The effect of habitat disturbance on the abundance of nocturnal lemur species on the Masoala Peninsula, northeastern Madagascar

Abstract

Madagascar is one of the world's biodiversity hotspots. The island's past and current rates of deforestation and habitat disturbance threaten its plethora of endemic biodiversity. On Madagascar, tavy (slash and burn agriculture), land conversion for rice cultivation, illegal hardwood logging and bushmeat hunting are the major contributors to habitat disturbance. Understanding species-specific responses to habitat disturbance across different habitat types is crucial when designing conservation strategies. We surveyed three nocturnal lemur species in four forest types of varying habitat disturbance on the Masoala Peninsula, northeastern Madagascar. We present here updated abundance and density estimates for the Endangered Avahi mooreorum and Lepilemur scottorum, and Microcebus sp. Distance sampling surveys were conducted on 11 transects, covering a total of 33 km after repeated transect walks. We collected data on tree height, bole height, diameter at breast height, canopy cover and tree density using point-quarter sampling to characterise the four forest types (primary lowland, primary littoral, selectively logged and agricultural mosaic). Median encounter rates by forest type ranged from 1 to 1.5 individuals (ind.)/km (Microcebus sp.), 0-1 ind./km (A. mooreorum) and 0-1 ind./km (L. scottorum). Species density estimates were calculated at 232.31 ind./km (Microcebus sp.) and 121.21 ind./km (A. mooreorum), while no density estimate is provided for L. scottorum due to a small sample size. Microcebus sp. was most tolerant to habitat disturbance, exhibiting no significant effect of forest type on abundance. Its small body size, omnivorous diet and generalised locomotion appear to allow it to tolerate a variety of habitat disturbance. Both A. mooreorum and L. scottorum showed significant effects of forest type on their respective abundance. This study suggests that the specialist locomotion and diet of A. mooreorum and L. scottorum make them susceptible to the effects of increasing habitat disturbance.

Forest Type Influences Population Densities of Nocturnal Lemurs in Manompana, Northeastern Madagascar

“…We found higher densities of a folivorous and an omnivorous lemur in regenerating secondary forest than in mature forest in the Manompana region of north-eastern Madagascar. However, consistent with other research we recorded higher lemur species diversity in mature forest (Irwin et al 2010;Sawyer et al 2017;Schwitzer et al 2011). The results highlight the importance of regenerating secondary forest as a viable habitat for the eastern woolly lemur and mouse lemur.…”

“…Low-intensity selective logging or low-intensity bush-fallow agriculture can open up a habitat allowing increased levels of light penetration, which may have a positive effect on forest productivity and/or increased leaf quality (Ganzhorn 1995;Ganzhorn et al 1997;Oates 1996;Onderdonk and Chapman 2000;Skorupa 1986). Nocturnal lemurs are often largely tolerant of disturbed habitat, but diet can be a determining factor in their success (Lehman et al 2006a;Lehman et al 2006b;Randrianambinina et al 2010;Sawyer et al 2017). Some folivorous lemurs respond positively to low-medium levels of forest disturbance such as the Southern lesser bamboo lemur (Hapalemur meridionalis) which tolerated significant levels of habitat degradation by using an invasive species habitat for feeding and resting (Eppley et al 2015).…”

“…The folivorous nocturnal lemurs (Avahi sp., and Lepilemur sp.) have shown mixed responses to disturbed habitat (Ganzhorn 1987;Norscia 2008;Sawyer et al 2017). The folivorous Avahi mooreorum and Lepilemur scotorum were more susceptible to increasing habitat disturbance (Sawyer et al 2017), and Lepilemur grewcockorum was less abundant in degraded forest, most likely due to the reduced availability of tree holes in oldgrowth trees (Randrianambinina et al 2010).…”

“…have shown mixed responses to disturbed habitat (Ganzhorn 1987;Norscia 2008;Sawyer et al 2017). The folivorous Avahi mooreorum and Lepilemur scotorum were more susceptible to increasing habitat disturbance (Sawyer et al 2017), and Lepilemur grewcockorum was less abundant in degraded forest, most likely due to the reduced availability of tree holes in oldgrowth trees (Randrianambinina et al 2010). Omnivorous or insectivorous lemurs are often more abundant in disturbed habitats than in mature forests, potentially due to an increased light penetration and understory biomass linked with high insect abundances (Andriamandimbiarisoa et al 2015;Corbin and Schmid 1995;Herrera et al 2011).…”

Lemurs on a sinking raft? : The ballast of anthropogenic disturbances

“…In West Kalimantan, logged areas had fewer large food trees and a greater number of canopy gaps, leading to reduced orangutan (Pongo pygmaeus) nests (Felton et al, 2003). Furthermore, nocturnal lemur encounter rates were higher in primary compared to disturbed forests (Sawyer et al, 2017). In contrast, Javan slow lorises (Nycticebus javanicus) showed high abundances in agricultural mosaic habitats (Rode-Margono et al, 2014).…”