Bats are genuinely weird creatures, revered and feared throughout human history. The ancient Egyptians hung bats over the doorway to prevent the entry of diseases.
In Africa, bats were often associated with voodoo. In China, they meant good fortune and happiness. And in modern America, they’re usually recognized as voracious eaters of insects and occasionally the carriers of rabies. Though they’re usually greeted with curiosity while chasing insects at dusk, most people are loath to touch or handle them. But they’re in trouble and they definitely merit our concern and help.
There are more than 900 species of bats worldwide. And to set the image straight, only three are vampires. At least 18 species are known in Utah. Discussion of those can be found online at dwrcdc.nr.utah/gov/ucdc/viewreports/bats.pdf. Published in 2000 by the state Division of Wildlife Resources, the report gives a solid review of what is known about each Utah species. Sadly, there are major gaps in our knowledge.
But our focus today deals mainly with bats across our nation. They face two major threats to their health: a disease apparently caused by a previously unknown fungus and called white-nose syndrome, and the wind turbines we are erecting for electrical power generation.
White-nose syndrome was first detected in February of 2006 near Albany, N.Y., and has decimated numerous populations of bats in the New England area.
It is known to attack at least six different species and is estimated so far to have killed more than a million bats. Whether it will move further west is presently unknown, but once it infects a hibernaculum (hibernation area such as in caves or mine shafts), it causes between 90 and 100 percent mortality.
Data on the mortality from wind turbines are hard to come by. It appears that migratory species of tree-dwelling bats are, for some reason, the most susceptible to hitting the turbines. And mortality of those species is known to be high. But … why really should we care?
There are several concerns. First may be that the more mosquitoes they eat, the fewer bites we humans get and the less chance there is for transmission of mosquito-borne diseases such as West Nile virus. More critical is that bats have huge economic benefits for agriculture, and that means your and my food. The April 1 issue of the journal Science reviews the problems ahead.
As with the Utah data, data for bats’ contributions to the nation as a whole are not precise. But estimates with plausible credibility can be made. It seems, for instance, that the loss of bats in areas presently affected with white-nose syndrome means that there are between 725 and 1,450 tons of insects flying about each year that would have been devoured by the missing bats. That’s a lot of skeeters, gnats and midges, among other delightful creatures!
The Science article estimates that bats are worth roughly $22.9 billion annually to American agriculture. While that figure includes the direct comparative costs of pesticides with and without bats, it does not include the “downstream” impacts of the pesticides on ecosystems. It does not include the fact that insect populations reduced by bats are less likely to evolve resistance to pesticides or to crops genetically modified to resist insects. Nor does it include bats’ benefits to forests.
It is in the farmbelts of the Midwest that the value of bats is highest, of course. Science provides a map of the United States illustrating bats’ estimated economic value, county by county. Utah is not heavily impacted. But our major food crops such as wheat and corn certainly are, and bats clearly help stabilize the supply and cost of our food.
Duane Jeffery is an emeritus professor of biology at Brigham Young University.
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