Lemurs in evergreen littoral forest fragments

Lemur species assemblages on Madagascar show highly nested structures in forest fragments of different size. This allows us to predict with a high degree of probability which species will most likely go extinct if the available habitat decreases in size. We use this predictable pattern to identify the minimum viable populations of different lemur species that were able to survive for 20-40 years in forest fragments. According to this analysis, populations of about 40 adult individuals are able to survive for 20-40 years. Populations of this size require between 20 and 800 ha of suitable forest. Fragments of this size no longer exist in the littoral forests of the southeastern portion of the island and are rare in the western dry deciduous forests.

International Journal of Primatology

The alarming rate of deforestation in Madagascar is driving some endemic primates to extinction. Surprisingly, anthropogenic habitat disturbance is not always deleterious. The effect of disturbance on lemur abundance may be related to diet, with frugivorous species more prone to population declines than folivores or insectivores. To test the effects of disturbance on lemur abundance and group size, we surveyed 2 sites within contiguous forest at Ranomafana National Park, 1 lightly disturbed primary forest (Vato) and 1 heavily logged forest (Tala). We quantified forest structure variables along 6 survey routes and conducted 68 diurnal and 42 nocturnal lemur surveys. Canopy closure, canopy height, and understory visibility were greater in Vato than in Tala. We encountered 2 frugivorous lemurs (Eulemur rufifrons, Varecia variegata) and 1 folivore (Avahi peyrierasi) significantly more frequently in Vato than in Tala, whereas the opposite was true for the insectivorous Microcebus rufus. Rates did not differ statistically for 1 frugivore (Eulemur rubriventer) and 2 folivores (Propithecus edwardsi, Hapalemur griseus). Comparisons across the 6 survey routes suggest that the abundance was heterogeneous within as well as between sites. Neither group size nor composition differed between sites. Encounter rates for Varecia variegata were positively related to canopy closure, and encounter rates for Avahi peyrierasi were positively related to canopy height. Encounter rates for Microcebus rufus were negatively related to canopy closure, height, and understory visibility. Similar to other studies, the results suggest that some lemurs, including folivores, may cope with anthropogenic disturbance better than others, including some frugivores. Lemur abundance is heterogeneous, though, even on small spatial scales.

American Journal of Primatology, 2019

Habitat loss and fragmentation are major ecological forces threatening animal communities across the globe. These issues are especially true in Madagascar, where forest loss is ongoing. We examined the effects of forest fragmentation on the distribution and abundance of sympatric, endemic gray, and golden-brown mouse lemurs (Microcebus murinus and Microcebus ravelobensis), the endemic western tufttailed rat (Eliurus myoxinus), and the invasive black rat (Rattus rattus) in two regions in northwestern Madagascar. We used systematic capture procedures in 40 forest fragments and four continuous forest sites which differed in size, shape, and degree of isolation. With a trapping effort of 11,567 trap nights during two dry seasons (2017-2018), we captured 929 individuals (432 M. ravelobensis, 196 M. murinus, 116 E. myoxinus, and 185 R. rattus). We examined the influence of study region, forest type (fragment vs. continuous), forest size, forest shape, the proportion of 50-m forest edge and distance to continuous forest on the abundance and interaction of the four species. Responses to fragmentation differed strongly between species, but no interaction could be detected between the abundance of the different species. Thus competition within and between native and invasive species may not be regulating abundances in these regions. On the contrary, the abundance of M. ravelobensis and E. myoxinus differed significantly between study regions and was negatively affected by fragmentation. In contrast, there was no evidence of an impact of fragmentation on the abundance of M. murinus. Finally, the invasive R. rattus responded positively to the increasing distance to the continuous forest. In conclusion, the response of small Malagasy mammals to forest fragmentation varies largely between species, and fragmentation effects need to be examined at a species-specific level to fully understand their ecological dynamics and complexity.

To make a preliminary assessment of demography of the population of collared and ring-tailed lemurs populations of Ambatotsirongorongo forests in South Eastern Madagascar. To locate few groups of the two species for a longer-term study of the ecological interactions between these two species To make a preliminary survey of the vegetation and habitats.

Madagascar Conservation & Development, 2011

The distribution and abundance of Danfoss' mouse lemurs (Microcebus danfossi) and Grewcock's sportive lemurs (Lepilemur grewcockorum), two regional endemics from north� western Madagascar, were studied from May to December 2008 in the Sofia region between the rivers Sofia and Maevarano.

