Daily and Seasonal Patterns of Roaring and Spacing in Four Red Howler Alouatta seniculus Troops

Daytime and seasonal patterns of roaring and spacing are described for the red howler monkey, Alouatta seniculus. A seasonal difference in howling at midday during the dry season is correlated with high temperature and high insolation. Interacting troops come closer to each other and roar more during the dry season, when they often meet around fruiting figs, than during the wet season. It is suggested that during the dry season food is more patchily distributed, which results in more intense competition between the groups. Smaller or lower quality food patches may be available to A. seniculus than to A. palliata of Central America. The limited data support the hypothesis that howlers minimize the costs of travel by forming smaller troops when smaller or lower quality food patches are available.