White-nose syndrome has killed millions of North American bats since its introduction in 2006, causing immense suffering and threatening the extinction of multiple species.
The welfare dimensions of white-nose syndrome are immense. The fungus infects bat skin during hibernation, causing bats to arouse from torpor prematurely, burning through winter fat reserves. Bats rouse repeatedly, becoming progressively more emaciated. They may emerge from caves in winter seeking insects that aren't there, dying from exposure and starvation. The pathological process causes skin damage and wing membrane lesions. Death from WNS is slow - involving repeated cycles of arousal, failed foraging, return to roost, and further depletion of reserves over weeks to months. The scale of suffering - millions of individual animals dying over extended periods - represents one of the most significant wildlife welfare events in modern North American history.