Around 1,000 rhesus macaques inhabit the aptly named ‘Monkey Island’ off Puerto Rico. Their ancestors were originally imported from India in 1938 for scientific research, and they remain one of the most studied rhesus monkey populations in the world. In a new PLOS ONE study, Dana Pfefferle and colleagues took advantage of the extensive genetic data available for these primates to examine how genetic relatedness influences their communication.
Previous work had indicated that female rhesus macaques pay more attention to ‘coo’ calls from unfamiliar but related females than to calls from unrelated strangers. The authors predicted that relations might share similar call structures, allowing discrimination of kin from non-kin. To test this, they analyzed the acoustic structure of calls of 67 adult female macaques from Monkey Island.
The researchers were surprised to find that relatedness did not in fact predict coo similarity. However, age and familiarity did: females who were of similar age or who shared the same living group had similar coo call structure. This suggests that the macaques’ experience and social interactions have more effect than genetics in shaping their calls, and they likely do not use similar call structure to identify relations.
Just as human immigrants can find themselves picking up the native accent, this study suggests that monkeys may exhibit vocal accommodation, adapting their calls to be more similar to those of monkeys with whom they interact more frequently. The authors therefore note that further studies of kin recognition mechanisms should “fully control for the prominent effect of familiarity on the acoustic structure” by focusing on calls between unfamiliar kin.
Research Article: Pfefferle D, Hammerschmidt K, Mundry R, Ruiz-Lambides AV, Fischer J, Widdig A (2016) Does the Structure of Female Rhesus Macaque Coo Calls Reflect Relatedness and/or Familiarity? PLoS ONE 11(8): e0161133. doi:10.1371/journal.pone.0161133