White-nose syndrome caused by the fungus Pseudogymnoascus destructans has killed over 90% of affected bat populations in North America, causing immense wildlife welfare harm.
White-nose syndrome causes bats to wake repeatedly from hibernation torpor, depleting fat reserves that must last through winter. Affected bats emerge prematurely during cold weather, cannot find food, and die of starvation. The welfare harm at individual level is significant — arousal from torpor is energetically costly and the animals die slowly. At population level, the scale of mortality represents one of the largest wildlife welfare crises in recorded history. Research into biocontrol treatments and probiotic applications that protect hibernating bats from infection is ongoing and represents the primary hope for population recovery.