Geophagy in large-headed capuchin monkeys (Sapajus apella macrocephalus) in the Reserva Nacional Tambopata, Peru

Many primate species have been observed descending to the forest floor to intentionally consume soil (geophagy) at licks. The practice of geophagy is assumed to provide health benefits, such as mineral supplementation and/or gastrointestinal tract protection. We collected data on geophagy events through the use of camera traps at Tambopata National Reserve in southeastern Peru. Two geophagy sites were monitored for 42 months, during which time we observed repeated geophagy events by a group of large-headed capuchin monkeys (Sapajus apella macrocephalus). To the best of our knowledge, this is the first report of its kind for the species. Geophagy was rare, with only 13 events recorded over the study period. All but one event took place during the dry season, and 85% of events took place in the late afternoon between 1600 and 1800 hours. The monkeys were observed consuming soil both in situ and ex situ, and displayed heightened vigilance behavior during geophagy events. Although the small sample size makes it difficult to draw clear conclusions as to the drivers of this behavior, the seasonal timing of the events and the high percentage of clay in the consumed soils suggest that these events are linked to the detoxification of secondary plant compounds in the monkeys' diet.