A biogeographical perspective on the variation in mouse lemur density throughout Madagascar

Abstract

Madagascar is home to the smallest primates in the world, the mouse lemurs (Microcebus species). Twenty‐four species of mouse lemur are currently recognised and are found in variable ecosystems, from dry forests and spiny deserts to humid forests. Due to their widespread distribution and the large number of sympatric species, mouse lemurs can be used as a model to understand the linkages among species richness, population density, and habitat. As all lemurs are threatened by habitat loss and fragmentation, this information can also be used to inform conservation management. We hypothesise that on an island‐wide scale, we will find higher population densities in western dry forests than in eastern humid forests because the western dry forests exhibit lower species richness, more sympatric habitat use, and lower resource stability than the eastern humid forests. We conducted a literature review of population density estimates of known mouse lemur species, and used those data to conduct a meta‐analysis and estimate overall average population density by geographic region. Our findings suggest that mouse lemur species living in western dry forest generally exhibit higher densities than those in eastern humid forests. This may be partly explained by higher habitat fragmentation in western dry forests, where species co‐occur, but is likely to be a function of the magnitude and variability in seasonally available resources in each forest type. Higher seasonality results in less constant food availability and lower levels of environmental predictability, fostering species capable of coping with environmental change and maintaining high densities throughout periods of resource paucity. Our study highlights the importance of conducting Microcebus population density research that adheres to standardised methodological approaches. We point to the need for population density estimates for several species for which data are lacking. Such knowledge is important to assess the conservation status of these species, but also to enhance our ability to identify the macro‐biogeographical and local ecological drivers of interspecific and intraspecific variability in population density.

Mouse lemurs’ and degraded habitat

“…Home to ca. 110 currently recognized lemur taxa (Louis Jr. & Lei, 2016; Mittermeier et al, 2014; Setash, Zohdy, Gerber, & Karanewsky, 2017), Madagascar harbors the second-highest primate diversity of all countries and the highest proportion of primate endemism (Mittermeier et al, 2010). Mouse lemur habitats and population sizes are decreasing, while their level of threat is rising, mainly from deforestation, forest degradation, and poaching (IUCN, 2017; Schwitzer et al, 2013; Schwitzer, Mittermeier, et al, 2014).…”

“…Dry and humid forest species typically have a different diet (Kappeler & Rasoloarison, 2003; Radespiel, 2007), and dry forests generally harbor higher population densities than humid forests (Randrianambinina et al, 2010; Setash et al, 2017). In addition, western dry and eastern humid regions harbor contrasting climatic conditions and climatic extremes that may have led to the development of independent unique resource use strategies (Génin, 2008, 2010; Kobbe & Dausmann, 2009).…”

Pedigree-based measurement of thede novomutation rate in the gray mouse lemur reveals a high mutation rate, few mutations in CpG sites, and a weak sex bias

“…Mouse lemurs comprise a radiation of morphologically cryptic primates distributed throughout Madagascar (Hotaling et al, 2016). Numerous studies have suggested that their rapid speciation dynamics may reflect climatic change through time in Madagascar (Andriatsitohaina et al, 2020;Setash et al, 2017) and that their unique life history characteristics make them an ideal genetic model organism (Ezran et al, 2017;Hozer et al, 2019). Thus, an accurate mutation rate estimate for these organisms can potentially yield valuable insight into both geological and biological phenomena.…”

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

“…It is, therefore, important to investigate these responses (e.g. through population density estimates) across several species to identify macro-biogeographical and local ecological drivers of inter-and intraspecific variability in response to habitat (Setash et al 2017). 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).…”