Rossi de Leon
Howler monkeys (Alouatta spp.) are known for their adaptability, allowing them to inhabit a large range of forest types and driving high levels of variation in ranging and behavioral patterns. I address a series of hypotheses relating these relationships: 1) If an energy minimizing lifestyle is an adaptation to eating high quantities of leaves, then howler groups that have a high proportion of leaves in their diet will occupy smaller home ranges, have shorter daily path lengths, and spend more time resting, 2) if temperature is the primary driver of high levels of resting, then howlers will conserve energy and rest more at lower temperatures, 3) home range and daily path length will increase with group size. To test these hypotheses, I studied the ranging and behavioral patterns of two groups of Black and Gold Howler monkeys (Alouatta caraya) inhabiting a gallery forest in Formosa, Argentina. I followed each group from sunrise to sunset for a total of six days each. Compared to other studies, the groups had the smallest home ranges for Alouatta (1.23 ha and 0.92 ha). Both groups followed expected activity patterns, sleeping for roughly 60% of the day and eating primarily leaves supplemented by small amounts of fruit and flowers. Higher leaf consumption was correlated with increased resting time, but not smaller home range or shorter daily path lengths. Contrary to expectations, there appeared to be a very slight positive correlation between temperature and percent resting. Finally, home range and daily path length did not increase with group size. These data give us insight into the species’ adaptability since this population is found at the extreme southern edge of where howlers are found.