Habitat destruction and fragmentation are the main threats to the lemurs of Madagascar. The extent of impact of habitat alteration on a species is manifold and not clearly predictable without knowing the species’ ecology and habitat preferences. This study examined baseline aspects of the ecology and behaviour of the Critically Endangered Sahamalaza sportive lemur (Lepilemur sahamalazensis). Study aims were to identify the lemurs’ requirements regarding home ranges and sleeping sites, to investigate the influence of habitat degradation on the lemurs’ ecology and behaviour, to describe its’ vocal repertoire and to develop a non-invasive acoustic tool for rapid species identification. Data collection was conducted in the Ankarafa Forest, Sahamalaza, during three successive field seasons, amounting to twelve months of fieldwork from 2009 to 2011. For habitat descriptions of fragments and microhabitats I used the quarter point sampling method, for home range habitat descriptions a plot-...

Lemur News, 2021

Habitat fragmentation and degradation are serious threats to biodiversity. Knowledge on rare species' demography in disturbed habitat is relevant for conservation plans. In Madagascar, habitat alteration is known to affect both lemur density and distribution. We conducted a 40-day daylight census of an endangered lemur species, the red-bellied lemur (Eulemur rubriventer), in a fragmented and degraded forest in the southern part of its geographic range. With this preliminary study, we report that this species occurs in small fragments and populates a mosaic area east of the Ranomafana National Park, in southeastern Madagascar. Using a total count method, we estimated a minimum population of 30 individuals, a density of 1.05 individuals/km2, and a mean group size of 3.3 individuals. Slash-and-burn agriculture, logging, and the presence of free-ranging dogs appear as the major threats to lemur survival and likely contributed to the disappearance of three species (Eulemur rufifrons, Propithecus edwardsi, Varecia variegata). In the future, management strategies based on field data will be crucial to the survival of the lemur population in the Ranomafana area, which is likely home to the largest population of red-bellied lemurs.

Primates, 2016

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, north eastern Avahi mooreorum and Lepilemur scottorum, and Microcebus sp. Distance sampling surveys were conducted on 11 transects, covering a total of 33km after repeated transect walks. We collected data on tree height, bole height, DBH, 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 1-1.5 ind./km (Microcebus sp.), 0-1 ind./km (Avahi mooreorum) and 0-1 ind./km (Lepilemur scottorum). Species density estimates were calculated at 232.31 ind./km 2 (Microcebus sp.) and 121.21 ind./km 2 (Avahi mooreorum), while no density estimate is provided for Lepilemur scottorum due to a small sample size. Microcebus sp. were most tolerant to habitat disturbance, exhibiting no significant effect of forest type on abundance. Their small body size, omnivorous diet and generalised locomotion appear to allow them tolerate a variety of habitat disturbance. Whereas both Avahi mooreorum and Lepilemur scottorum showed significant effects of forest type on their respective abundance. This study suggests that the specialist locomotion and diet of Avahi mooreorum and Lepilemur scottorum makes them susceptible to the effects of increasing habitat disturbance.

Madagascar's ecosystems are subject to high levels of anthropogenic disturbance and stochastic events, including cyclones. We investigated the abundance of grayheaded lemurs (Eulemur cinereiceps) and vegetation structure in the fragmented forest of Manombo from 1995 to 2007, including 10 yr following Cyclone Gretelle in January 1997. We predicted that the density of this arboreal, frugivorous lemur would be similar in the pre-and post-cyclone intervals only if tree measures demonstrate trends toward recovery in the post-cyclone period. Initial impacts included severe damage to over 60 percent of trees. After 10 yr, all vegetation metrics except for stem density remained low relative to the pre-cyclone period, including dbh, height, and basal area. To investigate vegetation changes separately from cyclone effects, we compared forest structure in the pre-cyclone period alone. Basal area declined but dbh and stem density did not vary between 1995 and 1997; thus, anthropogenic activities or other factors did not consistently alter forest structure in this 2-yr period. Subsequent changes may be linked to cyclone response, presumably in synergy with human disturbance. Contrary to predictions, recent gray-headed lemur population densities were nearly identical to those recorded in 1995 (13.5 AE 3.2 vs. 13.6 AE 6.4 individuals/km 2 , respectively). Lemur populations may have remained stable or declined initially and then recovered in the last 10 yr. Life history and ecological adaptations may explain their resistance or resilience when faced with habitat change. Recent models suggest that lemurs have evolved in response to unpredictable environmental conditions. Such environmental variability may increase with projected climate change.

The Tsitongambarika (TGK) Forest in the south-eastern corner of Madagascar was recently assessed by the IUCN as an area of highest conservation priority and still contains some of the last areas of lowland rainforest in the country. We conducted a preliminary survey of lemur abundance within the Ampasy Valley, in the northern section of the TGK Forest, in July 2012. Line transect sampling was used to determine the abundance of lemur species. Results from our survey showed that lemur abundance was low in Ampasy, although the forest was structurally relatively undisturbed. Our results are in agreement with previous reports showing very low lemur abundance in TGK compared with other areas. The synergistic effect of a natural low abundance and the growing slash-and-burn cultivation and hunting should be carefully considered in ongoing conservation plans to preserve viable lemur populations.