- Frogs are going extinct. So are toads, salamanders, newts, and the intriguingly unusual caecilians. In fact, the World Conservation Union (IUCN) estimates that at least one-third of known amphibian species are threatened with extinction. While the major culprit has historically been habitat loss and degradation, many of the declines and extinctions previously referred to as "enigmatic" are now being attributed to the rapidly dispersing infectious disease chytridiomycosis, which is caused by the fungus Batrachochytrium dendrobatidis (Bd). Bd is causing population and species extinctions at an alarming rate. Can you imagine if we were about to lose one-third of the world's mammals?