Many people are frightened by bats, but they really shouldn’t have any fear. Bats don’t want anything to do with us; they are, however, busy acting as an important predator of flying insects.
All animals have similar problems; they need to get something to eat, to find a partner, and a place to sleep, but recently bats have a new challenge and this is a big one. White nose bat syndrome (WNBS), named for the white fungus that grows on the noses, wings and tails of bats, has had a devastating effect on their populations.
In North America, it was first found in a New York cave in 2006 where over half the hibernating population of bats were killed. Little is known about the fungus responsible for the syndrome, only that it has resulted in severe population declines.
The fungus has spread westward, covering half of the continent. It has affected a variety of species including the Little Brown, Northern Long-eared, Big Brown, Tri-coloured, Eastern small-footed, and two endangered species – the Gray and the Indiana bat.
From 2006 to 2011, it’s been estimated that more than five million bats have died. The losses are so severe that extirpation (local extinction) to some bat species has become a real threat. The hardest hit species is the once common Little Brown bat. An American survey showed that there has been a 93 per cent decrease in the population of this bat in 23 caves in eastern North America.
How can a little fungus cause such big problems? During the winter, bats enter a hibernation state where their bodies slow down and cool in order to conserve energy. As a result, their immune systems are compromised and they become susceptible to infections such as the fungus. The fungus causes irritation and awakens bats every few days, as opposed to their normal every 10-20 day wake/sleep schedule. Every time they wake up, they use energy from their body reserve during a time when no additional food is available. If they wake up too many times during hibernation, they run out of body reserves and starve.
There are few answers to the why’s and how’s but it is thought that the fungus is an invasive species from Europe that has only recently entered the cave system of North America. In Europe the bats seemed to have evolved with the fungus and may have built up an immunity. Humans are not affected by the fungus as it requires a cold body temperature to survive. The optimal body temperature to support fungus growth is 12 -16oC.
So why do we care about our bats? Besides our innate desire to maintain general wildlife diversity, bats play a critical role in sustaining a healthy ecosystem. Bats are the number one consumer of flying insects; an individual bat can eat a thousand mosquito-sized insects every hour. A world without bats means an abundance of pesky insects and an increased dependency on pesticides in agriculture. This means higher costs of food and exposure to harmful chemicals with unknown side effects. More importantly, bats reduce the outbreak of mosquito-borne pathogens such as the West Nile Virus.
Much research is being done to understand future consequences of this fungus. In the meantime, there are a few steps we can take to minimize the spread of the fungus: Avoid caves that contain hibernating bats, paying close attention to cave closures and advisories. Cavers should decontaminate their gear before and after entering caves and mines. In the bat world, trying to save bats from WNBS is a daily fight against what may be the inevitable. The least we can do is to not help the spread.