| Amphibians in danger |
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| One third to one half of all amphibian species are threatened with extinction, with probably more than 120 species already gone in recent years. This is significantly more than any other group of organisms: by comparison, 12% of bird species and 23% of mammal species are threatened. |
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| Habitat loss and degradation are the greatest threat to amphibians, affecting nearly 4,000 species. Although disease appears to be a relatively less significant threat for amphibians, for those affected, it can cause sudden and dramatic population declines resulting in very rapid extinction. In comparison, although habitat loss and degradation affect a much greater number of species, the rate at which a species declines is usually much slower, and there are a number of strategies, such as the creation of protected areas, to counter this threat. |
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| Frightening statistics |
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50% of around 6000 described amphibian species are threatened with extinction. 33% are known to be threatened and 23% are data deficient but believed to be threatened. |
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122 amphibian species (at least) are believed to have already gone extinct. |
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Threats to an estimated 500 amphibian species cannot currently be mitigated quickly enough to stave off extinction, i.e., those who require ex situ intervention. |
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Currently the global zoo community is only prepared to manage 50 amphibian species long term (extreme best-case scenario), which equates to only 10% of the amphibian species that are threatened with extinction. |
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Each of the 500 largest WAZA zoos must take responsibility for just 1 amphibian species to prevent their extinction. |
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| Amphibians as indicators of environmental health |
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| Amphibians’ thin skin help them drink and breathe, but also make them susceptible to environmental contaminants, particularly agricultural, industrial, and pharmaceutical chemicals. |
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| Amphibians have been likened to canaries in the coal mine: just as miners used sensitive canaries to warn them of toxic gases in the mines, amphibians might be warning us of unsafe environmental conditions that could eventually seriously impact our health. |
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| Amphibians are also vital components of their ecosystems. They serve as significant predators of small invertebrates, as abundant prey for larger predators, and as a vital link in the food web between the two. In areas of the world where amphibians have declined, there has been an increase in invertebrate pests that damage crops and that carry human diseases. |
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| Geography of diversity |
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| The diversity map clearly shows certain areas of high global diversity, including tropical South America and tropical West Africa. The problem of uneven survey efforts around the world, however, complicates interpretation of the map. Regions such as Indonesia, New Guinea and the Congo Basin are especially likely to be underrepresented due to lack of adequate surveys. |
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| From a country perspective, Brazil, with at least 751 species, has the greatest number of amphibians of any country on Earth, followed closely by Columbia. |
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| Among the Old World countries, the level of survey effort is often much lower than in the Americas. Indonesia is predicted to be the richest country in terms of amphibian diversity outside the Americas, but it is doubtful if even half of its species are yet known. |
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| Geography of threatened species |
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Source: the Global Amphibian Assessment.( http://www.globalamphibian.org ) |
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| The global distribution of threatened amphibians is very different from depictions of overall species diversity. The greatest concentration of such species – including well over half of the currently known threatened amphibians – is in a relatively limited area running from southern Mexico to Ecuador and Venezuela, and in the Greater Antilles. This region is dominated by species with small ranges, often living in montane areas. Many of these species have been subjected to severe habitat loss, and exposure to the fungal disease chytridiomycosis. |
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| Other important concentrations of threatened species are in the Atlantic Forests of Southern Brazil, the Upper Guinea forests of western Africa, the forest of western Cameroon and eastern Nigeria, the Albertine Rift of central Africa, the Eastern Arc Mountains of Tanzania, Madagascar, the Western Ghats of India, Sri Lanka, central and southern China, Borneo, the Philippines and eastern Australia. |
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| Chytrid fungus |
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| Chytrid fungi were once thought to be predominantly free-living Saprophytes, with a few species capable of infecting only invertebrates and vascular plants. In 1998, a new species – Batrachochytrium dendrobatidis (hereafter Bd) – was described infecting amphibians. Bd has now been identified in association with amphibian die-offs on every amphibian-inhabited continent. From the site of its introduction, it generally spreads in a wave-like fashion at 28-100km/yr, often destroying entire amphibian communities as it goes. Where it thrives (generally cooler riparian habitats), 50% of species and 80% of individuals can be expected to disappear within 1 year. It cannot be stopped in the wild, and it persists for an unknown period of time even after the amphibians disappear. A few species seem able to live with it as adults, likely serving as reservoirs and vectors for future outbreaks. |
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| Chytrid fungi were once thought to be predominantly free-living Saprophytes, with a few species capable of infecting only invertebrates and vascular plants. In 1998, a new species – Batrachochytrium dendrobatidis (hereafter Bd) – was described infecting amphibians. Bd has now been identified in association with amphibian die-offs on every amphibian-inhabited continent. From the site of its introduction, it generally spreads in a wave-like fashion at 28-100km/yr, often destroying entire amphibian communities as it goes. Where it thrives (generally cooler riparian habitats), 50% of species and 80% of individuals can be expected to disappear within 1 year. It cannot be stopped in the wild, and it persists for an unknown period of time even after the amphibians disappear. A few species seem able to live with it as adults, likely serving as reservoirs and vectors for future outbreaks. |
Chytrid fungus swapping on captive colonies. Photo: Gerardo Garcia |
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| European Amphibians |
