1Humboldt Center for Evolutionary Anthropology, Humboldt State University, 2Windward Islands Research and Education Foundation, St. George's University
Thursday All day, Clinch Concourse
Cercopithecus mona is one of the few guenon species that emits calls during copulation. Here, we describe the structure of copulation calls made by wild mona monkeys on Grenada and in Cameroon. Analog recordings were digitized and then analyzed using Raven Pro v.1.4. The copulation calls have two components: grunts, given by males, and warbles, given by females. Each component is emitted multiple times during heterosexual copulatory bouts. The total number of times each component is given per bout is highly variable, as is the relationship between the two components. The grunt is a tonal, short-duration (x̅ = 0.097 sec), low-frequency call (below ca. 3 kHz) that is similar to calls given in other contexts. In comparison, the warble is a frequency-modulated, longer-duration call (x̅ = 0.652 sec) that is easily recognizable. Warbles show greater variation than grunts; they typically include three harmonics below 4 kHz, but can include higher frequencies. The distinctiveness of warbles compared to grunts suggests that a primary function of the mona copulation call may be to increase female reproductive success. Studies of other monkeys support this hypothesis; however, common explanations such as increased mating partners (sperm competition), increased parental investment, decreased infanticide, and the encouragement of synchronous breeding do not make sense for mona monkeys that have small testicles, little male parental investment or infanticide, and year-round breeding (on Grenada). Given that copulation calls are so rare among the genus, additional field studies are warranted to determine the function of these calls in C. mona.