The little brown bat, shown here, is among the many bat species being ravaged by a fungal disease. Getty Images
- Habitat loss, climate change and pesticide use may be putting bats, bees and frogs at greater risk for diseases.
- Fungal diseases affecting bats and frogs eat through their skin, sometimes even replacing it.
- Conservationists are trying to create safe, man-made habitats for the animals.
In recent years, diseases have ravaged through bat, honeybee and amphibian populations, and now animal experts suspect that shared factors may link the deaths, which are putting many species at risk for extinction.
The latest setback affects bats, given this week's announcement that the deadly fungal disease known as white-nose syndrome has been confirmed in already endangered gray bats. The illness, caused by the fungus Geomyces destructans, has mortality rates reaching up to 100 percent at some sites.
Simultaneously, Colony Collapse Disorder continues to kill honeybees, while yet another fungus, Batrachochytrium dendrobatidis, has wiped out more than 200 frog species across the world.
"It appears that many species are under an immense amount of stress, allowing opportunistic diseases to take hold," Rob Mies, executive director of the Organization for Bat Conservation, told Discovery News. "Life is far more complex, so a single cause is likely not the only explanation for the bat, bee and frog deaths. There could be five, six or more factors involved."
One is how humans may be helping fungal spread. According to the U.S. Fish & Wildlife Service, white-nose syndrome can be inadvertently transferred from people to bats.
"Some of the first caves in North America to be affected by white nose syndrome were in very high tourism areas," Mies said. "Somebody could have visited a cave in Europe wearing boots, and then brought back a tiny bit of mud on the boots containing dormant fungus."
He explained that the fungus, which is sensitive to body warmth, does not infect humans and most other animals. Bats experience a lower body temperature while hibernating, when the fungus can set in.
"It may eat into a bat's skin, even putting holes in it," Mies said. "The fungus can grow to a point where it winds up replacing the skin."
The amphibian fungus also attacks through the skin, causing an infected frog's skin to become up to 40 times thicker than usual, according to San Francisco State University biologist Vance Vredenburg, who recently conducted a study on the related disease, known as chytrid. Since frogs use their skin to absorb water and vital salts, such sodium and potassium, infection often leads to death.
Other human factors tied to the bat, frog and bee deaths include the use of chemical pesticides that may be absorbed through the skin, climate change, habitat loss and the spread of other health threats, such as viruses and mites.
Helene Marshall of Marshall's Farm Natural Honey told Discovery News that "the virus causing CCD came to us when U.S. beekeepers were importing Australian packaged bees to meet the high pollination demand of the almond growers here in California."
Both bees and bats are critical to agriculture. Bats, like bees, can help to pollinate. They are also a primary predator of agricultural and other insect pests, such as mosquitoes. Frogs additionally consume insect pests.
The U.S. Fish & Wildlife Service now has a national plan for managing white-nose syndrome in bats. It allows for diagnostics, disease management, disease surveillance and more. But Mies points out that for animals like bats and frogs, antifungals can be "pretty nasty medicines," doing damage of their own and perhaps further damaging ecosystems.
He said that man-made antifungal-treated mines might be created in the future so that bats ready for hibernation can use them. For bees, Marshall has partnered with hotels, businesses and individuals to establish more carefully monitored honeybee hives.
Bees, frogs and bats are usually not poster species for animal conservation, so educating people about their benefits to the environment and economy (via agriculture) is important. Bats are particularly maligned.
"Humans are still killing bats," Mies said. "If one finds its way into your home, please humanely evict it. If possible, you can also put up bat houses, providing much needed safe habitat for them."