Do Patch Size and Interpatch Distance Influence the Distribution of Brown Howler Monkeys (Alouatta guariba clamitans) in a Fragmented Landscape in South Brazil?

Abstract

The theories of island biogeography, metapopulation, and landscape ecology have been applied to study the influence of habitat loss, patch size, spatial isolation, and dispersal ability on species survival in fragmented landscapes. Here we test whether forest fragment size, distance to the nearest patch, and distance to the nearest potential mainland are good predictors of the presence of brown howler monkeys (Alouatta guariba clamitans) in fragments immersed in a matrix dominated by ranching, farming, and eucalyptus forestry in south Brazil. We also infer to which model of metapopulation (classical, mainland–island/source–sink, patchy, and nonequilibrium) the set of howler monkey populations best fit. From March 2003 to July 2005, we conducted censuses on 63 forest fragments and sighted brown howlers in 28 (occupancy index = 44 %). Fragment size (0.5–992 ha), distance to the nearest potential mainland (61–13,460 m), and distance to the nearest fragment (47–13,460 m) did not predict the presence of howler monkeys in these forest remnants. We conclude that the absence of brown howlers in many forest patches and the lack of relationship between their presence and fragment size and interpatch distances suggest that the set of populations in the study region best fits a nonequilibrium metapopulation model.