Fungus Kills About 90 Percent Of Connecticut's Bats

By RINKER BUCK | The Hartford Courant
March 18, 2009

White-nose syndrome, the mysterious plague that is decimating the Northeast's bats, killed off about 90 percent of Connecticut's bats over the winter and is now galloping across the country so quickly that it threatens the nation's — and probably the world's — largest bat populations in the American South.

Jenny Dickson, the Connecticut Department of Environmental Protection wildlife biologist supervising the detection and control of white-nose syndrome in the state, said Tuesday that visits to two sample caves in Litchfield County in the past two weeks revealed veritable bat catacombs. Dickson's team of wildlife experts found thousands of dead bats floating like dead fish in standing water, or stacked on top of each other along the flat ledges of the cave walls.

"It was grim, and you don't have to be a scientist to realize the implications for the environment inside those caves," said Dickson. "This is a massive, unprecedented die-off, with significant potential impacts on nature, especially insect control."

Findings by Dickson's counterparts in nearby states paint an even more dire picture for Connecticut.

Bats are migratory, and most of Connecticut's bats fly here in the spring from hibernation caves containing hundreds of thousands of bats in the southern Adirondacks, the lower Hudson Valley, Vermont and the Berkshires of western Massachusetts. Scientists entering those caves since February have found 90 percent to 95 percent mortality rates, with some caves in New York having death rates approaching 100 percent. All told, scientists following white-nose syndrome have calculated that up to a million bats have already died in the Northeast states.

Scientists say that all bat species are vulnerable to the fungus. Dickson said Tuesday that the disease has hit hard among little brown bats and northern long-eared bats, which are the ones most commonly seen in Connecticut, but that it has spread to other species as well.

Combined with the losses of bats that hibernate in Connecticut, the deaths in neighboring states mean that bats fluttering over evening barbecues or swooping down to devour insects over cornfields will be a rare sight this summer.

The syndrome, first discovered in New York state in 2006, is a condition in which a white fungus coats the heads, legs and wings of hibernating bats. To fight the physiological effects of the fungus, bats deplete their fat reserves before the winter is over, fleeing from their caves in a desperate search for insects to eat. The ravenous, emaciated bats are then found lying in the snow or clinging to the sides of barns, and usually die before enough mosquitoes and moths hatch for them to eat.

Scientists have not been able to explain why the white fungus covering the bats, geomyces, appears in the first place, but the impact on the balance of nature is clear. Bats eat an average of more than 3,000 mosquitoes and moths apiece every night. A large die-off of the species will directly affect activities and industries that rely on natural insect control — recreation, dairy farming and horseback riding, among others.

Scientists working on white-nose syndrome say that they have detected no direct health threat to humans. But they do worry about indirect threats caused by insect-borne diseases, especially after an especially wet fall and winter that produces favorable conditions for mosquito breeding. The number of cases of such diseases as West Nile virus have been very low in Connecticut, but scientists do not know how a larger population of mosquitoes will affect human and animal health.

Dickson said that her team of scientists will be helped by public reports of bats flying in the daytime during the next two weeks, when there are not enough insects for bats to eat. The telltale white fungus on the bats will not be present, because it disappears when exposed to the sun and heat. Reports of daytime sightings, or other erratic behavior by bats, may be made to the DEP's number, 860-675-8130.

Since it was first detected in New York caves three years ago, white-nose syndrome has crossed state lines, probably carried by migrating bats themselves. Last year, the range of the plague had been restricted to the Albany, N.Y., area and western New England. But this year white-nose syndrome has been confirmed from New Hampshire to southwestern Virginia. The spread of the condition to Virginia especially concerns scientists.

Crops At Risk
Ecologist Merlin Tuttle of Texas is a bat expert and wildlife photographer who leads the battle to save the endangered gray bat.

"The number of bats that have died so far, which is probably over a million now, will be dwarfed by what is going to happen in the next few years," Tuttle said.

"Virginia is right on the border of perhaps the biggest bat hibernation areas in the world — Tennessee, Alabama and Kentucky — where there are caves with such large populations of bats we can't even measure how many millions are in there. They spread from this area across vast ranges of the agricultural South. Mortality rates like those we are seeing in the states already hit by [white-nose syndrome] would be devastating for the national bat population."

Studies conducted by Tuttle and other scientists have documented the huge value that bats deliver to farming and forestry. Every June, over the vast corn and cotton fields of Texas, for example, millions of corn earworm moths migrate north from Mexico, descending at dusk to lay their eggs on crop fields. If left unchecked, these eggs would hatch within a few weeks, and then new moths would lay additional eggs, multiplying their scourge and smothering the crops.

Using Doppler radar, radio microphones beamed into the sky and feces studies of free-tailed bats, scientists have documented that "high-altitude foraging" by the bats intercepted most of the moths before they could land on crops, saving millions of acres of cotton and corn. One study concluded that the free-tail bats — there are at least 100 million of them in central Texas — consume more than 2 million pounds of insects every night.

But this balance-of-nature act is not restricted to Texas.

"We have the same corn, the same earworm moths, the same night-feeding by our bats right here in Connecticut," said Dickson. "And now that we have this huge mortality of bats, [white-nose syndrome] could have a severe impact on our crops, but we just don't know yet."

More Need For Pesticides
One scenario that worries wildlife scientists is increased use of pesticides. If farmers see that a crop-eating insect has landed on their fields, they call in crop-dusting planes or truck-sprayers right away, which then encourages other farmers to order spraying. Without enough bats to protect crops, farmers might be tempted this year to use more pesticides, a chemical chain-reaction that can affect people, wildlife and nearby streams, Tuttle and other experts said.

Even if the cause of white-nose syndrome is identified soon, the damage to the bat population has already been substantial.

"This is a species that reproduces very slowly and that lives very long for the wildlife world — many bats survive for 30 years," Dickson said.

"Each time you lose a bat, you're losing a very precious benefit to the environment. It will take generations to replenish this bat population."

•News Information specialist Cristina Bachetti contributed to this story.

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