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Conservation of mammalian species diversity in Ambohitantely Special Reserve, Madagascar
Abstract
Ambohitantely Special Reserve protects one of the few remaining remnants of native forest on the Central Plateau of Madagascar, yet its fauna is poorly studied. This paper describes the first systematic small mammal trapping programme to be implemented in the reserve. Between August 1988 and March 1990, Sherman and pitfall traps revealed the presence of four endemic tenrec species and an introduced rat. Diurnal and nocturnal surveys recorded three lemur species. The terrestrial mammal community of Ambohitantely is compated with other reserves in Madagascar. It is concluded that the reserve has a relatively species-poor mammal fauna which may be due to its isolation from contaguous forest blocks. It is postulated that the continued presence of wild boar and domestic cattle in the reserve and regular burning of the surrounding savannah have a detrimental effect on the native fauna and flora. The consequences for conservation are discussed.
... Pitfall and Sherman trapping have both been used effectively to survey small mammals in Madagascar (Stephenson et al., 1994;Goodman and Rakotondravony, 2000), however the success of the two techniques varies. Consequentially, in addition to the pitfall traps 30 Sherman live traps (9 · 8 · 23 cm, H.B. Sherman Traps Inc., Orlando, Florida) were employed for five consecutive nights within each study site. ...
... Three parallel transects of Sherman traps, 10 traps per transect spaced at 10 m intervals and one trap per station (Stephenson, 1995), were placed at 10 m from pitfall traps. The first line and last line of traps was placed at ground level and the middle line was arboreal >1 < 2 m from the ground (Stephenson et al., 1994). Traps were placed within 1 m of the trap station in suitable microhabitat and covered with vegetation to protect them (Gurnell and Flowerdew, 1990). ...
... This species is nocturnal and terrestrial, resting during the day inside fallen dead logs (Stephenson, 2003). It is strictly insectivorous with a preference for termites and ants (Nicoll and Rathbun, 1990;Stephenson et al., 1994). This species showed a positive correlation with availability of termite mounds (Table 6) and the loss of termites as a result of clearing, along with a reduction in potential resting sites, may be the cause of loss of this species. ...
Madagascar is a global biodiversity hotspot threatened by forest loss, degradation and fragmentation, all of which are detrimental to the future survival of forest-dwelling organisms. For conservation purposes it is essential to determine how species respond to habitat disturbance, specifically deforestation. In this study we investigated the impacts of deforestation on three vertebrate communities, lizards, small mammals and birds, in an area of spiny forest subjected to anthropogenic forest clearance. Spiny forest has high levels of endemism, but conservation in this unique ecosystem is hindered by the lack of research. We undertook standardised trapping, time-constrained and timed species searches to assess species richness, species abundance and community composition of lizards, small mammals and birds in six areas of ‘forest’ and six ‘cleared’ areas. From surveys and opportunistic sightings we recorded a total of 70 species of birds, 14 species of mammals and 38 species of reptiles and amphibians. We found forest clearing to have a negative effect on species richness and community structure of all groups and identified loss of canopy cover as a driving factor behind this. However, the response and sensitivity to clearing varied between groups and species. Lizards (50%) and small mammals (40%) had the greatest decline in species richness in response to clearing as compared to birds (26%), although birds showed the greatest shift in community structure. The community in cleared areas contained more generalist and introduced species that have wider geographic ranges and habitat preferences, than those unique to the spiny forest. We found the first suite of species to suffer from forest clearance were those of high conservation priority due to their restricted geographic range. Our findings are discussed in relation to future spiny forest conservation and management.
... Data on ecological variables and species richness in national parks, special reserves, and other protected areas were compiled from the literature (Table 1 and Figure 4). Raw data were obtained from Humbert (1965); Donque (1972); Koechlin (1972); White (1983); Nicoll and Langrand (1989); Evans et al. (1994); Mittermeier et al. (1994); Raxworthy andNussbaum (1994, 1996); Stephenson et al. (1994); Jenkins et al. (1996); DuPuy and Moat (1996); Goodman (1996Goodman ( , 1998; Sterling and Ramaroson (1996); Goodman and Patterson (1997); Schmid and Smolker (1998); Feistner and Schmid (1999); Goodman and Pidgeon (1999) and references therein, Andrianarimisa et al. (2000); Goodman and Rakotondravony (2000); Irwin et al. (2000); Goodman and Rasolonandrasana (2001); and Ratsimbazafy (2002). Species richness was defined as the number of primate, mammal, reptile, bird, and amphibian species recorded from each locale. ...
... Subsequent census in that locale (Irwin et al., 2000) revealed four additional primate species, placing it much closer to regression lines for a locale of its size and vegetational diversity (Figures 6 and 9). Alternatively, other factors such as high human hunting pressure or habitat fragmentation may be associated with lower than predicted species richness, as has been suggested in areas such as Manombo Special Reserve (Ratsimbazafy, 2002) and Ambohitantely (Stephenson et al., 1994). ...
Madagascar contains a diversity of endemic species. Yet levels of species richness vary among the isolated habitats scattered
across the island. A number of ecological factors have been advanced to account for patterns of species richness. In particular,
abiotic factors such as habitat area, latitude, altitude, temperature, and rainfall have been suggested to account for ultimate
differences in the number of species a habitat may support. Biotic variables such as vegetation type have been suggested as
more proximate factors in determining the diversity of habitats available for animals to occupy. Several studies have included
Malagasy locales in evaluating large-scale relationships between ecological variables and species richness (e.g., [Reed and Fleagle, 1995], [Fleagle and Reed, 1996]; [Eeley and Lawes, 1999]; [Emmons, 1999]; [Ganzhorn et al., 1999]). This study combines data on geography, topography, climate, and vegetation with species lists from 27 national parks,
reserves, and other protected areas to specifically address biogeographic patterns of species richness on Madagascar. Ecological
variables are considered individually in order to determine which biotic and abiotic factors may best predict primate, mammal,
bird, reptile, and amphibian richness.
