Bats are unwitting participants in a disturbing vanishing act
A strange fungus called white nose syndrome is wiping out little brown bat colonies across North America. The declining bat population has serious consequences for humans.
The mysterious, nocturnal habits of bats have led to demonization of this unique animal. Now, as a strange disease called white nose syndrome quickly wipes out bat colonies across our continent, we’re beginning to appreciate how important bats are to our agricultural system—and possibly our health. But is it too late to help the little brown bat?
Bees have snagged much of our appreciation when it comes to the impact of animals on our food security; however, bats are just as worthy of our respect and praise. Bats are hugely important in reducing pest-related damage to many crops, and some species are even important pollinators of fruit.
However, a strange fungus causing a disease known as white-nose syndrome (WNS) is rapidly wiping out hibernating bat populations around the continent, resulting in profound implications for all of us.
A one-way ticket to extinction
White-nose syndrome was first detected in 2006 in a cave in New York, and has since spread across 19 states and into Canada, where it has been identified in bat populations in Nova Scotia, New Brunswick, Quebec, and Ontario.
The fungus that causes this syndrome, known as Geomyces destructans, appears to affect at least nine species of cave-hibernating bats, including little brown bat, northern long-eared bat, and eastern small-footed bat.
To date, at least 5.5 million and upward of 6.7 million bats have died; little brown bat—the most common species in North America—has been the hardest hit.
White-nose syndrome, so-called because of the appearance of a white “fuzz” on the noses of infected bats, has a very high mortality rate—anywhere from 75 to 100 percent—and appears to affect bats by causing them to awaken too early from hibernation. Once awake, bats quickly consume their bodily fat reserves and ultimately die of starvation and exposure.
This past winter the fungus was responsible for wiping out New Brunswick’s largest population of hibernating bats, and scientists are predicting the little brown bat will become locally extinct in northeastern Canada and the US within 15 years, with potential for complete extinction across North America if the fungus continues to spread westward.
Research indicates the fungus is an invasive species from Europe; however, so far bat populations in Europe seem unaffected by the fungus. Why this seems to be the case is uncertain, but scientists in the UK are closely following the plight of bats in North America in an effort to understand and mitigate any problems that may arise in the future.
Impact on Canadians
To date there has been no evidence to suggest the fungus that causes WNS in bats poses direct risk to human safety. However, as bats are voracious consumers of insects, including mosquitoes and agricultural pests, the loss of little brown bat to WNS is expected to have significant agricultural, economic, and health implications for Canadians.
Bats save North American farmers billions of dollars a year in insect-control costs by consuming pests of various crops. For instance, codling moth damage to pears was significantly reduced if the orchard was located near a known bat roosting area. With reduction and potential loss of bat populations across North America, farmers will need to increase chemical input to control various pest populations.
As conventional farmers spend more on pesticides to keep pest levels down, the cost of the chemicals will be shifted on to consumers, resulting in higher food prices, possibly increased chemical residue in our food and water, and larger environmental problems associated with greater pesticide use.
Organic farming and integrated pest management
Bats are considered one of the greatest allies to organic farmers. Given their importance in agricultural pest reduction, the impact of an increased pest load caused by little brown bat’s extinction and reduction of other bat populations will profoundly affect organic farmers, who often rely on bats as part of a natural integrated pest management system.
Although under lab conditions an individual bat can eat 600 mosquitoes per hour, evidence suggests that in the wild they are opportunistic feeders, preferring larger insects. Scientists have yet to reach consensus on whether bats make a significant contribution in reducing mosquito numbers, but little brown bat appears to be one of the most avid mosquito-eaters, being able to eat twice as many mosquitoes per hour as other bats.
Despite its preference for larger insects, a single little brown bat will still eat over a thousand mosquitoes on any given night, including mosquitoes carrying viruses that cause West Nile and eastern equine encephalitis.
Loss of little brown bat could mean increased instances of mosquito- and other insect-borne illnesses; in fact, some medical establishments in the US are already advising the public to be vigilant about mosquito bites in areas where WNS is present in the bat population.
Furthermore, climate change is expected to increase the range of many disease-causing mosquitoes and insects into Canada and, combined with loss of bats, could have increasingly negative consequences for the health of Canadians.
Batting for the bats
Bats need all the help they can get. Unfortunately, many unfounded fears about bats prevent people from reaching out to this extraordinary mammal. However, even if you don’t want to get too close, there are a few things you can do to get involved.
Bats moving in
If bats have moved into your home, hire professionals to humanely relocate the bats. These “urbanized” bats may be among our last hope of saving some bat species from extinction, as urban bats have so far been unaffected by WNS.
The most likely reason for this is that the places urban bats choose to roost in—dry, warm attics and walls of homes—are not conducive to growth of the fungus that causes WNS, which flourishes in the cold, damp caves and mines in which rural bats hibernate.
However, take care to remember bats should always be handled with caution and by experts only—although very rare, bats can carry rabies and potentially infect humans.
To help encourage bats to stay out of your home, hang up bat houses on your property. Bat houses can easily be built by hand or ordered online, and once bats have established themselves in their new roost you may appreciate their efforts at keeping your barbecue parties mosquito free.
Bats behaving strangely
If you see bats acting strangely—such as bats flying around in the daytime or during the winter months—report the sighting to your local environment ministry. Such activity could mean the bat is unwell, and is part of a roosting colony that has WNS.
Catching new instances of WNS early on before it has a chance to spread to neighbouring bat populations could help stave off continent-wide extinction of certain bat populations.
Prognosis for many of our bat species, and little brown bat especially, is not good. However, if we work to help the ones that are left and prevent the spread of white-nose syndrome, we may be able to create some hope for this important mammal’s future—and ultimately, the future of our food security as well.