Shifting Biogeographic Patterns of Microcebus ravelobensis and M. murinus

It is important to understand how sympatric congeners can co-occur within the same landscapes to better understand niche differentiation and how each species respond to habitat modification. We compiled previously published, long-term data from several studies on encounter rates of two sympatric mouse lemurs ( Microcebus ravelobensis and M. murinus ) in different survey sites (surveyed portions of continuous forest and individual fragments) using trapping (N = 16 sites; 42 samples) and visual (N = 42 sites; 73 samples) survey methods in Ankarafantsika National Park, Madagascar (total N = 58 sites; 115 samples). A sample reflects multiple surveys, visual, and/or trapping (N = 2–21) along a line-transect and/or trapline within 1 year. We found higher encounter rates of M. ravelobensis and M. murinus in continuous forests and fragmented forests, respectively. Contrary to studies conducted at a smaller scale, yearly encounter rates for M. ravelobensis were negatively associated with rainfall but were positively associated with rainfall for M. murinus . Like previous studies, we found a negative correlation in encounter rates between M. ravelobensis and M. murinus in continuous forests. However, in fragmented forests there was a significant positive relationship between the two species . Our data suggest that M. ravelobensis preferred continuous forest habitat, whereas the congeneric M. murinus preferred fragmented forest habitat. Such results are likely related to species-specific ecological requirements: whereas the continuous forest has conditions that M. ravelobensis finds preferential (i.e., wetter, taller, and denser forests), the forest fragments are drier, habitat that is preferred by M. murinus.