... Small mammal trapping has been successfully used for decades to monitor populations [e.g., 5,6] and inform conservation questions [e.g., [7][8][9]. For example, in south Africa trapping across functional groups provided information on impacts of agriculture practices adjacent to conservation lands [10], and Sherman and pitfall traps were effective in capturing small mammals in Madagascar to determine impacts from forest isolation and presence of wild boar and cattle [11]. Small mammal trapping has also provided data for deriving species richness, density, and population abundance estimates, which can then be used to evaluate climate-richness relationships [12] or related to habitat complexity, land use, and communities [e.g., [13][14][15][16][17]. ...
Few studies have evaluated the optimal sampling design for tracking small mammal population trends, especially for rare or difficult to detect species. Spatially explicit capture-recapture (SECR) models present an advancement over non-spatial models by accounting for individual movement when estimating density. The salt marsh harvest mouse (SMHM; Reithrodontomys raviventris) is a federal and California state listed endangered species endemic to the San Francisco Bay-Delta estuary, California, USA; where a population in a subembayment has been continually monitored over an 18-year period using mark-recapture methods. We analyzed capture data within a SECR modeling framework that allowed us to account for differences in detection and movement between sexes. We compared the full dataset to subsampling scenarios to evaluate how the grid size (area) of the trap design, trap density (spacing), and number of consecutive trapping occasions (duration) influenced density estimates. To validate the subsampling methods, we ran Monte Carlo simulations based on the true parameter estimates for each specific year. We found that reducing the area of the trapping design by more than 36% resulted in the inability of the SECR model to replicate density estimates within the SE of the original density estimates. However, when trapping occasions were reduced from 4 to 3-nights the density estimates were indistinguishable from the full dataset. Furthermore, reducing trap density by 50% also resulted in density estimates comparable to the full dataset and was a substantially better model than reducing the trap area by 50%. Overall, our results indicated that moderate reductions in the number of trapping occasions or trap density could yield similar density estimates when using a SECR approach. This approach allows the optimization of field trapping efforts and designs by reducing field efforts while maintaining the same population estimate compared to the full dataset. Using a SECR approach may help other wildlife programs identify sampling efficiencies without sacrificing data integrity for long term monitoring of population densities.
... Systematic monitoring of biodiversity is required in African and Malagasy protected areas (e.g. Stephenson et al. 1994;Knights et al. 2014;Beaudrot et al. 2016), and small mammals should be integrated into new or existing monitoring programmes. Data collection should include not only the status of species (populations, range, etc.), but also threats, especially offtake and habitat loss. ...
... Re). Lemurs were sighted using strong torches to reflect eye glare (Stephenson et al., 1994). For each observation, the lemur species was recorded along with the time and the number of individuals present. ...
... Small mammal abundance (ie the number of individual animals captured) was generally lower in the present study than in any other forest site trapped in Madagascar. Sherman traps recorded 15.2 captures per 1000 trap nights compared with 25.1 (Nicoll et al. 1988), 36.7 (Stephenson 1993) and 83.8 (Stephenson et al. 1994b) captures in other studies. When pitfall traps of identical size were used successfully elsewhere, captures rates were 2.4 (Nicoll et al. 1988) and 2.5 (Stephenson 1993) individuals per 1000 trap nights, more than twice the rate of the present study. ...
This study describes a systematic small mammal trapping programme in the lowland rain forest of Anandrivola, north-east Madagascar. Trapping in both primary and secondary forest revealed the presence of nine small mammal species. Twenty-six habitat variables measured around each trap site were used to determine microhabitat preferences in the three most common small mammal species. The tenrec Microgale talazaci Major, 1896 was widespread but favoured microhabitats with relatively dense herbaceous growth. The endemic rodent Eliurus webbi Ellerman, 1949 was most often found deep within primary forest, in microhabitats characterized by low herb densities and abundant lianes. The introduced rat Rattus rattus (Linnaeus, 1758) was trapped only in secondary forest, in microhabitats close to the forest edge with dense herbaceous growth. The effects of microhabitat availability on small mammal species distributions and the consequences for conservation are discussed.
... The use of pitfalls to sample small mammals in the tropics is restricted to few studies in Africa (Goodman and Rakotondravony 2000;Maddock 1992; Raxworthy and Nussbaum 1994;Stephenson 1993;Stephenson et al. 1994), in Australia (Laurance 1992), and in South America (Hice and Schmidly 2002;Lyra-Jorge and Pivello 2001;Pardini 2004;Pardini et al. 2005;Voss et al. 2001). Although some of these studies compared the efficiency of pitfalls to traditionally used live traps (Hice and Schmidly 2002;Laurance 1992;Lyra-Jorge and Pivello 2001;Maddock 1992;Voss et al. 2001), their sampling protocols included only small or medium-sized pitfalls, most in the range of 10-20 liters, and almost all 35 liters, which may be inefficient for capturing some species of tropical small mammals, and did not account for temporal or spatial factors that seem likely to influence capture success and to confound comparisons among methods. ...
