Distribution of the black howler monkey (<i>Alouatta pigra</i>) and the mantled howler monkey (<i>A. palliata</i>) in their contact zone in eastern Guatemala

Abstract

We studied the geographic distribution of the endangered black howler monkey, Alouatta pigra, in its southeastern range in eastern Guatemala along its putative contact zone with the mantled howler monkey, A. palliata. A distributional survey of both species was conducted through direct observations and interviews, and the data analyzed with GIS to detect potentially limiting geographic and ecological factors. Alouatta pigra was not associated with any specific vegetation type or altitudinal range, as it occurred in many forest types from the lowlands up to elevations of 2705 m a.s.l., in contrast to prior reports of it being restricted to elevations below 400 m a.s.l. and having a strong affinity for riverine forests. Alouatta palliata did not occur at the higher elevations. Distribution of both howler monkey species was unaffected by the presence of Ateles, by protection status of the survey site, or by hunting activities. Deforestation appears to have restricted both species in some areas. Throughout the southeastern range of A. pigra, we found no evidence for current sympatry with A. palliata, as their distributions are separated by a river barrier and unsuitable dry shrubland. Ecological preferences also seem to reinforce allopatry, with only A. pigra occurring in wet and cold montane forests of the Sierra de las Minas. Our data indicate that highland habitats in Mexico and Guatemala, previously considered unsuitable for A. pigra, may need to be evaluated for distribution assessments and management plans. Populations of A. pigra in the diverse protected ecosystems in eastern Guatemala may be an important component for conservation of the species.