DIET OF WHITE-CHEEKED-SPIDER-MONKEYS (Ateles marginatus) IN CONTINOUS FORESTS AT THE CRISTALINO PRIVATE RESERVE (MATO GROSSO – BRAZIL)

Feeding ecology plays a key role in primate behavior. Highly frugivorous primates, such as spider monkeys, adapt their diet and foraging strategies in tropical rainforests according to the abundance and availability of fruit. We studied white-cheeked spider monkeys (Ateles marginatus), an Endangered primate species, over nine months in 2011-2012, in continuous forests at the Cristalino Private Natural Heritage Reserve, Brazil. We recorded 1,401 feeding events through scan sampling and 75 feeding events using all occurrences sampling. We also made ad libitum observations. Scan sampling showed that the most important resource in the diet was fruits (76.1%) followed by leaves (18.2%), with fruit consumption peaking in the rainy months (90.1%). Leaf consumption increased during the dry months (33.9%), as did consumption of other items such as seeds (4.7%). We identified 64 plant species and 22 morphospecies in the monkeys’ diet. Complementary ad libitum observations at the same site, from November 2022 to February 2024, and local ecological knowledge revealed an opportunistic behavior: ground-level foraging for aquatic macrophytes (Eichhornia spp.) along riverbanks. Our results show that Ateles marginatus is highly frugivorous, but eats a larger proportion of (presumably) less preferred food items in periods where fruit availability is likely to be lower. Such basic feeding ecology data are important to inform habitat restoration, and management and conservation initiatives for this Endangered primate. We highlight the need for more studies of the seasonality of feeding ecology in Ateles marginatus, to plan conservation and management strategies.