Understanding White-nose Syndrome: A Threat to Bat Populations

Learn about White-nose Syndrome, the devastating fungal disease rapidly depleting North American bat populations.

By Garret Merkley · Explainer · Jun 4, 2026

Branched from The Essential Role of Bats in Southeast Ecosystems and Insect Control

Quick take

White-nose Syndrome (WNS) is a deadly fungal disease affecting hibernating bats.
It's caused by the cold-loving fungus *Pseudogymnoascus destructans* (Pd), which irritates bats and causes them to wake too frequently during hibernation.
Frequent waking leads to bats burning through their fat reserves, causing starvation, dehydration, and eventual death.
WNS has killed millions of bats across North America, profoundly impacting ecosystems and insect control.

White-nose Syndrome (WNS) is a serious and often fatal disease primarily affecting hibernating bats in North America. It's caused by a cold-loving fungus that grows on bats' exposed skin, particularly around their muzzles, wings, and ears, leading to characteristic white fuzzy growths.

How the Fungus Attacks Hibernating Bats

The culprit behind WNS is a fungus called *Pseudogymnoascus destructans*, or Pd for short. This fungus thrives in cold, damp environments, precisely the conditions found in caves and mines where bats hibernate. When bats enter hibernation, their body temperature drops significantly, and their immune system becomes less active. This makes them vulnerable to Pd.

As Pd grows on a bat's skin, it causes irritation and damage. Bats are naturally sensitive creatures, and this irritation leads them to wake up more often than they should during their long winter sleep. Each time a bat rouses from hibernation, it uses a considerable amount of energy, burning through the precious fat reserves they need to survive until spring. This repeated disturbance results in starvation, dehydration, and often, death.

The Cascade of Impact on Bat Health

The signs of WNS are often visible: white fungal growth on the muzzle, wings, or ears. Beyond the visible symptoms, the disease disrupts the bats' critical physiological processes during hibernation. The wing membranes, essential for flight and regulating body temperature and water balance, become damaged, further exacerbating dehydration and making successful foraging difficult even if a bat survives until spring. The cumulative effect of energy depletion, dehydration, and tissue damage is devastating, leading to extremely high mortality rates in affected colonies, sometimes reaching 90-100%.

WNS matters immensely because bats play a crucial role in our ecosystems. They are primary predators of night-flying insects, including many agricultural pests. The loss of millions of bats due to WNS has significant ecological and economic consequences, potentially leading to increased insect populations, greater reliance on pesticides, and disruptions to food webs. The disease continues to spread across North America, posing an ongoing threat to bat species and the health of our natural environments. Understanding and addressing WNS is vital for protecting these invaluable nocturnal allies.

Can White-nose Syndrome harm humans or other animals?

No, White-nose Syndrome is not known to affect humans, pets, or livestock. It specifically targets bats, thriving in the cold body temperatures bats maintain during hibernation.

What bat species are most affected by WNS?

Several bat species are highly susceptible to WNS, including the little brown bat, northern long-eared bat, tricolored bat, and Indiana bat. Some of these species have seen drastic population declines of over 90%.

Is there a cure or treatment for White-nose Syndrome?

Currently, there is no widespread cure for WNS in wild bat populations. Researchers are exploring various strategies, including antifungal treatments, probiotics, and vaccines, but these are still in experimental stages and challenging to implement on a large scale in natural hibernacula.

What can be done to help prevent the spread of WNS?

You can help by staying out of caves and mines where bats hibernate to avoid inadvertently spreading the fungus. If you must enter such sites, always follow decontamination protocols for clothing and gear. Supporting bat conservation efforts and reporting sick or dead bats to local wildlife authorities also makes a difference.

How does WNS impact agriculture?

Bats consume vast quantities of insects, many of which are agricultural pests. With fewer bats due to WNS, farmers may face increased crop damage from insects, potentially leading to higher costs for pest control and reduced crop yields.

Sources

USGS National Wildlife Health Center (NWHC)
White-nose Syndrome Response Team