Amphibians Decline

Amphibians — frogs, toads, salamanders, newts, and caecilians (limbless, worm-like) — are the most threatened class of vertebrates: 41% of species are threatened with extinction (compared to 25% of mammals and 13% of birds). They are particularly vulnerable because their permeable skin (which they use for gas exchange) makes them highly sensitive to pollution, climate change, UV radiation, and disease. The chytrid fungus (Batrachochytrium dendrobatidis, Bd) has caused the most spectacular extinction crisis of any disease in recorded vertebrate history — infecting amphibian skin and disrupting electrolyte absorption, it has driven 90+ species extinct and threatened 501 more. The golden toad of Costa Rica (last seen 1989) and the Panamanian golden frog (extinct in wild) are among Bd's casualties. Paradoxically, some amphibian populations appear to be developing resistance — offering hope for eventual coexistence. Poison dart frogs (Amazon) sequester toxins from their insect diet; the golden poison dart frog has enough toxin to kill 10 adult humans.