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| In Europe, not many amphibian species are classified as being highly endangered. Although this may be true for species when regarded over their entire range, it certainly is not true for many local populations. |
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| For Europe, ten species have been priortised: |
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Olm, Proteus anguinus spp. (2 subspp) Proteus anguinus anguinus & Proteus anguinus parkelj |
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Albanian water frog, Rana shqiperica |
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Mallorcan midwife toad, Alytes muletensis |
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Taurus frog, Rana holtzi |
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Sardinian salamanders, Speleomantes supramontis (Supramonte cave salamander) & Euproctus platycephalus (Sardinian brook salamander) |
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Betic midwife toad, Alytes dickhilleni |
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Pyrenean frog, Rana pyrencaica |
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| One species, the Mallorcan midwife toad, is already well established in AArk-type populations in captivity with extensive research and conservation initiatives. There are now plans to establish AArk-type colonies for 7 further species. So far, no progress has been made for the remaining 2 species (Olm and Pyrenean frog). |
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| Amphibians in European zoos |
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| Many of the larger European zoos have a tradition of maintaining smaller or larger collections of frogs or salamanders, often in a separate Amphibian Section, usually as part of a traditional Reptile House. Generally speaking, zoos nowadays keep a selection of Amphibians which are easily available, well visible for the public, and which are often spectacular, either by their large size or their colours. Probably, for those same reasons, the number of salamanders kept in the European zoo community is considerably lower than that of frogs: salamanders are usually even less visible and often more difficult to keep under the normal circumstances of a traditional Reptile House. |
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| With a few exceptions, not many zoos have truly focussed on the reproduction of Amphibians, or on maintaining managed captive populations. This is mirrored by the fact that there are only two EAZA Amphibian programmes in place to date, both studbooks: for the Blue poison dart frog Dendrobates azureus and for the Mountain chicken frog Leptodactylus fallax. |
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| Hopefully, now that the Amphibian crisis has become more and more familiar to the European Zoo Community, ex situ conservation efforts and the number of zoos involved in captive breeding programmes for Amphibians will greatly increase |
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| Conservation success stories |
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| Mallorcan Midwife Toad |
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| The conservation programme for the Mallorcan midwife toad (Alytes muletensis) has resulted in this species being the only amphibian species in the recent global amphibian assessment to be down listed from ‘critically endangered’ to ‘vulnerable’. This has been achieved through some 25 years of collaborative conservation work following the discovery of an extant population in Mallorca in the late 1970’s. Toads are now known from 33 sites in the Serra da Tramuntana Mountains, of which about 10 stem from reintroductions of captive bred animals. |
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| However, in late 2005 two wild populations tested positive for chytrid infection. Durrell currently holds the only chytrid free Assurance Population and is about to set up a coordinated breeding programme with other European collections. Durrell is also working to develop protocols to treat chytrid infections in the Mallorcan midwife toad. These studies will help protect infected wild populations. |
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Mallorcan midwife toad (Alytes muletensis) |
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| Jersey Agile Frogs |
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| Jersey agile frogs (Rana dalminatina) are one of only three amphibian species native to Jersey, and Jersey is the only place in the British Isles where this frog species occurs. Unfortunately its population on Jersey has been declining, and its range on the island is decreasing primarily due to pollution of breeding ponds and habitat loss. |
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| The Agile Frog Group (AFG) was formed in 1993, when the catastrophic decline of the frog came to light. Its members include staff from the States of Jersey, University, local naturalist society and Durrell. Intensive habitat management and protection, regular monitoring programme of the wild populations was supported by research on the ecology of the species in the island. |
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| Durrell is heavily involved in conservation efforts for this species on the island on a long committed project of reinforcement of the wild populations via initially a captive breeding programme. |
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Jersey agile frogs (Rana dalminatina) |
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| Mountain Chicken Frog |
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| Mountain chicken frog (Leptodactylus fallax) is the largest endemic amphibian in the Caribbean. Once ranging over seven Caribbean Islands it is now confined to the two islands of Montserrat and Dominica. A combination of hunting, introduced predators and habitat loss are thought to be the causes of the species vanishing more than 500 years ago. Being a national dish of the islands it is still hunted in large numbers. |
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| Captive colonies continue having a key role in the conservation of the species, not only as a safety net. Applied research programmes on non intrusive techniques to mark individuals, testing the implant of individual radio transponders and soft treatments against the chytrid fungus are some of the new lines of research. Future plans are to test the possibility of reintroducing the species to safe areas of their natural distribution. |
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Mountain chicken frog (Leptodactylus fallax) |
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| Edge Amphibians |
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| ZSL’s EDGE of existence programme focuses on species that are Evolutionarily Distinct and Globally Endangered. The EDGE team have recently completed the list of top 100 EDGE amphibians – the most extroadinary amphibians that are globally threatened with extinction. Alarmingly, only 15% of these species are currently receiving active conservation attention. The EDGE programme aims to raise awareness of these species and develop conservation strategies for those species that are not currently being protected. To find out more about EDGE amphibians click here or go to the EDGE homepage. |