Using standardized small mammal surveys at 26 Atlantic Forest sites, we evaluated the efficiency and compared the weight of captured species and individuals between large pitfall traps and Sherman traps. We also investigated the effects of climatic variables on daily capture success of pitfalls. Pitfalls were clearly more efficient than Sherman traps, capturing 29 species, of which 16 were captured exclusively with this method, mostly represented by rare species. In contrast, Sherman traps captured 14 species, of which just 1 was not captured with pitfall traps. Compared to Sherman traps, pitfalls captured (per site) 3 times the number of species, 2 times the number of individuals, and significantly more individuals of 7 species. Despite differences in sampling efficiency, positive correlations suggest that at least coarse-scale variation among sites for several assemblage parameters are congruent between the 2 trapping methods. Sherman traps tended to capture adults, whereas pitfalls captured individuals over a broader range of weight classes or tended to capture more juveniles. Total daily capture rates in pitfall traps increased with precipitation. Our results suggest that large pitfall traps are effective at capturing rare species and juveniles, probably because they are less selective, and are thus essential for inventorying the rich and poorly known small mammal fauna of the tropics and for demographic studies.
... Considering the high rate of endemism in the Malagasy bird community and the threat of continued deforestation and habitat degradation on the island, it is critical to identify the bird communities in all of Madagascar's different ecosystems to define baselines for the development of conservation strategies (Jolly et al. 1984; Stephenson et al. 1994; Hannah et al. 1998; Dumetz 1999). Within the past decade, research in Madagascar has increasingly focussed on describing the communities of previously unsurveyed habitats (Safford and Duckworth 1988; Goodman 1993; Goodman and Putnam 1996; Goodman et al. 1996a; Thornstrom and Watson 1997; Dumetz 1999) and on the ecology of endangered bird species (Wilme and Langrand 1990; Goodman et al. 1996b; Thorstrom and Lind 1999). ...
The littoral forests of Madagascar are relatively unexplored ecosystems that are considered seriously threatened by deforestation and habitat fragmentation. We set out to describe the bird communities inhabiting the littoral forest remnants in three different sub-regions of southeastern Madagascar to determine the national importance of these forests for bird conservation. In total, 77 bird species were found inhabiting 14 littoral forest remnants. Of these species, 40 are endemic to Madagascar and a further 21 are endemic to the Indian Ocean sub-region, consisting of Madagascar, the Comoros and the Mascarenes. The matrix habitats (Melaleuca forests, marcage swamp forest, Eucalyptus plantations and Erica grassland) that immediately surround the littoral forests were depauperate of bird species and contained few species that were found within the littoral forests. The geographic location of littoral forest remnants had an important role in determining what bird species occurred within them, with the northern remnants having similar bird communities to nearby humid forest whilst the most southern remnant had a bird community that resembled those of nearby spiny forest habitats. Eleven bird species that have been previously described as being habitat-restricted endemics to either spiny forests or humid forests, were found in littoral forest remnants. These results suggest that these littoral forests may play an important transitional role between the two other major natural habitats (spiny forest and humid forest) of southeastern Madagascar. On this basis we advocate that the littoral forest remnants of southeastern Madagascar should be afforded continuing conservation priority.
... Bats make a significant contribution to mammalian species richness and biomass in the tropics, but despite the extensive amount of previous research on Madagascar's vertebrates (Goodman and Benstead 2003) there have been few ecological studies on Malagasy Chiroptera (Eger and Mitchell 2003 ). Research biologists have traditionally focused on the island's endemic land mammals with lemurs, rodents and tenrecs being popular topics of study (e.g. Stephenson et al. 1994; Ramanamanjato and Ganzhorn 2001; Ganzhorn et al. 2003; Kappeler and Rasoloarison 2003). Until recently the taxonomy of Malagasy bats was based mainly on a series of collections made in the 1970s (Peterson et al. 1995) and ecological information was almost completely lacking. ...
Although the land mammals of Madagascar have been the subject of many studies, the island’s bats have yet to feature prominently
on the research or conservation agenda. In this study we used mist nets, acoustic sampling and cave surveys to assess habitat
use, seasonality and roost selection. Four microchiropteran species (Triaenops rufus, T. furculus, Miniopterus manavi and Myotis goudoti) appeared to be strongly associated with the forest interior based on trapping, but analysis of time-expanded echolocation
recordings revealed that T. rufus and M.␣manavi were frequently recorded in forest edges and clearings. Bat activity was significantly lower inside the forest than at the
interface between agricultural land and forest. The caves visited most often by tourists were low in bat abundance and species
richness. Anjohikinakina Cave, which was visited infrequently by people, was used by five species and contained between 54%
(winter) and 99% (summer) of bats counted in 16 caves and is a site of national importance for bat conservation. Hipposideros commersoni was only netted in our study area during October and may be a migrant to the site or present but inactive during the austral
winter. The forest surrounding the caves is therefore important because it provides cover for emerging bats and a potential
source of invertebrate prey whilst the forest edge is important to foraging bats.
KeywordsAcoustic sampling-Caves-Chiroptera-Forest dependency-Karst-Roost
... In Madagascar, R. rattus has penetrated remote, undisturbed, humid forest where it can be abundant while native rodent density and species richness are depressed (Goodman 1995;Goodman et al. 1996Goodman et al. , 1997Ganzhorn et al. 2003). Although the mechanism of displacement is uncertain, it is interesting to note the apparent absence of evidence for negative interspecific impact at lower altitude sites relative to the distributional and abundance patterns observed at higher altitudes (Stephenson 1993(Stephenson , 1995Stephenson et al. 1994;Goodman et al. 1996Goodman et al. , 1997Ramanamanjato and Ganzhorn 2001;Ganzhorn 2003;Ganzhorn et al. 2003). A mechanism that may help to explain this discrepancy and cast new light on the interactions between introduced and native rodents in Madagascar is disease transmission. ...
