White-nose syndrome, caused by an invasive fungal pathogen, has killed millions of North American bats since 2006, creating one of the largest wildlife welfare and conservation crises in recent memory.
White-nose syndrome causes a particularly distressing form of mortality: bats wake repeatedly during hibernation — a period when fat stores are their only energy source — and emerge prematurely in winter searching for food that does not exist. The welfare experience of starvation and cold exposure after abnormal arousal from torpor represents sustained suffering across millions of individual animals per year. The speed and scale of WNS mortality — 90%+ in some colonies — is unprecedented for a wildlife disease in North America and illustrates how a single introduced pathogen can cause welfare harm at an almost incomprehensible scale. Research into treatments is active and showing early promise, but the regulatory pathway for environmental probiotic application is slow. Meanwhile, colony monitoring networks are identifying survivors who may have genetic resistance, providing hope for population recovery.