Occurrence of lemurs in landscapes and their species‐specific scale responses to habitat loss

Abstract

Studies on the impact of habitat loss on species occurrence consistently find that the amount of habitat (measured as patch area) is a major determinant of species occurrence at a patch-level. However, patch-level research may fail to detect important patterns and processes only observable at a landscape-level. A landscapelevel approach that incorporates species-specific scale responses is needed to better understand what drives species occurrence. Our aim was to determine the landscape-level scale of effect of habitat amount on the occurrence of three species of nocturnal lemurs (Cheirogaleus medius, Microcebus murinus, and M. ravelobensis).We surveyed line transects to determine the occurrence of three lemur species within a fragmented landscape of deciduous dry forest and anthropogenic grassland in northwestern Madagascar. To determine the scale of effect of habitat loss on lemur occurrence, we compared logistic regression models of occurrence against habitat amount among eight different landscape scales using Akaike's Information Criterion values. We found differing scale responses among the lemurs in our study.Occurrence of C. medius responded to habitat amount at scales between 0.5-4 ha, M. murinus at scales between 1 and 4 ha and M. ravelobensis at scales between 0.125 and 4 ha. We suggest that the scale of effect for C. medius is mediated by their ability to hibernate. A relatively lower scale-response for Microcebus spp. likely reflect their omnivorous diet, small habitat requirements, and limited dispersal ability. Differences in scale responses between M. murinus and M. ravelobensis are likely a result of differing dispersal ability and responses to edge effects between these species. Our study is among the first on lemurs to show the value of a landscape-level approach when assessing the effects of habitat loss on species occurrence. K E Y W O R D S arboreal, biogeography, fragments, Madagascar, primate

Environmental drivers of Cheirogaleidae population density: Remarkable resilience of Madagascar’s smallest lemurs to habitat degradation

“…For instance, lemur population density has been observed to vary greatly between Madagascar's various forest types (Axel & Maurer, 2011), with some studies revealing higher populations in the dry forests of western regions than in the humid forests of the east (Ganzhorn et al, 2006;Setash et al, 2017), and higher densities in forest interior habitat than in forest edges (Lehman et al, 2006a). Habitat degradation and disturbance have also been demonstrated to have mostly negative effects on the population density of lemurs (Ganzhorn et al, 1997;Lehman et al, 2006a), and the population responses to these anthropogenic drivers are often reported as species-specific (Eppley et al, 2020;Herrera et al, 2011;Lehman et al, 2006b;Steffens et al, 2020). High population density variation has been observed along several environmental gradients, and there is evidence of both positive and negative correlations between lemur density and elevation (Campera et al, 2020;Goodman & Ganzhorn, 2004) and negative correlations with water availability (Axel & Maurer, 2011).…”

Population Dynamics of Nocturnal Lemurs in Littoral Forest Fragments: The Importance of Long-Term Monitoring

“…obs.). These plantations likely provide a highly abundant and nutritious resource as the lemurs emerge from hibernation and although G. robusta can become invasive, capitalising on such resources could provide an additional management tool in future conservation efforts (Ganzhorn et al 1991;Donati et al 2020;Steffens 2020;Konersmann et al 2021).…”

“…body size, diet, habitat requirements) and habitat characteristics (e.g. fragment size, connectivity, level of anthropogenic disturbance and resource patchiness) as important predictors for primate survival in fragmented landscapes (Isaac and Cowlishaw 2004;Eppley et al 2020;Steffens et al 2020). However, the specific nature and relevance of local conditions underscores the importance of documenting species-and population-specific responses (Steffens et al 2020).…”

Ground‐based vegetation descriptions and remote sensing as complementary methods describing habitat requirements of a frugivorous primate in northern Madagascar: implications for forest restoration

“…Also, other lemur species' diversity, abundance and habitat use are positively correlated to plant productivity (Hudson, 2011; Herrera, 2017; Campera et al ., 2020). On the other hand, the results might come about by different temporal or spatial scales of analysis which may or may not reflect the scale of effect perceived by an animal at a given time (Lahoz‐Monfort et al ., 2010; Jackson & Fahrig, 2012; Moraga et al ., 2019; Steffens et al ., 2020).…”

“…Generally, investigating the response of a certain species to a certain landscape variable critically depends on choosing an appropriate scale, called the scale of effect (Jackson & Fahrig, 2012; Moraga, Martin, & Fahrig, 2019). There are also cases where it was possible to describe habitat suitability for lemurs on relatively large scales, using habitat characteristics such as plant productivity or water/forest occurrence assessed by remote sensing methods (Irwin, Johnson, & Wright, 2005; Lahoz‐Monfort et al ., 2010; Mercado Malabet et al ., 2020; Steffens, Mercado Malabet, & Lehman, 2020).…”