Population density of Ecuadorian mantled howler monkeys (Alouatta palliata aequatorialis) in a tropical dry forest, with information on habitat selection, calling behavior and cluster sizes

The Ecuadorian mantled howler monkey (Alouatta palliata aequatorialis) is classified vulnerable due to habitat loss and hunting, yet little is known about the subspecies in the southern part of its range, and previous studies have been conducted in humid forests. Here we present the first data on Ecuadorian mantled howler monkeys in Cerro Blanco Protected Forest, a large fragment of tropical dry forest near Guayaquil Ecuador in the south of the subspecies range. The protected forest is a mosaic of old forest, recovering secondary forest and areas restored by planting native tree species. We used a triangulation survey to locate howler monkeys by their calls and assess habitat selection and population density. Although we found a diurnal pattern in calling behavior, with increased loud calls heard during midday, no temporal pattern was found in the number of calls triangulated. Mean cluster sizes of Ecuadorian mantled howler monkeys in Cerro Blanco Protected Forest are smaller than those observed for A. palliata at other sites. We calculated an overall density of 7.71 (95% CI: 4.08–14.19) clusters per km2, which equates to 47 individuals per km2 (95% CI: 25–87 individuals). Ecuadorian mantled howler monkeys did not appear to select or avoid any of the habitat characteristics measured, which is encouraging as we found no evidence clusters were avoiding regenerating or replanted areas.