Edge effects on scale-dependent density patterns in two sympatric mouse lemurs in northwestern Madagascar

Edge effects result from the penetration of abiotic and biotic conditions in the non-forest matrix into the forest interior. Rampant forest loss and fragmentation has resulted in 70% of the world’s forests being within 1 km of a forest edge. Thus, edge effects are a dominant feature of most forest habitats. However, there are few empirical data on inter-site differences in edge responses in primates and none in lemurs. We used Spatially Explicit Capture-Recapture (SECR) models to determine density patterns for two species of sympatric mouse lemurs (Microcebus murinus and M. ravelobensis) in two forest landscapes in northwestern Madagascar. The goal of our study was to determine if mouse lemurs displayed spatially variable responses to edge effects at varying landscape scales. We trapped 126 M. murinus and 79 M. ravelobensis at the Mariarano Classified Forest (MCF) and 78 M. murinus and 308 M. ravelobensis in the Ambanjabe Forest Fragment Site (AFFS). At regional and landscape-specific scales, SECR models estimated different density patterns between both species as a result of variation in edge distance. M. ravelobensis had negative density responses to edge habitats whereas M. murinus generally had positive or neutral density responses to edge habitats. The spatial variability of our results using SECR models indicate the importance of studying the population ecology of primates at scales that are appropriate to the processes of interest.