Distribution, status, and conservation of radiated tortoises (Geochelone radiata) in Madagascar

Leuteritz, Thomas; Lamb, Trip; Limberaza, Jean Claude

doi:10.1016/j.biocon.2005.02.003

Cited by 39 publications

(32 citation statements)

References 22 publications

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“…As in previous works, we found that detectability was affected by individuals’ age class: juveniles versus adults [29, 30, 41]. On the other hand, density was also affected by habitat patches and sites.…”

Section: Discussionsupporting

confidence: 82%

Low tortoise abundances in pine forest plantations in forest-shrubland transition areas

et al. 2017

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In the transition between Mediterranean forest and the arid subtropical shrublands of the southeastern Iberian Peninsula, humans have transformed habitat since ancient times. Understanding the role of the original mosaic landscapes in wildlife species and the effects of the current changes as pine forest plantations, performed even outside the forest ecological boundaries, are important conservation issues. We studied variation in the density of the endangered spur-thighed tortoise (Testudo graeca) in three areas that include the four most common land types within the species’ range (pine forests, natural shrubs, dryland crop fields, and abandoned crop fields). Tortoise densities were estimated using a two-stage modeling approach with line transect distance sampling. Densities in dryland crop fields, abandoned crop fields and natural shrubs were higher (>6 individuals/ha) than in pine forests (1.25 individuals/ha). We also found large variation in density in the pine forests. Recent pine plantations showed higher densities than mature pine forests where shrub and herbaceous cover was taller and thicker. We hypothesize that mature pine forest might constrain tortoise activity by acting as partial barriers to movements. This issue is relevant for management purposes given that large areas in the tortoise’s range have recently been converted to pine plantations.

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Section: Discussionsupporting

confidence: 82%

Low tortoise abundances in pine forest plantations in forest-shrubland transition areas

et al. 2017

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“…Although there is a paucity of data on population size and trends, harvest pressure appears to constitute the main threat to this species. The radiated tortoise Astrochelys radiata is currently mainly threatened from a massive increase of collecting large-bodied individuals for bushmeat and, to a lesser degree, for the illegal export of small-bodied tortoises for the international pet trade [95], [100]–[101]. The same is true for the spider tortoise Pyxis arachnoides occurring in coastal areas of south-western and southern Madagascar where habitat loss is widespread and collection occurs for the overseas pet trade [103]–[104].…”

Section: Discussionmentioning

confidence: 99%

Extinction Risks and the Conservation of Madagascar's Reptiles

et al. 2014

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BackgroundAn understanding of the conservation status of Madagascar's endemic reptile species is needed to underpin conservation planning and priority setting in this global biodiversity hotspot, and to complement existing information on the island's mammals, birds and amphibians. We report here on the first systematic assessment of the extinction risk of endemic and native non-marine Malagasy snakes, lizards, turtles and tortoises.Methodology/Principal FindingsSpecies range maps from The IUCN Red List of Threatened Species were analysed to determine patterns in the distribution of threatened reptile species. These data, in addition to information on threats, were used to identify priority areas and actions for conservation. Thirty-nine percent of the data-sufficient Malagasy reptiles in our analyses are threatened with extinction. Areas in the north, west and south-east were identified as having more threatened species than expected and are therefore conservation priorities. Habitat degradation caused by wood harvesting and non-timber crops was the most pervasive threat. The direct removal of reptiles for international trade and human consumption threatened relatively few species, but were the primary threats for tortoises. Nine threatened reptile species are endemic to recently created protected areas.Conclusions/SignificanceWith a few alarming exceptions, the threatened endemic reptiles of Madagascar occur within the national network of protected areas, including some taxa that are only found in new protected areas. Threats to these species, however, operate inside and outside protected area boundaries. This analysis has identified priority sites for reptile conservation and completes the conservation assessment of terrestrial vertebrates in Madagascar which will facilitate conservation planning, monitoring and wise-decision making. In sharp contrast with the amphibians, there is significant reptile diversity and regional endemism in the southern and western regions of Madagascar and this study highlights the importance of these arid regions to conserving the island's biodiversity.

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“…Leuteritz et al (2005) compared distance sampling with the LincolnPetersen mark recapture technique (Greenwood, 1996) and concluded that the latter method was prone to overestimation when applied to the A. radiata population in south-west Madagascar. The half-normal model that we used is known to perform well with data that show a rapid fall in detection (Newey et al, 2003;Thomas et al, 2010), as shown in Fig.…”

Section: Discussionmentioning

confidence: 99%

Status of the relict population of the Critically Endangered Madagascar spider tortoise Pyxis arachnoides

Walker

Rafeliarisoa

2012

Oryx

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The Madagascar spider tortoise Pyxis arachnoides is endemic to the coastal dry forests of south-west Madagascar. In recent years its range has been reduced by c. 71%, with the species now confined to eight fragmented populations occupying a total of 2,464 km 2 . These remaining populations are facing a significant threat of extinction because of habitat destruction and other anthropogenic pressures. We developed methodology for a line transect distance sampling survey and applied it systematically across the species' range. The resulting distance model estimated a mean density of 226.9 tortoises km −2 (95% confidence interval, CI, 168.1-306.3) and a total population of 664,980 (95% CI 492,680-897,550). Fragmentation of the species' range suggests the current population could be , 30% of the historical population. Of the remaining population 73.5% falls within protected areas. However, nine of these 12 protected areas are designated as IUCN category III, V or VI parks, allowing some extractive activities to be undertaken. The most effective strategy for the conservation of P. arachnoides would be to reduce the threats to this species and its habitat, and to develop and expand the current community-based conservation and poverty alleviation programmes in the region.

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Distribution, status, and conservation of radiated tortoises (Geochelone radiata) in Madagascar

Cited by 39 publications

References 22 publications

Low tortoise abundances in pine forest plantations in forest-shrubland transition areas

Low tortoise abundances in pine forest plantations in forest-shrubland transition areas

Extinction Risks and the Conservation of Madagascar's Reptiles

Status of the relict population of the Critically Endangered Madagascar spider tortoise Pyxis arachnoides

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