajp.22761

If animals increase inclusive fitness by cooperating with relatives, nepotism should involve maternal and paternal kin equally, all else being equal. Evidence of a behavioral bias toward paternal half‐siblings in primates is both limited and mixed, with most positive reports from papionins. To expand knowledge of paternal kin recognition, particularly in cercopithecine monkeys, we examined evidence for paternal kin bias in wild blue monkeys (Cercopithecus mitis), a species living mostly in one‐male groups. Seasonal breeding and the amount of male reproductive skew in blue monkeys suggests that opportunities to distinguish paternal kin are plentiful, and their social system would make such discrimination beneficial. We compared spatial association and social contact (grooming and contact‐sitting) of 20 adult females with at least one paternal half‐sibling and at least one non‐relative that were present at the same time. We used two data sets, one in which social partners were other parous females, the other in which they were juveniles. Data came from a 7‐year period. When interacting with other adult females, subjects groomed and sat in contact with paternal half‐siblings significantly more than with known non‐kin, and there was a similar trend for spatial association. We detected no paternal kin bias in interactions with juvenile partners. Kin‐biased affiliative contact with adult female partners did not appear to be based on age proximity, measured by birth cohort. The study species’ social system suggests phenotype matching as the most likely alternative mechanism, though we could not test it directly. Across both behaviors, there was no significant relationship between the number of matrilineal kin a subject had and the degree to which she preferred paternal half‐siblings over non‐kin as affiliative partners. These findings contribute to a comparative understanding of paternal kin recognition in primates. HIGHLIGHTS • Blue monkey adult females interacting with peers prefer to socialize with paternalhalf‐siblings over known non‐relatives, suggesting an ability to recognize thesepaternal kin.• The mechanism of kin recognition does not appear to be based on age similarity.• The degree to which females preferred paternal half‐siblings was not related to thenumber matrilineal kin they had, or to the number of very close maternal relatives. Adult female blue monkeys show higher rates of social contact and association with paternal half‐siblingsthan with non‐relatives. Each line shows data for one adult female, and connects her average value forsocializing with partners in each class.