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Abstract of Monkey Research Findings


We studied the home range size of Alouatta palliata during the wet season and how it was affected by human encroachment, such as crop fields, on the Isle de Ometepe in Nicaragua. A specific group of 13 individuals was chosen to be studied on the southeast side of the Maderas Volcano. A specific individual was chosen and followed daily anywhere from 3-7 hours each day for a total of 144 hours during a 3 week period. Each tree, where they were seen, was tagged and the total home range size was determined to be 8.75 hectares. The average home range size is 10-60 hectares. Much of their home range was bordered by crop fields. They were observed on two or three sides on several crop fields, leading the researchers to infer that the crop fields indeed diminished home range size and interfered with daily ranging behavior by causing the primates to move around the crop fields. Because A. palliata is mainly a folivore with a relatively low BMR, such movement to go around crop fields causes it to expend much needed energy unnecessarily. Adding this to the fact that other howler groups and disturbed area bordered the only areas where there were no crop fields, this specific group was basically fenced in. Having a territory that has no potential to expand is detrimental to this group in that they are restricted to the resources in their current range and cannot exploit any other sources of food.