SHERIDAN – With Halloween around the corner, plastic and Mylar bats are out in full force for a few more days in schools, homes and stores. However, thousands of real bats have been flying above us all summer and in fact, have filled Wyoming skies for millions of years.
Bats are astonishingly diverse and make up more than one-fifth of the mammal species known to exist. There are more than 1,200 species of bats worldwide, with 47 species found in the United States.
“Since there are so many species, bats are super diverse,” said Leah Yandow, a Nongame Biologist for the Wyoming Game and Fish Department who works with bats. “Some are carnivores, some eat fruit, insects, fish, nectar and only three species drink blood. In Wyoming, they are all insectivorous.” Bats serve several important functions, including control of insects, plant pollination and plant seed and nutrient dispersal across the landscape through their droppings. In Wyoming, bats make outdoor living for us a lot more enjoyable by engaging in aerial warfare on many pesky insects such as beetles, moths and mosquitoes. They are so efficient at their work that one of Wyoming’s most common bats, the little brown bat, can eat more than 1,000 mosquito-sized insects in one hour. It is sobering to think of how many tens of thousands of insects that hundreds of bats consume each night in our area and how unpleasant, and indeed itchy, life would be without them.
“A study was done that showed $3.7 billion is saved annually by bats eating agricultural pests in the continental United States,” said Yandow. “And so in Wyoming they likely make a huge difference on eating herbivorous insects.”
Worldwide, bats pollinate hundreds of plant species including bananas, peaches, mangoes, avocadoes and cashews, as well as agave and sugar cane plants from which tequila and rum is produced.
“Bats have some interesting life history traits,” said Yandow. “Most species often live to be 20 to 30 years old in the wild, which is very long time for such a small mammal. And, most bat species in Wyoming only produce one young per year, which makes them more vulnerable to disturbance because they are particularly slow to recover for mammals of that size. For example, many mouse species reproduce several times per year with large litters, which is more typical for mammals of bat size.”
Twelve species of bats are found regularly in Wyoming and are considered residents. Another six species are occasional visitors to our state, though unlike other tourists, they are not here to see Old Faithful, but to eat our bugs.
Obviously, getting population and diversity data on animals that come out only at night and are scattered across the landscape, many feet above ground, is a challenge. However, to get an idea of how many and what types of bats are found in a particular area, biologists use two methods. One tactic is to set up mist nets across bodies of water or in other suitable bat habitat. As the bats forage, they become entangled in the fine threads of the net. Biologists can then don gloves, gently untangle the furry creatures, identify the species and take measurements such as length and weight. Another method is more hands-off and takes advantage of one the most well-known traits of bats, echolocation. By using high-frequency clicks or calls emitted from their vocal chords and then listening to the ‘echoes’ that bounce off objects and back to them, bats can navigate through dense vegetation, avoid moving objects and locate flying prey. The system is so highly developed in some bats that they can detect an object as thin as a human hair in total darkness.
Echolocation clicks are unique to each species, allowing biologists to record the sounds and later determine who made them.
“We set out acoustic monitors in areas where we expect to have high concentrations of bats,” said Yandow. “Those monitors will capture any echolocation noises from bats that are flying by. They will record those and we download those data and we can tell which species came by on that particular night in that particular area.”
“The program we use is pretty amazing,” she continued. “It looks at the inflection point and the slope, how quickly the pitch changes, how long the call is, do they use narrow or wide range, so there is a whole bunch of different characteristics about a call that make it unique to a species.”
Bats are not newcomers to Wyoming. In fact, the oldest discovered bat fossil was found in Wyoming in 2003 and is estimated to be 52 million years old. The nearly perfect fossil settled a long debate among bat scientists…what developed first in bats, flight or echolocation? The fossil showed that in fact, flight developed first and echolocation developed later.
However, echolocation is not used by all bats. Bats that eat fruit, nectar, fish or amphibians do not rely strongly on echolocation and instead, have well developed senses of sight and smell, debunking the myth that bats are blind. There are in fact, no species of bats that are blind.
More than half of U.S. bat species are currently listed as endangered or are in severe decline. Their slow reproduction rate makes it difficult for bat populations to recover from disease or other mortality factors. A current serious threat to bats is white-nose syndrome. It is caused by a fungus that grows on bats as they hibernate, causing them to emerge from hibernation early to forage, even though there are few insects available for food. It was found in a New York cave in 2006 and since then it has spread west and south to 23 other states and caused the death of millions of bats, with 100 percent mortality for some colonies. The fungus has not been documented as far west as Wyoming yet, but it was discovered in two Minnesota caves in August.
Photos and information about bats, including how to safely remove them from your property, or attract them with bat houses, can be found on the website of Bat Conservation International at www.batcon.org