Being the largest New World monkeys, mantled howler monkeys (Alouatta palliata) and spider monkeys (Ateles geoffroyi) vary greatly in terms of appearance, diet, and time budgets. Recent studies show that Alouatta palliata spends about 17% of their time foraging and about 80% of their time in a resting activity. Conversely, Ateles geoffroyi have been shown to budget their time as such: 33.5% foraging, 24.1% resting, 32.6% travelling, and the rest of the time is divided between other categories. This difference in time budgeting is attributed to the difference in diets between species, as Alouatta palliata has a folivorous diet and Ateles geoffroyi has a frugivorous diet. Because fruits are not located in any specific area, but are spread out throughout the forest, there is a general trend of frugivores spending more time looking for food, while folivores spend more time resting to digest food. When comparing similarities between species, simultaneous study of activity budgets between co-existing species is rare. Additionally, activity budgets of Alouatta palliata and Ateles geoffroyi at the La Selva Research Station are unknown. The question then becomes: do these different species attribute their time at the La Selva Research Station similarly? I hypothesize that Alouatta palliata will have more resting and foraging periods compared to Ateles geoffroyi. I will be going to the La Selva Research Station, located in Costa Rica, in May 2022. The La Selva Research Station offers 1,600 hectares of forest where a number of Alouatta palliata and Ateles geoffroyi can be found. Alouatta palliata have fur that ranges from walnut, gold, chocolate brown, and black colors across their bodies; whereas Ateles geoffroyi are reddish brown, yellowish brown, black, or silvery-gray. Weight differences of Alouatta palliata and Ateles geoffroyi are important, too. Alouatta palliata males weigh between 4.5 kg and 9 kg with females weighing 3.1 kg to 7.6 kg. Ateles geoffroyi males, on the other hand, weigh between 7.4 kg and 9 kg, and females weigh between 6 kg and 9.4 kg. Instantaneous focal sampling will be completed at 1-minute intervals. Key characteristics that are going to be observed are feeding, aggression, vocal calling, resting, and travel. This allows a broad enough spectrum that multiple data points are going to be collected for a quantitative analysis. This is completed by comparing the proportion of budget categories observed, by species, relative to the number of scans obtained. These budgeting categories will then be compared to those from other sites.
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