Assessing habitat utilization by neotropical primates: a new approach.

This study aims to ascertain habitat utilization, in relation to forest structural variation, by a multi-species group of primates in tropical lowland rainforest in Southeast Peru during dry season. A new approach to assessing habitat utilization was used. Habitat variation was described by structural and indicator variables collected in quadrats along transects through a study area within Terra Firme and Floodplain forest. Variables were grouped into 'factors' accounting for most of the variation by means of a Principal Components Analysis (PCA). Presence or absence of the primates within the quadrats, assessed by repeat transect surveys, was taken to indicate habitat preferences. Discrimination between the habitat and forest structure in areas of primate presence as opposed to absence was carried out by means of Discriminant Function Analysis (DFA). This highlighted patterns in most utilized habitat. Vertical utilization of the forest was also assessed along with presence in bamboo and general activity on encounter. Suggestions of habitat preference and utilization are made for each of the six sympatric species studied, based on significantly discriminating habitat factors, vertical stratification on encounter and relationships with bamboo. Saguinus fuscicollis and Cebus moloch appeared as habitat generalists. Cebus apella, Saimiri sciureus, and Aotus spp., exhibited varying degrees of preference for habitat factors suggesting disturbed forest, Cebus albifrons was more generalistic but with a possible association with primary, naturally disturbed forest. C. apella was encountered in Terra Firme forest significantly more than in Floodplain. For S. sciureus, C. moloch, and C. apella, upper understory was the most utilized forest layer, for C. albifrons, middle canopy and for S. sciureus and Aotus spp., lower understory. Both positive and negative relationships with bamboo were highlighted. Significant positive relationships between Aotus spp., and bamboo suggest dense bamboo stands provide important daytime resting sites for this nocturnal species. C. moloch was also shown to utilize bamboo whereas S. fuscicollis appeared to actively avoid it. High levels of conformity with past studies in terms of habitat utilization patterns described for the species studied supports the conclusion that the methods used in this study provide an effective means of assessing primate habitat utilization within complex habitat.