Seasonal variation in the distribution patterns of lemurs reveals different proximity patterns to forest habitat edge zones in South-Eastern Madagascar

Background/Question/Methods

In forest landscapes, edge effects are caused by the penetration of biotic and abiotic conditions from the non-forest matrix into the forest interior. Edge effects are particularly relevant to studies of lemur conservation biogeography due to the high levels of forest loss and fragmentation on Madagascar. Patterns of climatic seasonality are also important to the study of lemur conservation, as these have influenced many aspects of lemur evolutionary ecology (e.g., diet and ranging patterns). Although lemurs are strongly influenced by seasonality and edge habitats are an increasingly dominant feature of their forest habitats, there are few data on whether or not any species exhibit seasonal responses to edge effects. In this study, we evaluated for the first time whether four lemur species (Avahi peyrierasi, Eulemur rubriventer, Hapalemur griseus ranomafanensis, and Microcebus sp.) exhibited seasonal variations in their edge proximities in SE Madagascar. We conducted diurnal (N = 348) and nocturnal (N = 134) lemur surveys along six 1,250m transects over 3 years in the Vohibola III Classified Forest. We then compared variation in edge proximity for these four species. This involved comparison of their distributions along the forest profile between the warm-wet and cool-dry seasons seasonal periods in this region.

Results/Conclusions

The four lemur species exhibited considerable interspecific differences in the overall distribution and shape of their edge proximities patterns between seasons. A. peyrierasi aggregated significantly further away from the forest edge during the warm, wet season than during the cool, dry season. The combination of a highly selected diet in A. peyrierasi and anthropogenic depletion of their preferred food and sleeping trees in edge habitats may explain seasonal changes in edge proximity. The lack of a significant difference in seasonal edge effect in the other three lemur species likely reflects their ecological flexibility. In H. g. ranomafanensis and E. rubriventer, active defense of home ranges and territories may limit the amount of observed seasonal variation. Further research is needed to better understand this newly described pattern of seasonal variations in edge responses in lemurs.