Bats: Insects for dinner
Dig in with the Master Gardeners
When you mention bats, many people have an instant reaction and it’s not often a positive one. Our culture is rich with bat imagery and every October we can immerse ourselves in spine tingling spookiness or dark and mysterious festivities. Either way, bats play a key role at Halloween. And how many of us went camping as kids and tried to scare each other after dark by ruffling each other’s hair and saying it was a bat? That was always good for a scream! The truth is that bats in North America only eat insects, and unless you actually throw one at that weird kid, they never get tangled in anyone’s hair. In fact, bats are a profoundly important part of our natural environment.
There are currently 1,116 bat species identified worldwide, with the majority of them living in tropical regions. Of these, only 44 species live in the U.S. and Canada. They range in size from 0.07 ounces with a wing span of about 4 inches, to more than 2 pounds with a wing span of almost 6 feet. All of these North American bats hibernate in the winter and give birth only once every spring to a litter of only one or two offspring. Female bats suckle their young with milk for about four to six weeks.
Bats in North America are pollinators and voracious consumers of mosquitoes and insect pests. According to Boston University’s Kunz Bat Lab, a single bat will eat up to one half of its body weight in insects in one balmy night. The lab extrapolated this data to the population of bats living in a 100-mile area of New England. Using the conservative number of 50,000 bats they calculated that over 13 tons of insects are consumed in one summer! That is 13 tons of nocturnal insects, including many crop and forest pests. Now try to imagine how much pesticide would be needed to do that job for ourselves.
Here is the bad news. Our bat populations in North America are facing two new and serious threats: White-Nose syndrome, and the increased development of wind-power facilities. Both of these threats are described in detail in the April edition of the journal SCIENCE (“Economic Importance of Bats in Agriculture” Vol. 332). This article was summarized and discussed in May’s Ohio Country Journal.
White-Nose syndrome was first detected in New York State in 2006. It is a fungal skin infection that attacks while the bats are hibernating in caves. It kills 90–100 percent of bats in infected colonies over two or three seasons. WNS is estimated to have killed more than one million bats in the northeastern U.S. to date. Both Ohio and Kentucky announced this spring that the disease had arrived, bringing the total affected area to 16 states and three Canadian Provinces.
This rapidly spreading disease is expected to cause billions of dollars in losses to North American agriculture in the coming years. Data from the SCIENCE article was extrapolated to show that the estimated losses for Ohio would be expected to range from $740 million up to approximately $1.7 billion per year. However, as the OSU Extension/Delaware County points out, most of the data came from Texas and was applied to cotton crops. Ohio’s corn and soybean crops have not been studied.
The current data considers crop acreage, the number of crop pests eaten by bats, the damage to crops that is prevented by the bats, and the resulting need for farmers to spend less on pesticides. Until specific combinations of crop varieties and bat species are examined, it is impossible to determine if any noticeable impact will be felt in Ohio.
As for the problems caused by wind turbines, there are currently no continent-wide monitoring programs that track wildlife fatalities at these sites so the numbers of migratory bats being killed is difficult to assess. However, significant numbers of several bat species are being found dead and attention is now focusing on finding out why.
Thriving bat populations are so important to the Earth’s ecology that U.S. and international agricultural agencies are now working together to find solutions to the most urgent threats. Right now the best we can do as individuals is to appreciate our bats and practice mindful gardening.
Karen Zinck is an OSU Extension Delaware County Master Gardener Volunteer.