Parasitological studies of natural populations of neotropical primates are relatively rare, and few data were available previously for the red-handed howler monkey, Alouatta belzebul. In the present study, populations of A. belzebul were sampled at five sites in the area of the reservoir of the Tucuruí hydro-electric dam in southeastem Brazilian Amazonia, corresponding to the right bank of the Rio Tocantins. Sites included continuous forest and fragments of habitat on islands varying in area from 180 to 484 hectares. A primary aim of the study was the evaluation of the effects of habitat perturbation on patterns of infestation for endoparasites. Population density was estimated at each site using standard line transect surveys of 100-108 km per site. Fecal samples were collected from six to fourteen groups at each site, with a total of 40- 46 individual samples per site (n = 212). Samples were fixed in MIF (Mercury Chromed, Iodine and Formaldehyde), and observed under a 400x optic microscope. Population density varied between 66,4 and 191,5 individuals per square kilometer. Overall, 76,4% of the samples were positive for at least one species of endoparasite, and a total of thirteen species were identified, including eight species of heiminthes and five protozoans. Individual samples contained as many as five different species of endoparasites. At a given site, the number of species identified varied between seven and twelve, and infection rates between 67,5% and 86%. No systematic pattern of parasite diversity or infection rates was found in relation to variables such as population size or density, or habitat fragmentation. Diversity and infection rates varied as much between the two continuous forest sites as among the forest fragments, and were lowest overall at the site with the lowest population density. The only exception was Trypanoxyuris minutus, a common oxyurid transmitted through direct contact, for which a strong correlation was found between infection rates and population density. Overall, little evidence was found to support the hypothesis that habitat fragmentation has a systematic effect on infestation patterns in A. belzebul, although more detailed studies will be recommend before more definitive conclusions can be drawn.
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