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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