Tiny bones cover the floor of a cave in Dorset, Vermont. Bat skulls, dozens of them, scattered like dry debris across the rock. Biologists who first walked through after white-nose syndrome took hold described the ground outside as carpeted with dead bodies. The cave once held somewhere between 300,000 and 350,000 bats in winter. Today, estimates put the number at around 70,000 to 90,000. The bats continue to perish.
White-nose syndrome arrived in North America in 2006 — specifically in an upstate New York cave, just a short distance from that Vermont colony. The culprit is a fungus called Pseudogymnoascus destructans, which appears to have hitchhiked from Europe, where bats have lived alongside it long enough to develop some tolerance. American bats had no such history with it. The fungus grows as white fuzz on hibernating bats’ noses and wings, waking them mid-winter, sending them into freezing air in search of food that doesn’t exist in January. They starve. They freeze. A colony can be gone in five years. In Montana’s Azure Cave — historically home to nearly 1,900 hibernating bats — researchers returned one spring to find around 30 or 40 animals clinging to the walls. The rest were dead.
| Field | Details |
|---|---|
| Disease Name | White-Nose Syndrome (WNS) — fungal disease affecting hibernating bats |
| Causative Fungus | Pseudogymnoascus destructans (P. destructans) — originated in Europe |
| First Detected in North America | 2006 — upstate New York cave, near Dorset, Vermont bat colony |
| How It Kills | Wakes bats from hibernation mid-winter; they fly into cold air seeking food and die of exposure or starvation |
| Spread Rate | Approximately 200 miles per year westward; now reaching Montana and western states |
| Bat Mortality Rate | 90% or more of bat populations wiped out in heavily affected areas of North America |
| Colony Time to Extinction | P. destructans can extinguish an entire bat colony in as little as five years |
| Key Researcher | Eyal Frank — Assistant Professor, University of Chicago; published findings in Science, September 2024 |
| Pesticide Increase Recorded | Farmers in affected counties increased insecticide use by an average of 31.1% after bat die-offs |
Given its scope, it’s difficult to ignore how little attention this has gotten. According to the majority of scientific reports, this is among the worst outbreaks of wildlife diseases in recent memory. As of right now, it has been confirmed that the fungus is spreading westward at a rate of about 200 miles per year throughout Alaska, Arizona, Florida, Hawaii, and the majority of the continent. However, it hardly registers for the majority of people. Animals that are charismatic are not bats. They don’t work well as conservation campaign mascots. Most of us make a special effort not to think about them, but they live in caves and emerge at night.
A 2024 study by University of Chicago economist Eyal Frank, published in Science, made the cost of that indifference startlingly clear. Bats eat insects — a lot of them. A single little brown bat consumes more than 40 percent of its body weight in bugs on a good night, including the kind of crop pests that farmers spend significant money trying to control. When the bats disappeared from infected counties, farmers compensated by increasing pesticide use — by 31.1 percent on average. Frank then looked at infant mortality in those same counties and found death rates running 7.9 percent higher than in areas where bat populations were still intact. That works out to an estimated 1,334 additional infant deaths. The pesticide use was within regulatory limits. Apparently, it was still sufficient.
What makes this study genuinely unusual — and what gives it more weight than a typical correlation paper — is that the spread of white-nose syndrome functioned almost like a natural experiment. Researchers had a unique opportunity to compare otherwise similar groups because the fungus spread erratically, affecting some counties before others without any discernible social or economic pattern. Charles Taylor of the Harvard Kennedy School said, “The bat disease wasn’t expected, and it shouldn’t have preferentially targeted certain groups over others.” In environmental health research, such a clear comparison is uncommon and makes the results more difficult to discount.
I can’t help but think of a parallel. An estimated 500,000 people died in India as a result of the decline in vulture populations, which was brought on by a veterinary medication that proved to be fatal to the birds. As a result, rotting carcasses went unconsumed and rabies spread. The structure is the same, but the mechanism is different: when one species is removed from a functioning system, the effects spread in unexpected ways. This pattern may persist because we continue to view ecosystems as collections of discrete components rather than as systems in which everything is interconnected.
One pup is produced annually by the small brown bat females that survive in Dorset. Of those puppies, only roughly two-thirds survive the first twelve months. Even in areas where the bats are surviving, recovery will take decades. It is still genuinely unclear if there will be sufficient time and political will to finance the necessary monitoring and intervention.
