Socially induced flexibility in vocal production in wild meerkats (#3)
Although a growing body of data suggests animals possess some control over the production of their calls, the acoustic structure of vocalisations of terrestrial mammals is largely considered to be innate and inflexible. Kalahari meerkats (Suricata suricatta) are highly social, cooperative breeding mammals that live in groups composed of a dominant pair, subordinate helpers and dependent young. While the breeding female is dominant above all other individuals, subordinate females also seem to establish dominance relationships amongst each other, with older and heavier individuals being higher-ranked. However, agonistic events between subordinates are rare and more subtle mechanisms seem to be used in the maintenance of these hierarchies. Meerkats have a rich vocal repertoire, which they use to coordinate spatial organisation and mediate social interactions. All group members frequently produce close calls during foraging, thought to play a key role in maintaining group cohesion as well as in spacing individuals, presumably minimizing food competition. Close calls are individual-specific, but the degree of individual flexibility in call production remains unclear. Given their importance in mediating interactions during foraging, we predicted that close call structure might reflect the transient nature of encounters between subordinate females of different ranks. Here we show that both call rate and temporal parameters of calls produced by subordinate females change flexibly, reflecting 1) the distance to the nearest adult female, 2) the relative rank of the producer, and 3) the relative rank of its female neighbour. Furthermore, younger, lower ranked females, show a greater degree of vocal adjustment in response to their nearest female neighbour. Our findings show an undocumented degree of individual flexibility in call production, and suggest a mechanism through which dominance hierarchies among subordinates may be subtly maintained in mammalian societies.