This Biological Anthropology research was focused on the differential use of temporal long calls within four New World Monkey species (Ateles belzebuth, Lagothrix lagotricha poeppeiggi, Plecturocebus (Callicebus) discolor, and Alouatta seniculus) in the Amazon rainforest of Ecuador. This study analyzes the differences between species’ long calls to expand the information on why and more importantly when they are used, as well as what social structures impact these vocalizations. We used vocalization data collected opportunistically by observers between 2007 and 2018. For this study, we only analyzed vocalization records taken by observers that were in the field prior to sunrise, resulting in more than 800 vocalizations from the four species. On days in which multiple species vocalized, we used paired t-tests to determine if the timing of long calls were significantly different among species. As we predicted, Howler monkeys and Titi monkeys made calls significantly earlier in the morning than Spider monkeys or Woolly monkeys, and no significant differences were found in the timing of calls between Howler and Titi monkeys, nor Spider and Woolly monkeys. Although Titi monkeys often vocalized before sunrise, an interesting pattern emerged in which some of their first calls were not produced until 2 hours after sunrise. Many of these later long calls were likely instigated by intergroup encounters, but may also reflect weather patterns or a thermoregulatory constraint experienced by these small-bodied primates. Future investigations will include how environmental factors such as rainfall, temperature, and humidity influence call production. This experience is valuable to its researchers as they all hope to go into animal based career fields where the analysis of animal behavior will be a necessary and beneficial tool.
Authors: Katelyn McCoy, Gillian Mescher, Abigail Sheely
Faculty Advisors: Kelsey Ellis and Max Snodderly, Department of Anthropology
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