Edge effects in the primate community of the biological dynamics of Forest Fragments Project, Amazonas, Brazil.

While much is known about abiotic and vegetative edge effects in tropical forests, considerably less is known about the impact of forest edges on large mammals. In this study, we examine edge effects in a primate community to determine: 1) the distance from the edge over which edge effects in primate density are detectable, 2) whether individual species exhibit edge effects in their density, and 3) whether biological characteristics can be used to predict primate presence in edge habitats. Given their importance to many primate species, we also examine the influence of the number of large trees. We found edge penetration distances of 150 m for the five species that experienced edge effects, suggesting that primates respond to edge-related changes in the plant community that are known to be strongest over the first 150 m. Four species had higher edge densities: Alouatta macconnelli (folivore-frugivore), Chiropotes chiropotes (frugivorous seed predator), Saguinus midas (frugivore-faunivore), and Sapajus apella apella (frugivore-faunivore); one species' density was lower: Ateles paniscus (frugivore); and the final species, Pithecia chrysocephala (frugivorous seed predator), did not show an edge-related pattern. The lone significant relationship between the biological characteristics examined (body weight, diet, group size, and home range size) and primate presence in edge habitats was a negative relationship with the amount of fruit consumed. Though we did not examine primate responses to edges that border a denuded matrix, we have shown that edges influence primate distribution even following decades of secondary forest regeneration at habitat edges.

The effects of observer presence on the behavior of Cebus capucinus in Costa Rica.

We report on the responses of Cebus capucinus in the Santa Rosa Sector of the Area de Conservación Guanacaste, Costa Rica, to the presence of observers over a 4-week period. Study groups were habituated to different degrees: (1) Cerco de Piedra (CP): continuous observations began in 1984; (2) Exclosure (EX): focus of an 18-month study on males from 1998 to 1999; and (3) NBH: never studied/followed but the group frequently encounters researchers. We collected three types of data: group scans (group state was coded as calm or agitated at observer presence), focal animal data (observer-directed behaviors were recorded), and fecal cortisol levels. The two less-habituated groups (NBH and EX) differed significantly from the habituated group (CP) in their behavioral and cortisol responses, and they showed an increase in habituation over the study period (agitation and cortisol levels both dropped). Individuals in NBH also decreased their responses to observers during focal follows; however, at the end of the study the responses of the two less-habituated groups (NBH and EX) remained elevated in comparison to the habituated group (CP), suggesting the need for further habituation. Unlike capuchin groups that rarely encounter humans, NBH and EX never fled from observers and they rarely emitted observer-directed alarm calls. We suggest that the permanence of habituation and the ability to habituate animals passively through a neutral human presence are both important considerations for researchers conducting studies in areas where animal safety from poachers, etc. cannot be guaranteed.