In this first comprehensive review of negative effects of introduced rodents on insular small mammals, the focal species Rattus rattus, R. norvegicus, R. exulans and Mus musculus are implicated in at least 11 extinctions. Furthermore, removal experiments, eradication campaigns and control programmes
provide evidence for negative effects on extant populations. While data are currently insufficient for meaningful generalisation
with regard to the most threatening rodents, the most threatened small mammals, and the true extent of the problem, it is
interesting that R. rattus is implicated in the majority of impacts. This may be explained by its extensive distribution and ecological plasticity.
I conclude with methodological recommendations to guide data collection for impact quantification and the study of impact
mechanism. This information should facilitate the prioritisation and justification of eradication campaigns, control programmes
and biosecurity measures while ensuring that much-needed attention is paid to the conservation of insular small mammals.
... Disturbance in forest habitats is a major threat to the integrity of Madagascar's remaining naturally forested areas (Raxworthy, 1988;Stephenson et al., 1994;Smith et al., 1997;Merelender et al., 1998). Previous work in Madagascar compared the use of primary and secondary forest by endemic mammals (e.g. ...
Many chameleon species are thought to be restricted to primary rainforest where they are threatened by the continued fragmentation and degradation of natural vegetation. We surveyed chameleon abundance in forest subject to high disturbance, low disturbance and in a riparian zone in Madagascar. Four Calumma species and Brookesia thieli were present in all habitats, but B. minima was not recorded from the high-disturbance forest. Chameleons were more abundant in rainforest subject to low-disturbance (e.g. selective timber extraction) than in patches of high-disturbance forest that was recovering from burning. Riparian zones within low-disturbance forest provided linear patches of high chameleon abundance and are therefore an important conservation resource because they also protect a range of other endemic and threatened species. Carefully designed management plans are needed to conserve biodiversity and allow the sustainable use of forest products by people in Madagascar.
The mammal family Tenrecidae (Afrotheria: Afrosoricida) is endemic to Madagascar. Here we present the conservation priorities for the 31 species of tenrec that were assessed or reassessed in 2015–2016 for the IUCN Red List of Threatened Species. Six species (19.4%) were found to be threatened (4 Vulnerable, 2 Endangered) and one species was categorized as Data Deficient. The primary threat to tenrecs is habitat loss, mostly as a result of slash-and-burn agriculture, but some species are also threatened by hunting and incidental capture in fishing traps. In the longer term, climate change is expected to alter tenrec habitats and ranges. However, the lack of data for most tenrecs on population size, ecology and distribution, together with frequent changes in taxonomy (with many cryptic species being discovered based on genetic analyses) and the poorly understood impact of bushmeat hunting on spiny species (Tenrecinae), hinders conservation planning. Priority conservation actions are presented for Madagascar's tenrecs for the first time since 1990 and focus on conserving forest habitat (especially through improved management of protected areas) and filling essential knowledge gaps. Tenrec research, monitoring and conservation should be integrated into broader sustainable development objectives and programmes targeting higher profile species, such as lemurs, if we are to see an improvement in the conservation status of tenrecs in the near future.
Rhabdias blommersiae sp. n. (Nematoda: Rhabdiasidae) is described from the lungs of Domergue's Madagascar frog, Blommersia domerguei (Guibé) (Amphibia: Mantellidae), in Madagascar. The new species differs from congeners parasitizing amphibians in having a smaller body and buccal capsule, six equal lips, large excretory glands of unequal length and a posteriorly inflated body vesicle. A combination of characters distinguishes it from Afromalagasy species of Rhabdias Stiles et Hassall, 1905. Rhabdias blommersiae is the third species of the genus described from amphibians in Madagascar. Close similarities in the number and shape of circumoral structures in two Rhabdias species described from mantellid hosts in Madagascar suggest a close relationship and common origin of the two species, with subsequent adaptation to separate hosts within the Mantellidae.
A small mammal survey of the Lipotyphla (Tenrecidae and Soricidae) was conducted in the montane forest of the Réserve Spéciale d'Ambohitantely, Central High Plateau, Madagascar. Species richness of this group was assessed using standardized pit-fall trap techniques in a control site of 1250 ha and four smaller forest fragments (136, 30, 12 and 0.64 ha). The forests of this reserve are highly fragmented, isolated for many decades and about 90 km from the nearest large forest block. On the basis of pit-fall captures, lipotyphlan diversity was highest in the control site with nine species, including eight endemic taxa. The number of species declined progressively with diminishing forest size. The species richness found in the control site, the largest remaining block within the reserve, is comparable to other much more extensive forest blocks at parallel elevations and with similar botanical communities. Thus, it seems that the lipotyphlan community within the control site has not experienced notable local extinctions. The introduced Soricidae, Suncus
murinus, has colonized the Ambohitantely forests. However, there is no evidence of competition between this species and members of the family Tenrecidae, particularly Microgale, as has been postulated in the literature.
Studies on the effects of nonindigenous invasive species and habitat fragmentation on native ecosystems have become priorities for conservation biologists. This is relevant particularly for islands with high degrees of endemism. In the present paper the role of fragmentation and possible effects of introduced Rattus rattus on endemic rodents (Macrotarsomys bastardi and Eliurus spp.) and the gray mouse lemur (Microcebus murinus) were assessed for dry deciduous forests in Madagascar. Capture rates of endemic rodents declined significantly with declining fragment size. Macrotarsomys bastardi was never caught in primary forest fragments < 600 ha or outside the primary forest but captures of M. bastardi were correlated to changes in vegetation structure associated with fragmentation rather than to fragment size per se. Eliurus spp. were also found in small primary-forest fragments and in secondary forests close to primary forests, suggesting that secondary forests can serve as buffer zones or corridors for this species. The lemur M. murinus was caught in all types of primary and secondary forest. This species did not seem to respond to fragmentation of primary forests. Even though it was found in most secondary-forests, capture rates declined as these secondary forest formations increased in size. This indicates that secondary forests are suboptimal habitats for M. murinus. Rattus rattus were caught in all vegetation formations except for the open savanna. Their capture rates increased as forest fragments became smaller, indicating that mosaics of different habitat types are beneficial for introduced rats. There was no significant relation between capture rates of R. rattus and the endemic species. In conclusion, these results suggest that (1) native Malagasy rodents of the dry deciduous forest are more sensitive towards forest disturbance than M. murinus; (2) there is no indication for negative interactions between introduced rats and the native small-mammal fauna.
