Mentor: Kelsey Ellis, Ph.D.

The loss of primary habitat around the world is causing a dramatic decline in species populations and rainforest diversity, with primate populations being particularly susceptible. By understanding how species currently coexist we may better understand how they will adapt to changing landscapes in the future. We examined niche partitioning among three closely-related, large-bodied primates (Alouatta seniculus, Ateles belzebuth, and Lagothrix lagotricha poeppigii) with overlapping home ranges at the Tiputini Biodiversity Station between June and July 2025, a period typically known for low fruit availability. On each day of observation, individuals from at least two different primate species were followed simultaneously, with behavioral data collected through a combination of full day or 1-hr focal animal sampling with 5-min instantaneous scan sampling. Biological samples of plant material eaten by these primates were recorded and photographed. Both Alouatta and Ateles spent a large portion of their observed time resting (62.9% of 202 scans and 43.5% of 1199 scans, respectively), whereas Lagothrix spent more time moving (32.8% of 1428 scans) and feeding (21.2%). When feeding on fruits, Ateles and Alouatta primarily fed on Ficus, while Lagothrix primarily fed on Spondias. Ateles also consumed much more palm fruit with larger seeds (Oenocarpus and Iriartea) than the other two species. These three primate species exhibit dietary and behavioral niche partitioning, with Lagothrix functioning as generalists with a broader diet and more evenly distributed activity budget. In contrast, Alouatta and Ateles appear to conserve energy by resting more, likely reflecting their specialization on foods such as leaves and specific fruit types that require longer digestion or less frequent foraging movements.

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