Endangered Species Handbook

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It's Too Late

Amphibian Extinctions

     Six species of amphibians ‒ all frogs ‒ are known to have become extinct since 1500.  No recorded amphibian extinctions have taken place on islands, despite the large number of endemic amphibians native to large islands such as Madagascar, New Zealand, Cuba and Puerto Rico.  Many of these, however, now face this threat.  Yet it is likely that amphibian extinctions occurred as a result of the draining of wetlands or due to their use in growing rice following the colonization of the latter islands by native peoples thousands of years ago.  The extinct frogs were mainland species, and all disappeared during the 20th century.  The Israel painted frog (Discoglossus nigriventer) became extinct around 1940, when Lake Huleh, its sole habitat, was drained for agriculture.  The Vegas Valley leopard frog (Rana fisheri) disappeared in 1960 when its desert spring habitat was destroyed by groundwater pumping for agriculture.  Two Mexican frogs endemic to wetlands north of Mexico City died out by 1979 after their wetlands were drained for the construction of homes.  The best known extinction in recent times is that of the beautiful golden toad (Bufo periglenes), which is acknowledged by most experts to have disappeared from its rainforest home on a Costa Rican mountain in the late 1980s.  This species had been featured in National Geographic Society films and articles, and was also the subject of a research study when it suddenly died out. 
 
     A large number of frogs ‒ at least 20 species ‒ have not been seen for many years, and many may soon be declared extinct.  Some of these are among the most unusual examples of evolution on Earth.  In a few pristine areas, frogs have mysteriously vanished.  An Ecuadorian biologist reported in the 1990s that a dozen species he had been studying in a high altitude meadow disappeared without a trace.  Experts are in disagreement over the causes of the vanishing of so many frog species.  Many species are believed to be victims of ozone depletion, which increases the amount of ultraviolet radiation reaching the Earth, destroying frog eggs and often adult frogs as well.  Other scientists believe frogs are disappearing from a combination of causes, including disease possibly induced by an immune system lowered by pollutants, pesticides and habitat destruction. 


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