I conducted a comparative study in north-central Belize on the ecological effects of Alouatta pigra in several semi-deciduous forest fragments to test hypotheses concerning the relationship between diet and home range to sapling establishment and understory regeneration. Howler monkeys persist in small forest fragments when other large frugivores do not, and consequently, become dominant dispersers of large-seeded plants.

To test this, quantitative behavioral data were collected for 12 months between 1994-1996 at the Community Baboon Sanctuary on primate feeding ecology in black howler troops living within six distinct forest fragments ranging from 1.25 to >100 ha. Vegetation transects were conducted within primate home ranges to compare seedling/sapling distribution of the most utilized fruit species. An additional control site without howlers was sampled with vegetation transects. Soil samples were collected in all sites to determine basic chemical composition.

In general, diets were selected non-randomly; relatively few plant species made up a large proportion of the diets; Ficus in particular was the most important food species; and when fig fruits were available, they greatly influenced the rest of the howler diet. Based on fruit species the monkeys consumed, howlers are good seed dispersers, but their effectiveness is influenced by other site-specific environmental conditions (e.g., fragments size, rate of past and present anthropogenic disturbance, soil composition) in fragments which negatively affect recruitment for a number of howler-dispersed tree species. However, howlers had a positive effect on sapling recruitment when compared to the site without primates, indicating that howler seed dispersal is important in general to fragmented forests within the Community Baboon Sanctuary.

Based on my findings, I caution conservation professionals working in highly disturbed, fragmented habitats to be aware that saving a habitat for a single species may not be effective without holistic approaches which protect species interactions and ecological processes.