Based on cartography, floristic inventory and vegetation analysis in the north and south of the Eastern Domain of Madagascar we identified three original tropical rainforest types which are among the world's most biodiverse known sites for plants: the littoral forest on sand, the lowland forest on gneiss and the lowland forest on basalt. Floristic and structural comparisons were conducted on 37 plots of 5010m. Multivariate analysis indicates that floristic composition is correlated with abiotic factors of rainfall, latitude, soil composition, and marine influence; the structure of the undergrowth is generally homogeneous and the canopy is more or less open. Many reserves must be created on gneiss, sand and basalt all along the eastern coast to preserve biodiversity from the deforestation process. On basalt, this is especially urgent because about only 10 000 ha of a very ancient forest that shelters numerous botanical novelties remain today.
Leaf litter and soil of tropical forests harbour some of Earth's most diverse, most endangered, yet least understood biological communities. How well do east-southeast Madagascar's reserves protect this resource? A preliminary answer is provided by the landsnail genera Cyclophoridae Boucardicus and Charopidae n. gen., as represented by 3680 specimens in 64 species, collected 1990–1993 from 129 stations in 26 transects, with nine reserves included. These two genera qualify as indicator/target taxa because they are endemic, species-rich, well-defined clades, sensitive to environmental degradation, with species readily identifiable by shells alone. Indices of diversity and endemism were used to rank 12 bioclimate-latitude regions by priority for conservation/collection. The higher-priority regions generally have some forest nominally conserved, of which the lowland-rainforest reserves of Manombo, Kianjavato, and Betampona are especially rich. A crucial exception, however, is the highest-priority region: the coastal-montane rainforests to the north of Tolagnaro (Fort Dauphin), which are completely unprotected and are rapidly being destroyed. (Andohahela Reserve hes westward, where diversity and endemism are 60% and 20% lower, respectively, so it conserves less than a fourth of the general region's endemic diversity.)
In Ambohitantely the rainforest is divided distinctly by pseudosteppe into more than 500 fragments. The amphibian faunas of seven such fragments varying in size from 0.16 to 1250 ha were examined. Twenty-eight amphibian species of two families (Ranidae and Microhylidae) were recorded in the rainforest fragments. The species numbers in the fragments were positively correlated with fragment area and form nested subsets. Composition and individual frequency in small fragments differed from that of the control site (1250 ha). The relative individual density (individuals found each searching hour) was negatively correlated with the fragment size. This is probably due to the fact that the density of streams and brooks was higher in small fragments, which also explains why smaller fragments contained a larger proportion of brook-dwelling amphibian species than larger fragments. Species that live far from water and show a reproduction strategy independent of running waters or ponds, such as certain microhylids, were only present in fragments of 30 ha or more. The more common species in the control site were also found in the majority of fragments. A rainforest remnant of 1250 ha seems to be large enough to contain a large part of the original amphibian fauna, provided that there are suitable microhabitats. Compared to other taxa, amphibians generally seem to react less sensitively to fragmentation. Due to the sensitivity to microclimate changes microhylids and certain species of the subfamily of Mantellinae represent good bioindicators.
The vocal behaviour of wild indris inhabiting the area near Andasibe was studied by means of all occurrence sampling. We provide a quantitative overview of the vocal repertoire of Indri indri, describing qualitative contextual information and quantitative acoustic analysis for all the utterances we recorded from adult individuals. Other than the song, the repertoire of Indri indri comprises 8 vocal types uttered by the adults. Future studies are necessary to explore whether vocalisations uttered in different contexts have different functions and how these functions relate to acoustic structure.
Four categories of islands in SE Asia may be identified on the basis of their histories of landbridge connections. Those islands on the shallow, continental Sunda Shelf were joined to the Asian mainland by a broad landbridge during the late Pleistocene; other islands were connected to the Sunda Shelf by a middle Pleistocene landbridge; some were parts of larger oceanic islands; and others remained as isolated oceanic islands. The limits of late Pleistocene islands, defined by the 120 m bathymetric line, are highly concordant with the limits of faunal regions. Faunal variation among non-volant mammals is high between faunal regions and low within the faunal regions; endemism of faunal regions characteristically exceeds 70%. Small and geologically young oceanic islands are depauperate; larger and older islands are more species-rich. The number of endemic species is correlated with island area; however, continental shelf islands less than 125 000 km2 do not have endemic species, whereas isolated oceanic islands as small as 47 km2 often have endemic species. Geologically old oceanic islands have many endemic species, whereas young oceanic islands have few endemic species. Colonization across sea channels that were 5–25 km wide during the Pleistocene has been low, with a rate of about 1–2/500000 years. Comparison of species-area curves for mainland areas, late Pleistocene islands, and middle Pleistocene islands indicates that extinction occurs rapidly when landbridge islands are first isolated, with the extent of extinction dependent upon island size; extinction then slows to an average rate of 1–2%/10 000 years. The great majority of the non-volant Philippine mammals arrived from the Sunda Shelf, the geographically closest of the possible source areas. Speciation within the Philippines has contributed substantially to species richness, perhaps exceeding colonization by a factor of two or more as a contributor to species number. Colonization, extinction and speciation rates differ among taxonomic groups, with murid rodents being most successful and carnivores least successful. In order for any model of island biogeography to be widely applicable to insular faunas, the model must include speciation as a major variable. It is suggested that insular mammalian faunas typically are not in equilibrium, because geological and climatic changes can occur as rapidly as colonization and speciation.
