Paternal kin discrimination using acoustic cues
Final Report Abstract
Recognizing kin allows individuals to favor them in social interactions and avoid matings with close relatives, behaviors that can increase inclusive fitness. Among rhesus macaques (Macaca mulatta) strong evidence exists that (i) maternally related females recognize each other using acoustic cues and (ii) that most likely familiarity is the underlying mechanism to identify maternal kin. Mechanisms allowing recognition of paternal relatives are of particular interest, as the promiscuous mating system found in many species is less likely to provide paternity information via social familiarity. However, behavioral observations indicate that semi free-ranging female rhesus macaques prefer to associate with their paternal half-sisters in comparison to unrelated females within the same group, particularly when born within the same age cohort. Nevertheless, the cues and mechanism/s used in paternal kin discrimination remained under debate. This project was set up to test (i) whether information signaling relatedness is encoded in the acoustic structure of rhesus macaque vocalizations, (ii) to clarify the mechanism underlying paternal kin discrimination (with familiarity and phenotype matching being the most likely mechanisms), and to test (iii) whether males (the migrating and therefore less socially integrated sex) also use the acoustic cue to identify their kin (maternal and paternal). For this proposes we combined fine-tuned acoustic analyses with detailed data on genetic relatedness. The uses of the acoustic cue, as well as the underlying mechanisms were investigated conducting playback experiments. Results indicate that female rhesus macaques are able to vocally identify their paternal sisters even when unfamiliar, supporting phenotype matching as the underlying mechanism. Contrary, we found male rhesus macaques to vocally recognize their maternal, but not paternal, kin, with this finding being the first demonstration of acoustic kin recognition by males in this species. However, structure analysis revealed no significant correlation between call similarity and degree of relatedness. We argue that the effect of gaining more similar call structure while growing up in the same cohort might override the call similarities of related females (sensu vocal accommodation), making it particularly difficult for currently available methodologies to disentangle relatedness and familiarity in the vocal structure. Besides new insights into the use of the acoustic cue and the underlying mechanisms of kin recognition, our project initiated a side project investigating the use of facial information to identify unfamiliar paternal kin. Here we found a systematic bias in looking time in relation to kinship status of the images presented (paternally related vs. unrelated), providing strong evidence for visual phenotype matching. Results of this project represent the first demonstration of spontaneous discrimination of own unfamiliar paternal kin on the basis of facial cues under natural conditions in any non-human primate. In conclusion, this project revealed new insights into the cues used and the underlying mechanisms of (in particular paternal) kin discrimination. The challenge for the future is to investigate whether the use of relatedness cues is related to fitness benefits.
Publications
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2010. Paternal kin discrimination in rhesus macaques (Macaca mulatta) - Identification of cues and mechanisms. Kyoto, the 23rd Congress of the International Primatological Society
Pfefferle, D. & Widdig A.
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2012. Kin discrimination in rhesus macaques (Macaca mulatta) using the acoustic modality. Cancun, the 24th Congress of the International Primatological Society
Pfefferle, D., Ruiz-Lambides, A. V. & Widdig A.
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2013. Paternal kin bias in primates: development, mechanisms and cues, San Juan, 37th meeting of the American Society of Primatology
Widdig, A.
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2013. Visual phenotype matching: cues to paternity are present in rhesus macaque faces. Newcastle Gateshead, joint meeting of the 33rd International Ethological Conference and the Association for the Study of Animal Behaviour
Kazem, A. J. N., Pfefferle, D., & Widdig A.
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2014. Monkeys spontaneously discriminate their unfamiliar paternal kin under natural conditions using facial cues. Current Biology 24:1806–1810
Pfefferle, D., Kazem, A. J. N., Brockhausen, R. R., Ruiz-Lambides, A. V. & Widdig, A.
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2014. Rhesus macaque females (Macaca mulatta) discriminate paternal siblings in playback experiments - support for phenotype matching. Proceedings of the Royal Society of London Series B 281, 20131628
Pfefferle, D., Ruiz-Lambides, A. V. & Widdig, A.
