Spider monkeys lower their 'whinnies' when making long-distance calls

Lower-frequency calls favored by isolated spider monkeys get faster responses from listeners in their group

Date:  April 3, 2019

Source:  PLOS

Isolated spider monkeys (Ateles geoffroyi) likely lower the pitch of their calls to improve the chances of re-establishing contact with their group, according to a study published April 3, 2019 in the open-access journal PLOS ONE by José D. Ordóñez-Gómez from the German Primate Center, Germany, and colleagues.

Spider monkeys live in groups and communicate with out-of-sight group members using vocalizations known as whinnies. They are known to vary the pitch, or frequency, of their whinnies, and in this study, the authors analyzed whether such variation relates to the relative social isolation of the caller. They also assessed whether listener responses changed depending on the frequency of the original whinny.

Between February and June of 2016, the authors followed a group of 27 female and 8 male adult black-handed spider monkeys in the Lacandona Rainforest of Mexico, recording the monkeys whenever they came within 20 meters of their microphones. For the purposes of this study, callers were defined as isolated if more than 40m from other adult monkeys -- otherwise, the caller was defined as being within a subgroup.

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