Lemur responses to edge effects in the Vohibola III classified forest, Madagascar

Abstract

Forest edges are dynamic zones characterized by the penetration (to varying depths and intensities) of conditions from the surrounding environment (matrix) into the forest interior. Although edge effects influence many tropical organisms, they have not been studied directly in primates. Edge effects are particularly relevant to lemurs because of the highly fragmented forest landscapes found in Madagascar. In this study, data are presented regarding how the densities of six lemur species (Avahi laniger, Cheirogaleus major, Eulemur rubriventer, Hapalemur griseus griseus, Microcebus rufus, and Propithecus diadema edwardsi) varied between six 500-m interior transects and six 500-m edge transects in the Vohibola III Classified Forest in SE Madagascar. Diurnal (n = 433) and nocturnal (n = 128) lemur surveys were conducted during June-October 2003 and May-November 2004. A. laniger, E. rubriventer, and H. g. griseus exhibited a neutral edge response (no differences in densities between habitats). M. rufus and P. d. edwardsi had a positive edge response (higher densities in edge habitats), which may be related to edge-related variations in food abundance and quality. Positive edge responses by M. rufus and P. d. edwardsi may ultimately be detrimental due to edge-related anthropogenic factors (e.g., hunting by local people). The negative edge response exhibited by C. major (lower densities in edge habitats) may result from heightened ambient temperatures that inhibit torpor in edge habitats.

Travel and Spatial Patterns Change When Chiropotes satanas chiropotes Inhabit Forest Fragments

“…In other studies, fragment size does not predict a primate's activity budget and ecology (Bicca-Marques 2003;Cristóbal-Azkarate and ArroyoRodríguez 2007), group size does not predict home range size (Bicca-Marques 2003), group size is not associated with fragment size (Umapathy and Kumar 2003), and density is not greater in forest fragments (Wong and Sicotte 2007). Such variability in results illustrates the ecological complexities in forest fragmentation research, as variables such as fragment size (Harcourt and Doherty 2005;Wieczkowski 2004), matrix composition (Anderson et al 2007), edge effects (Lehman et al 2006;Mbora and Meikle 2004), predation (Tutin 1999), and seasonality of resources (Martins and Setz 2000) may affect species presence, distribution, and behavior. Further, the lack of clear patterns predicting species' responses to forest fragmentation may be the result of these responses being sitespecific (Onderdonk and Chapman 2000).…”

Edge Effects on the Density of Cheirogaleus major

“…Therefore, determining how Cheirogaleus major responds to edge effects can provide critical information to understand their ecology. Lehman et al (2006a) found that Cheirogaleus major were more abundant in interior than in edge habitats. However, we were unable to test for clinal variations in densities of Cheirogaleus major and ecological correlates to these patterns.…”

Spatial Variations in Eulemur fulvus rufus and Lepilemur mustelinus Densities in Madagascar

“…For example, of the 6 lemur taxa studied to date for their responses to forest edges in eastern humid forests (Avahi laniger , Cheirogaleus major , Eulemur rubriventer , Hapalemur griseus griseus , Microcebus rufus and Propithecus edwardsi), only C. major had reduced densities in edge habitats [Lehman et al, in press a]. The other 5 lemur taxa existed at either higher densities in edge habitats or they did not display any spatial variations in densities [Lehman et al, 2006a]. Little is known about how other sympatric lemur taxa, such as Eulemur fulvus and Lepilemur sp., respond to forest edges.…”

“…Most lemurs are either unwilling or unable to cross grassland and agricultural fields between forest fragments [Lehman, 2006]. However, many lemurs persist in degraded and edge habitats [Ganzhorn, 1994[Ganzhorn, , 1995Irwin et al, 2005;Lehman et al, 2006a]. For example, of the 6 lemur taxa studied to date for their responses to forest edges in eastern humid forests (Avahi laniger , Cheirogaleus major , Eulemur rubriventer , Hapalemur griseus griseus , Microcebus rufus and Propithecus edwardsi), only C. major had reduced densities in edge habitats [Lehman et al, in press a].…”

“…Thus, I predicted that there should be no spatial variations in densities for L. mustelinus between edge and interior habitats. [Lehman et al, 2006a]. Rainfall amounts average 2,478 mm/year, and the heaviest rains tend to come during the warm, wet season from December to March [Lehman, unpubl.…”