This study represents the first long-term small mammal survey of the mid-altitude rain forest reserve of Analamazaotra, Madagascar. Twenty-three visits were made to the reserve between April 1988 and May 1990. Live-trapping with Sherman and pitfall traps at four sites subjected to varying levels of human disturbance revealed the presence of seven endemic tenrec species, three endemic rodent species and an introduced rat. Greater species richness was demonstrated at the most undisturbed site, though individual species abundance was reduced. Human disturbance associated with tourism was correlated with a decrease in endemic species richness and an increase in abundance of introduced rats. Forest subjected to infrequent logging by local people exhibited an intermediate level of species richness. It is recommended that core areas of the reserve be left undisturbed in order to preserve small mammal species diversity.
A fundamental question in ecology is how many species occur within a given area. Despite the complexity and diversity of different ecosystems, there exists a surprisingly simple, approximate answer: the number of species is proportional to the size of the area raised to some exponent. The exponent often turns out to be roughly 1/4. This power law can be derived from assumptions about the relative abundances of species or from notions of self-similarity. Here we analyze the largest existing data set of location-mapped species: over one million, individually identified trees from five tropical forests on three continents. Although the power law is a reasonable, zeroth-order approximation of our data, we find consistent deviations from it on all spatial scales. Furthermore, tropical forests are not self-similar at areas </=50 hectares. We develop an extended model of the species-area relationship, which enables us to predict large-scale species diversity from small-scale data samples more accurately than any other available method.
When man, concerned with his health, studied the influence of bad air (malaria) and of poisonous emanations from the ground less than a century ago, did he not practice ecology without knowing it? The idea that there is a close correlation between the environment and diseases belongs to the common heritage of human knowledge.
Madagascar has more prosimians (lemurs) and more diverse species of prosimian than any other region of the world, but true monkeys and apes are missing. Among Carnivora, only the Viverridae are represented. Rodentia are represented by a single subfamily, Nesomyinae. Ungulates have one present-day representative, Malagasy wild boar Potamochoerus larvatus. A Pleistocene aardvark, Plesiorycteropus, did reach the island. A dugong in the coastal water, numerous bats and a series of insectivores completes the fauna. -P.J.Jarvis
It would be inconceivable to study the environment in Madagascar without taking into account the part played by man, even though the settlement of the island is a recent phenomenon, probably covering about two millennia as a maximum1. The environment observed almost everywhere is not as it was originally but is the result of direct or indirect human action. The majority of writers acknowledge this fact, but there are a number of obscure points regarding the intensity, speed and extent of human action in the transformation of the environment, both insofar as concerns the flora and fauna and the erosion systems.
Les Insectivores (Chiroptères exclus) sont représentés dans le domaine malgache par deux familles: celle des Tenrecidae et celle des Soricidae.
Outlines the evidence concerning 1) geographical and chronological patterns of extinction and 2) the chronology and nature of human occupation of the island. Examines competing hypotheses about the relationships between these phenomena, and finally presents a revised model of the human role in Malagasy extinctions, where it is argued that ecological transformation resulted from the substitution of domestic bovids for the native terrestrial herbivores. Causal factors suggested are competition, habitat destruction and fragmentation, and adventitious hunting. -after Author
Reviews current evidence for mass extinctions, principally as a result of tropical forest loss. There is currently little evidence of extinctions at the rates predicted by some theoretical models, but there is ample evidence that the number of species that will require urgent action to prevent their eventual disappearance is increasingly rapidly. These species are "committed to extinction', and will require major interventions if they are to be saved. Increasing numbers of species have fragmented populations and are almost certainly suffering severe genetic erosion. These trends could be setting the stage for much higher rates of extinction in the future. -from Authors
The habitat use and feeding ecology of the introduced Indian black-naped hare Lepus nigricollis nigricollis (Cuvier) was studied on Cousin Island in the Seychelles with a view to assessing the impact of hares on vegetation and thus indirectly on several rare endemic landbirds and some seabird species. Habitat use was assessed by determining the distribution of faecal pellets over the island and mapping the location of hares seen. The dispersion of faecal pellets and hares seen was not uniform; hares showed a strong preference for coastal habitats and the garden in the depression at the base of the granite hill. Analysis of faecal pellets showed that at least 24 of the 130 plants recorded for Cousin were easten by hares. Hares may aid plant seed dispersal, and browsing may prevent the regeneration of Casuarina equisetifolia. This is an important foraging tree for several rare endemic landbirds and is used as nest sites by some seabird species.
A system of natural reserves, each surrounded by altered habitat, resembles a system of islands from the point of view of species restricted to natural habitats. Recent advances in island biogeography may provide a detailed basis for understanding what to expect of such a system of reserves. The main conclusions are as follows:The number of species that a reserve can hold at equilibrium is a function of its area and its isolation. Larger reserves, and reserves located close to other reserves, can hold more species.If most of the area of a habitat is destroyed, and a fraction of the area is saved as a reserve, the reserve will initially contain more species than it can hold at equilibrium. The excess will gradually go extinct. The smaller the reserve, the higher will be the extinction rates. Estimates of these extinction rates for bird and mammal species have recently become available in a few cases.Different species require different minimum areas to have a reasonable chance of survival.Some geometric design principles are suggested in order to optimise the function of reserves in saving species.
