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Research Group
Research Group
Ashley Sideri
Ashley Sideri
Undergraduate, Zoology major, anthropology minor
Mary Lerch
Mary Lerch
Graduate student, Institute for the Environment and Sustainability Department
Dr. Kelsey Ellis
Dr. Kelsey Ellis
Department of Anthropology
Abstract
Abstract
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.
Key words: niche partitioning, diet, activity, Atelidae, interspecific competition, Amazonian Ecuador
Background
Background
One way species may reduce interspecific competition is through niche partitioning such as differences in diet (especially during periods of food scarcity), locomotor patterns, microhabitat utilization, and/or timing of activities, promoting the long-term coexistence of species in local communities.1
Interspecific competition is thought to be highest among closely related taxa that occupy similar niche space and that competition is most intense when preferred resources are temporally or spatially scarce.2
Many primate species live sympatrically, sometimes coexisting with up to 10 or more other primate species, despite having similar body size and diet, making them a wonderful case study in which to understand niche partitioning.3
By examining the degree of resource partitioning among sympatric species, we may better be able to predict the species, and/or ecosystems, that are most susceptible to future risks of species extinction.4
Objective
Objective
Observe the foraging behavior, space use, and activity patterns of three closely related, large-bodied primates at the Tiputini Biodiversity Station in Amazonian Ecuador to better understand how these species are partitioning resources during periods of food scarcity.
Species of the study
Species of the study
These photos were taken by my field partner, Mary Lerch.
Wooly monkey
Lagothrix lagotricha poeppigii
Spider monkey
Ateles belzebuth
Howler monkey
Alouatta seniculus
Methods
Methods
Study Site: Tiputini Biodiversity Station, Ecuador (0° 38’ N, 76° 9’ W)
Data Collection: Direct observation: We followed four groups of woolly monkeys, two groups of howler monkeys, and two groups of spider monkeys with overlapping home ranges. On each day of observation, individuals from at least two different groups were followed simultaneously, with behavioral data collected through a combination of one-hour focal sampling and instantaneous scan sampling at 5-minute intervals. During scan samples, individual identity and/or age sex class was recorded, behavioral state, location, and height in the canopy of all conspecifics were recorded. If an individual was eating, the plant species, plant part, and phenophase were recorded. Biological samples of plant material (fruit, leaves, stems, etc) were collected and photographed for further analysis and identification.
Analyses: From the feeding bout data, we calculated the total time each primate species spent feeding on different fruits, types of leaves, and other plant material of different plant species, activity budgets, and ranging patterns.
Results
Results
Lagothrix was observed for 119.0 hours, Ateles for 99.92 hours, and Alouatta for 16.83 hours
Lagothrix was observed moving more than Ateles or Alouatta.
Ateles spent almost double the amount of time resting compared to Lagothrix and Alouatta spent almost three times as much resting.
Alouatta spent the majority of their days resting and less time feeding compared to Ateles and Lagothrix who spent almost ¼ of their day feeding.
Alouatta foraged on leaves and other plant material like stipules and stems more than the other two species.
Fruit made up 91.5% of Lagothrix diet, 95.2% of Ateles diet, and 78.5% of Alouatta diet
When feeding on fruits, Ateles and Alouatta primarily fed on Ficus, while Lagothrix primarily fed on Spondias. Ateles also consumed much more palm fruit (22.5%) with larger seeds (Oenocarpus and Iriartea) than the other two species.
Brosium was almost a quarter of Lagothrix fruit diet, but the other two species were not observed foraging on Brosium during this period.
Discussion
Discussion
The primates of TBS exhibit clear dietary and behavioral niche partitioning.
During this period of relative fruit scarcity, Alouatta and Ateles may be conserving energy by resting more, likely reflecting their specialization on foods such as leaves (Alouatta) and specific fruit types rich in lipids and with larger seeds (Ateles) that require longer digestion or less frequent foraging movements, respectively.
In contrast, Lagothrix likely employed an energy-maximizing strategy moving frequently and foraging for long periods of time on Spondias, Brosimum, and Ficus.5
All three species spent considerable time foraging on Ficus, which may serve as a fall back food given its asynchronous fruiting pattern allows for fruits to be available year-round.
The Alouatta groups we observed were not habituated, and therefore our observations of their activity and diet were limited and should be considered with caution.
Next Steps and Future Considerations
Next Steps and Future Considerations
Analyze the spatial data of each species to track for spatio-temporal overlap in activity and foraging patterns.
Conduct color analyses from photographs of the plant parts and fruits eaten by the primate species.
Collect more samples of Alouatta to have a more comparable dataset of behavioral observations with Ateles and Lagothrix.
References
References
Cardinale, B., Srivastava, D., Emmett Duffy, J. et al. Effects of biodiversity on the functioning of trophic groups and ecosystems. Nature 443, 989–992 (2006). https://doi.org/10.1038/nature05202.1, 2,4
Fiore, A. D., & Rodman, P. S. (2001). Time allocation patterns of lowland woolly monkeys (Lagothrix lagotricha poeppigii) in a neotropical terra firma forest. International Journal of Primatology, 22(3), 449–480.
https://doi.org/10.1023/a:1010759729567.5
Fleagle, J. G., C. H. Janson, and K. E. Reed (Eds.). 1999. Primate communities. Cambridge University Press, Cambridge, UK.3
Acknowledgments
Acknowledgments
Thanks to the Tiputini Biodiversity Station Management and Staff, the Ecuadorian government for permitting us to work in the Yasuní biosphere, and the many researchers, assistants, students, and sponsors that made this work possible. Special thanks to Santiago Villamil and Laura Jaimes for letting us use their spider monkey data and Anthony Di Fiore (UT-Austin) for mentorship and guidance. This research was supported by the Undergraduate Summer Scholars Program and Undergraduate Research Award at Miami University.
NACE Career Readiness Competencies
NACE Career Readiness Competencies
Through my research experience, I have gained career readiness skills such as communication, professionalism, teamwork, and technology. With this research experience being in a different country, I had the opportunity to communicate with people of different cultures and backgrounds from all over the world and learn about their research, personal lives, and interests. With this experience, I learned to always be prepared, complete my assigned tasks, demonstrate dependability, and show a high level of dedication to doing a good job in my role. I completed this research with a team of undergraduate students from Miami University, and I had help with data collection from other graduate students and research professors from other universities. We worked well together out in the field to collect our data, communicated with each other to know what our goals were for each day, employed personal strengths to complement those of others, built strong, positive working relationships, and held each other accountable for completing individual responsibilities. Also with this research experience, I had the opportunity to learn how to use a variety of different technologies, such as a hand-held GPS and a compass for navigation skills, radio telemetry to track the animal in the forest, and an online app on our phone to collect the data digitally.
Research Compliance Protocols
Research Compliance Protocols
All observers completed Miami's Institutional Animal Care and Use training and were certified to conduct observational research. Research was conducted in accordance with established ethical guidelines for observational study of wild primates and adhered to the American Society of Primatologists' Code of Best Practices in Field Primatology.
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