Salamanders are experiencing the fastest mass extinction of any vertebrate group, driven largely by Batrachochytrium salamandrivorans (Bsal) fungus, with welfare implications for billions of individuals.
Bsal infection causes salamanders to develop skin lesions from the fungal digestion of their skin. Salamanders breathe significantly through their skin, making this infection functionally equivalent to a respiratory disease. The skin ulceration from fungal growth causes pain and eventually death from electrolyte imbalance when the skin's osmoregulatory function is destroyed. The rapid population collapses observed - 96% decline in months - represent billions of individual animals dying from fungal infection. Whether salamanders experience suffering in morally significant ways is uncertain, but the scale of mortality from a disease that causes skin destruction is immense. The threat to North American populations, which have no exposure history, represents an unprecedented potential welfare catastrophe for one of Earth's most diverse vertebrate groups.