The adverse effects of introduced birds and mam- mals on native taxa and ecosystems in Hawaifi have been long term, widespread, and severe. Impacts began at least 1,500 years ago with colonization by the Poly- nesians and their flora and fauna, and continued with their increasingly severe disturbance to the landscape, especially below 500 m elevation. Problems accelerated with the arrival of continental man in 1778, and con- tinue to the present day with suspected deliberate re- leases of birds that threaten native species as re- cently as 1982. Alien vertebrates can affect native biota through predation, competition, depredation, and habitat degradation. Negative impacts can be subtle or dramatic, but evidence of importance is manifested in large percentages of extinct and rare taxa. In this paper, adverse effects of major bird and mammal intro- ductions are outlined where possible for islands, vege- tation zones, and rare taxa. Although much remains to be learned, suggestions for reducing negative effects of alien vertebrates can be made. These include: En- forcement of efficient quarantine procedures; suffi- cient support for enduring and complete vertebrate dam- age control programs (including research, management, and monitoring) on lands managed for preservation of native Hawaiian ecosystems and taxa; development of multiple and adaptable methods of vertebrate damage reduction; preservation and management of the most in- tact areas remaining in Hawai'i; and cooperation and communication among the agencies and special interest groups (including developers and conservationists) in land use planning on regional bases. Cooperative ap- proaches, effective education and communication about the value of protected areas, and the increased useful- ness of such areas for all citizens, are seen as par- ticularly important in reducing continued damage to Hawai'ifs remaining native ecosystems by alien verte- brates.
Thenative muroidrodents inhabiting Mada- gascar arearranged asanendemic subfamily, the Nesomyinae, thatcontains only10species and7 genera according torecent authorities. Thiscon- tribution summarizes thegeographic distribution ofnamedforms basedonexamination ofapprox- imately 750specimens representing 73principal collecting localities. Eachlocality account includes itsgeographic coordinates, thetaxacollected, and miscellaneous remarks onhabitat, collectors, and other relevant data. Abbreviated synonymies are provided forthedescribed forms, listed according tocurrent classifications, aswellasinformation onthelocation oftypelocalities. Theapparent sympatry orcontiguous allopatry ofcertain taxa ofEliurus andNesomys nowviewed assubspecies suggests that thegroupismorespeciose thanpres- ently recognized. Thenotion ofnesomyines asan impoverished faunaisdiscussed fromtheper- spective ofrodent species diversity onotheris- lands within tropical latitudes andinlight ofthe poorspecimen-based documentation thatexists forunderstanding nesomyine taxonomy anddis- tribution.
We used an island-based model to estimate mammal species richness in reserves following isolation of the reserve from surrounding habitat. Model predictions were compared to observed species richness in isolated reserves in the Australian wheatbelt. Our global, island-based model underestimates the total richness in the Australian reserves. However, the model accurately predicts the number of species that forage exclusively on the reserves and not on surrounding farmland. We tentatively conclude that general, island-based models may be useful tools to predict richness on reserves.
The utilization of eucalyptus plantations by seven sympatric species of prosimians was studied in the eastern rainforest of Madagascar. The species were Avahi laniger, Cheirogaleus major, Hapalemur griseus, Indri indri, Lemur fulvus, Lepilemur mustelinus, and Microcebus rufus. None of the lemurs was ever found in young eucalyptus plantations with little undergrowth. This was mainly due to the lack of travel opportunities within the shrub layer and between the shrubs and the canopy. Food (mainly berries) is seasonally available in the shrub layer but cannot be exploited because frugivorous lemurs cannot reach it. Old eucalyptus plantations with dense undergrowth are used by all prosimian species. They provide food as well as travel and resting facilities. Mixed tree plantations in the western part of Madagascar were used by groups of Lemur fulvus, Lepilemur mustelinus, and Propithecus verreauxi. According to these results, old eucalyptus plantations and mixed tree species plantations could be used to provide firewood and construction wood for the human population. They also might extend the habitat for lemurs and serve as buffers against human disturbance.
Although fewer than one-fifth of the world's bird species are restricted to islands, over 90% of bird extinctions during historic times have occurred on islands. The major identified cause has been the effects of exotic animal species introduced by man; the largest number of documented extinctions has occurred on islands of the Pacific Ocean.
Some 39% (402) of threatened bird species are restricted to islands and more than 907; of these are endemic to a single geopolitical unit. The largest numbers occurring in such units are in Indonesia (91) and the Philippines (34). As a region, the Pacific holds more threatened species (110) than any other, including almost half of those considered Endangered and over 40% of the Vulnerable species.
Most threatened island species are forest-dwelling. A high proportion of the Endangered species use seasonal/temperate forest. While habitat destruction now poses the greatest overall threat to island birds (affecting over half the species restricted to islands), the presence of introduced species threatens 30 of the 66 Endangered species.
Although immediate extinctions of island species can best be averted by mitigating the effects of introductions, the removal of native forests will be a more severe problem in the longer term. There is an urgent need for ecologists to provide detailed information on the habitats of both threatened and endemic species so that more appropriate and effective conservation programmes can be developed.
Feral pig Sus scrofa control in Kipahulu Valley, a remote rain forest in Haleakala National Park, Maui, Hawaiian Islands, has been achieved with snares over a 45-month period. Initial pig densities in fenced management units of 6·2 km2 and 7·8 km2 were estimated at 6 animals/km2 and 14·3 animals/km2 for the two units, based on population reconstruction from animals killed and aged. During the 45 months of the study, 1978 snares were set, and 1·6 million snare nights were logged. Snare density reached 96/km2 and 200/km2 for the two management units by the end of the study. A mean effort of 43 worker hours/pig was used to remove 53 pigs from the upper management unit, and a mean of 7 worker hours/pig to remove 175 animals from the more densely populated lower unit. Pig activity monitoring along transects provided a good measure of control effectiveness until densities of about 1 pig/km2 were achieved, after which transects became less useful than scouting for determining pig activity.
