Demography, life history and migrations in a Mexican mantled howler group in a rainforest fragment.

This paper represents the results of a long-term study (1996-2003) on the demographic changes over time of a Mexican mantled howler (Alouatta palliata mexicana) group in a rainforest fragment (40 ha) in Los Tuxtlas, Mexico, with a follow-up census 3 years later (2006). In addition to demographic and life history parameters, we describe six dispersal events. Our results suggest that this group has been expanding during the study period, growing from six to 12 individuals, with an annual average intrinsic growth rate of 0.07, an infant survivorship of 67%, and an average immature to female ratio of 0.90. This increase in size is probably related to the high food availability in their home range. However, fragment isolation may be negatively affecting the dispersal patterns typical of the species, which could result in a loss of genetic variability over time.