Brian Heeringa is a wildlife biologist for the Washburn Ranger District of the Chequamegon-Nicolet National Forest and also a board member of the Midwest Bat Working Group. He recently shared his passion for bats as a Science on Tap presenter, offering information regarding bat populations in Wisconsin and across the country.
There are over 1,300 bat species in the world, accounting for one-fifth of all mammal diversity on the planet, Heeringa said. For that reason, bats are very important, not only to the environment, but to the economy and even human health. Bats, he said, have been around for 50 million years, and have not changed much in that time.
All bat species in Wisconsin, and 70 percent of bats species worldwide, eat insects. There are eight species of bats in Wisconsin, including the little brown bat, big brown bat, Northern long-ear bat, Easter red, Hoary and silver-haired bat, which are all found in the Northwoods. The tri-colored bat, Heeringa said, is found primarily in the southern part of the state. While some other species eat fruit, frogs and fish, their impact on farming and savings in pesticide and insecticide use likely impact the economy the most.
Bats need to eat one-half to one times their own body weight every day. One study in Wisconsin found a little brown bat could eat up to 1,000 insects in just one hour. This is especially important in a farming state such as Wisconsin, Heeringa said. In Wisconsin alone, it is estimated insect-eating bats account for $700 million to $1.5 billion in savings to farmers from pesticides and insecticides they would otherwise have to apply to their crops to keep away the same amount of pests.
Bats do have natural predators, including owls, hawks, raccoons and cats, but there are other threats as well. Human interaction and habitat loss play a large role in bat populations. Pesticides and insecticides used can change the insect availability, leading to less food for bats. Climate change, too, could potentially affect bats as environments shift, with implications for plant species and the related insects found with and on those plants. Even wind energy, an important renewable energy source for humans, can cause mortality in not only birds but bats as well. Possibly one of the biggest threats to bat populations, however, is a fungus knows as White Nose Syndrome.
Many have heard of White Nose Syndrome, or WNS, which has decimated some bat populations, with up to 80-90 percent of some populations succumbing to the disease within three years of infection. The disease, first found in 2006 in the United States, was found in Wisconsin in 2014. It is a fungus affecting the damp, cool caves and other areas where most bats hibernate. More than half of all bats hibernate as a way to survive through the winter. Those that migrate, the tree species of bats, are not as likely to be affected by WNS. Caves and other underground compounds are environmental reservoirs for the soil-loving fungus, giving it the perfect conditions.
The disease is now in 33 states and seven Canadian provinces and moved west from the East Coast, and was most recently found in Washington state. Heeringa said one of the most precipitous declines in wildlife species has been observed with WNS. It can easily be moved from one location to another by humans. Those exploring caves and other hibernacula can pick up the fungus on their boots, clothes and gear. When that adventurer then enters another cave or area where bats hibernate, the fungus can be transported quickly to that new location.
'We are being very proactive'
There is a good deal of research going on regarding WNS, Heeringa said, because bats are so important to the economy from a farming and food perspective. Some vaccines are in development, but the biggest challenge is how to disperse those vaccines with populations that may number in the millions in some areas and, in other areas, be so spread out it proves difficult at best to find the bats, let alone inoculate them.
"Wisconsin is kind of leading the charge," he said. "We are being very proactive and we have many field trials going on right now."
One of those field trials looks at how the environment can be treated to, for instance, rid a cave of the fungus without otherwise upsetting the delicate ecological balance of the other organisms there. It has been determined that once the fungus is found in a hibernation site, even after the bats are gone, if more bats move into that site, they are still susceptible to the fungus.
Another study uses fluorescent powders and UV lights to get a better idea of how the powdery fungus can be transferred from an infected bat to its environment. The powders are put on bats, who are then allowed to just do what bats do, entering their hibernation sites and moving around those sites. Once the bats are out of hibernation, researchers can move in with UV lights to see where each of the colors has been spread. This should help give an idea of how the fungus causing WNS is moved.
WNS creates a white powdery substance, usually on the snout and other soft tissues of bats. This is where the disease gets its name, but Heeringa said there are other signs bats may be affected. The powdery fungus irritates the skin of the bats, waking them up. They start to burn through their stored resources by being awake much more frequently than their hibernation cycle would normally allow. They go out in search of food and water and usually die of dehydration as they deplete those resources. For that reason winter surveillance is important, as that can often point to WNS-infected bats that may not otherwise be found.
But it is not all "doom and gloom," Heeringa said. There are things people can do to help the plight of bats in Wisconsin. There are many citizen science programs that surround bat populations. Spring and summer monitoring are getting underway now, with volunteers heading out on water and land routes with special equipment used to detect bats and even discern which species are present.
Bats use echolocation to find food and to keep from crashing into objects as they dart through the air. This echolocation can keep a bat from running into something as small as a human hair while navigating. They can emit over 500 pulses per second from their mouth or nose, allowing them to "see" where they are going. Because the noise is so loud to the bat itself, Heeringa said, they have a mechanism allowing the bat to close off their ears while emitting these sounds. However, the sounds are ultrasonic, so humans cannot hear them. Special equipment is used during bat monitoring surveys to capture these sounds, which can then be translated through a computer program.
From these translations, researchers and volunteers can calculate population estimates and also learn which bats are present in which locations. Bat monitoring goes on throughout the Northwoods, and with some interesting observations in the past. When monitoring a lakeshore, for instance, volunteers and researchers have found that even a small amount of natural shoreline can hold far more bat activity than a developed stretch of shoreline.
Heeringa said individuals can help bat populations by doing small things such as erecting a bat house or creating a bat garden. Bat gardens are similar to native planting gardens, but with the addition of a bat house. He said gardeners can also add plants that bloom at night, attracting insects which are an inportant food source for bats. He also recommended reducing non-native invasive species, which may be reducing the bats' food source. Whether an individual undertakes a volunteer role, signs up for a spring and summer surveillance route, or simply makes minor modifications to their own property, those interested in helping bats have several options.
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