Responses to deforestation in a group of mantled howlers (Alouatta palliata) in Costa Rica

To evaluate the effects of partial deforestation of the home range of a group of free-ranging howlers on Hacienda La Pacifica, Costa Rica, we compared activity patterns, social interactions, daily travel lengths, group sizes and migration patterns before, during, and after habitat destruction. Immediate responses were a decrease in social interactions and increase in start to travel. Long-term responses included an increase in feeding time and longer daily path length. The long-term responses were associated with the adjustment to a new home range which was longer and narrower, with the patchiest resources at the furthest end points. Group size decreased due to a significant decrease in adult males and females and a significant increase in infant deaths between the predeforestation period and the deforestation/postdeforestation periods. Significant increase in adult female deaths/emigration continues, though emigration of immatures remains unchanged. Reduced group size could be due to reduced resources or disturbed migration routes throughout the farm due to the construction of a major canal system.