Arguably one of the worst wildlife diseases of our time, white-nose syndrome (WNS) has killed millions of bats in North America. An estimated 6.7 million bats have succumbed to the disease since 2006. The disease is so tenacious that once introduced into a hibernaculum (a refuge used during the winter), 70 to 100% of the hibernating bats will perish. First found in New York, WNS has now spread to most of the eastern U.S. with a case in Washington that has been the westernmost discovery. But, recent research has revealed a silver lining to this aggressive and seemingly hopeless outcome.
Contrary to popular beliefs and myth, bats are not to be feared. Bats are extremely important to maintaining a healthy environment and provide us with pollination benefits, pest control, and insect management. While they do have small eyes, bats are not blind and can actually see just fine. Because most of their feeding/hunting is done at nighttime, echolocation is a better navigation tool than eyesight, hence the blind bat theory. Going along with that, it is often said that bats will swarm your head and get tangled in your hair—also not true. When taking flight, a bat will tend to drop down directly from their roost and flap their wings before they start to lift off. This may be where the “swooping down” and “nesting in your hair” myth began. Like all other wild animals, bats do not purposefully want to be near us. They view humans as an unknown threat and would much rather steer clear. And lastly, bats are not the disease-ridden monsters that some have made them out to be. While all mammals can contract and carry rabies, only about 5% of wild bats that have been tested for rabies proved positive. In fact, 0-2 deaths per year can be attributed to bat rabies in the United States, and 99% of the deaths from rabies in the United States come from contact with rabid dogs or cats.
There are more than 1,300 bat species worldwide, about 50 of which reside in the United States. Bat species are broken up into two main groups: micro and megabats. Megabats are generally larger, fruit-eating bats whereas microbats are smaller and feed on insects, fish, lizards, birds, etc. Most of the world’s bats are microbats, living worldwide except for Arctic regions. So far, WNS seems to only affect bats that hibernate throughout the winter. These bats are most vulnerable and roost in close proximity to other bats, making for easy transmission. This fungal disease attacks the bare skin of bats while they are hibernating and can be spread through bat-to-bat contact and transmission of spores by humans on clothing, shoes, or equipment. Pollinating and migratory species do not seem to be affected. Many hibernating bats roost inside caves, where the atmosphere is perfect for cultivating a cold, dark, and damp loving fungus. As the fungus infects a healthy bat, it creates discomfort such as agitation and itching, oftentimes around a bat’s face or nose. This awakens the bat and causes them to burn critical fat reserves for surviving the winter. With no available food or water and wasted reserves, the bats will eventually die. WNS can also cause massive destruction to their very thin and fragile wing tissues, limiting or preventing mobility.
Scientists have been experimenting with a multitude of combat methods, from UV light tunnels, to vaccines, to biological control methods such as fungus that will fight off the WNS fungus. In 2015 there was a promising study that had successfully treated and released 75 once-infected bats back into the wild of Missouri. Using a bacterium that is naturally released by bananas, researchers were able to harness anti-fungal properties and stop the spread of WNS. However, impacts the bacterium could have on other native organisms is precariously unknown, and while humans have been working towards a solution, so has nature! Scientists have found that bats infected with WNS express an immune response and actively try fighting off the fungus themselves. This response is hopeful, but it’s still too early to determine how effective. Some small populations of bats in New York (where the disease was initially found) are believed to be developing a resistance to the disease. Thermal cameras in Virginia have also recorded adaptations being made by the Indiana bat, including waking up as a group nightly during hibernation to limit fungal spread with group warmth and conserve energy use.
As for the bats that are less likely to get WNS due to their different behaviors (tree roosters, pollinators, migraters, etc.), they have begun to aid in their infected counterparts’ workload. Where niches have opened up, these “resistant” species have moved and started to feed on the abundance of pests and insects that are not being controlled as they normally would. From the public to scientists to fellow bat species, it seems as if everyone is doing their part in comBATing this devastating disease.
What other wildlife diseases are prevalent in your area?
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