Using the terrestrial, non-volant mammalian faunas of land-bridge islands worldwide, we investigated the roles of area and ambient environmental energy in determining species richness. Earlier studies showed that consideration of total island energy (i.e. area times energy per unit area) allows one to formulate a single model applicable to island faunas in different regions. However, we found that variation in ambient energy has a much more pronounced effect on richness than does variation in area. Incorporation of this fact into predictive models eliminates the latitudinal bias in earlier models' prediction of bird and angiosperm species richness. However, latitude was a better predictor of mammalian richness than the energy measures used in our analysis.
Thesis (Ph. D.)--University of Aberdeen, 1991.
The carnivora of Madagascar are divided into 8 genera, 3 subfamilies and just one family, that of the Viverridae. All are peculiar to Madagascar except for the genus Viverricula, which is represented by a single species, Viverricula rasse (Horsfield), which is also found throughout southern Asia and was probably introduced to the island with man.
Insular ecology and conservation. In Conservation biology
- B A Wilcox
Wilcox, B.A. (1980). Insular ecology and conservation. In Conservation biology." an evolutionary-ecological perspec-tive, ed. M.E. Soul6 & B.A. Wilcox. Sinauer Associates, Sunderland, Massachusetts, pp. 95-118.
Lemurs of Madagascar: an action plan for their conservation
- R A Mittermeier
- W R Konstant
- M E Langrand
Mittermeier, R.A., Konstant, W.R., Nicoll M.E. & Langrand, O. (1992). Lemurs of Madagascar: an action plan for their conservation, 1993-1999. IUCN/SSC Primate Specialist Group, IUCN, Gland.
Part 1.1: Family Tenrecidae. In The mammals of Africa: an identification guide
- H Genest
- F Petter
Genest, H. & Petter, F. (1974). Part 1.1: Family Tenrecidae. In The mammals of Africa: an identification guide, ed. J. Meester & W.H. Setzer. Smithsonian Institution Press, Washington DC, pp. 1 7.
Madagascar: revue de la conservation et des aires prot~gkes
- M E Nicoll
- O Langrand
Nicoll, M.E. & Langrand, O. (1989). Madagascar: revue de la conservation et des aires prot~gkes. WWF, Gland.
La for6t d'Ambohitantely
- G Bastian
Bastian, G. (1964). La for6t d'Ambohitantely, Madagascar. Rev. Geogr., 5, 1-42.
The carnivora of Madagascar. In Bio-geography and ecology in Madagascar The Hague
- R Albignac
Albignac, R. (1972). The carnivora of Madagascar. In Bio-geography and ecology in Madagascar, ed. R. Battistini & G. Richard-Vindard. W. Junk, The Hague, pp. 667-82.
The ecology and microhabitat segregation of small mammals within lowland tropical rain forest of north-east Madagascar
- Stephenson
Stephenson, P.J. (1987). The ecology and microhabitat segregation of small mammals within lowland tropical rain forest of north-east Madagascar. BSc Honours thesis, University of London, Egham.
Diversit6 des petits mammif~res en for6t tropicale humide de Madagascar: analyse pr61iminaire. In L'equilibre des (cosystkmes forestiers ~ Madagascar: actes d'un s(mi-naire international
- M E Nicoll
- F Rakotondraparany
- V Randrianasolo
Nicoll, M.E., Rakotondraparany, F. & Randrianasolo, V. (1988). Diversit6 des petits mammif~res en for6t tropicale humide de Madagascar: analyse pr61iminaire. In L'equilibre des (cosystkmes forestiers ~ Madagascar: actes d'un s(mi-naire international, eds. L. Rakotovao, V. Barre & J. Sayer. IUCN, Gland, pp. 241-52.
The tenrecs, a study in mammalian behavior and evolution A possible role of plantations for primate conservation in Madagascar
- J F Eisenberg
- E Gould
Eisenberg, J.F. & Gould, E. (1970). The tenrecs, a study in mammalian behavior and evolution. Smithson. Contrib. Zool., 27, 1 127. Ganzhom, J.U. (1987). A possible role of plantations for primate conservation in Madagascar. Amer. J. Primatol., 12, 205-15.
Lemurs of Madagascar and the Comoros. The IUCN red data book Biogeography of mammals in south east Asia: estimates of rates of colonization, extinction and speciation
- C Harcourt
- J Thornback
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- Gland
- L R Heaney
Harcourt, C. & Thornback, J. (1990). Lemurs of Madagascar and the Comoros. The IUCN red data book. IUCN, Gland. Heaney, L.R. (1986). Biogeography of mammals in south east Asia: estimates of rates of colonization, extinction and speciation. Biol. J. Linnean Soc., 28, 127-63. Heim de Balsac, H. (1972). Insectivores. In Biogeography and ecology in Madagascar, ed. R. Battistini & G. Richard-Vindard. W. Junk, The Hague, pp. 629-60.
‘Normal’ extinctions of isolated populations
- Diamond
Diamond, J.M. (1984). 'Normal' extinctions of isolated popu-lations. In Extinctions, ed. M.H. Nitecki. University of Chicago Press, Chicago, Illinois, pp. 191-246.
Part 1.1: Family Tenrecidae
- Genest
Les rongeurs à Madagascar
- Rakotondravony
La forêt d'Ambohitantely, Madagascar
- Bastian
Insular ecology and conservation
- Wilcox
Diversité des petits mammifères en forêt tropicale humide de Madagascar: analyse préliminaire
- Nicoll