Data from: Translocation experiments show dialects are socially learned in marmoset monkeys

The acoustic properties of vocalizations in common marmosets differ
between populations. These differences may be the result of social vocal
learning, but they can also result from environmental or genetic
differences between populations. We performed translocation experiments to
separately quantify the influence of a change in the physical environment
(experiment 1), and a change in the social environment (experiment 2) on
the acoustic properties of calls from individual captive marmosets. If
population differences were due to genetic differences, we expected no
change in the vocalizations of the translocated marmosets. If differences
were due to environmental factors, we expected vocalizations to
permanently change contingent with environmental changes. If social
learning was involved, we expected that the vocalizations of animals
translocated to a new population with a different dialect would become
more similar to the new population. In experiment 1, we translocated
marmosets to a different physical environment without changing the social
composition of the groups or their neighbours. Immediately after the
translocation to the new facility, one out of three call types showed a
significant change in call structure, but 5-6 weeks later, the calls were
no longer different from before the translocation. Thus, the novel
physical environment did not induce long lasting changes in the
vocalizations of the marmosets. In experiment 2, we translocated marmosets
to a new population with a different dialect. Importantly, our previous
work had shown that these two populations differed significantly in
vocalization structure. The translocated marmosets were still housed in
their original social group, but after translocation they were surrounded
by the vocalizations from neighbouring groups of the new population. The
vocal distance between the translocated individuals and the new population
decreased for two out of three call types over 16 weeks. Thus, even
without direct social contact or interaction, the vocalizations of the
translocated animals converged towards the new population, indicating that
common marmosets can modify their calls due to acoustic input from
conspecifics alone, via crowd vocal learning. To our knowledge, this is
the first study able to distinguish between different explanations for
vocal dialects as well as to show crowd vocal learning in a primate
species.