Exploring The Last Green Valley – Monitoring Bats in The Last Green Valley
Monitoring Bats in The Last Green Valley
I first met Kate Moran of the Connecticut Department of Energy and Environmental Protection a few summers ago. I knew Kate from phone conversations and e-mail correspondence when she was coordinating the Connecticut Midwinter Eagle Survey so I was pleased when she stopped by our office in Danielson to introduce herself.
I soon discovered that she didn’t want to talk about eagles when she asked me if I liked bats. I do like bats, especially when I see them flying around our yard eating mosquitoes. Viewing bats in their natural habitat is much preferred to finding one inside my house!
Kate told me about white-nose syndrome and how it was killing vast numbers of bats. She asked if I wanted to help monitor bats as a way to determine the exact impact of the disease. I jumped at the chance.
Information about the disease can be found on a US Fish & Wildlife Service fact sheet www.whitenosesyndrome.org and here is a quick review:
- White-nose syndrome (WNS) is a disease affecting hibernating bats. Named for a white fungus that appears on the muzzle and other parts of bats, it is associated with extensive mortality of these animals in eastern and mid-western North America. First documented in New York in the winter of 2006-2007, it has spread rapidly across eastern and mid-western United States and eastern Canada.
Bats with WNS act strangely during cold winter months, including flying outside during the day and clustering near the entrances of caves and other hibernation areas. Bats have been found sick and dying in unprecedented numbers in and around caves and mines. WNS is estimated to have killed more than 6 million bats in the Northeast and Canada. In some sites, 90 to 100 percent of bats have died.
- Many non-governmental organizations, universities and state and federal agencies are investigating the cause of the bat deaths. A newly discovered fungus, Pseudogymnoascus destructans, has been demonstrated to cause WNS. Scientists are investigating the dynamics of fungal infection and transmission and are developing ways to control it.
- More than half of the 47 bat species living in the United States hibernate to survive the winter. Seven cave-hibernating bats, including 2 endangered and 1 threatened federally-listed species, have been confirmed with WNS. The fungus has been detected on an additional 5 species, including one endangered species, with no confirmation of disease.
- White-nose syndrome has continued to spread rapidly. As of May 2016, bats with WNS were confirmed in 29 states (including all 6 New England states).
- In 2011, the US Fish & Wildlife Service and a team of federal and state agencies and tribes prepared a national white-nose syndrome response plan to address the threat to hibernating bats. The plan is a framework for coordinating and managing the national investigation and response to WNS. The plan outlines actions necessary for state, federal and tribal coordination, and provides an overall strategy for investigating ways to manage WNS and conserve bats.
- Biologists in New York and Vermont have found up to 50 percent of marked little brown bats at a few test sites surviving from one winter to the next in recent years, giving some hope that this species might one day be able to recover. Little brown bat populations at these sites remain at less than 10 percent of their pre-WNS size, however.
- Scientists have developed new ways to detect Pseudogymnoascus destructans on bats and in the environment, including using UV light and molecular analyses.
- Researchers have made significant strides in understanding disease response of hibernating bats and factors that influence bat vulnerability to WNS.
- Studies of natural bacteria and skin microbioma of bats have led to new lines of research for treatments using biological or biologically-derived agents for bats at risk of WNS infection. Some of the potential treatments are moving to limited field testing.
Kate has been coordinating volunteers throughout the state to help monitor bat populations. Gathering the data over several years will help to determine the overall population numbers and determine the extent of the WNS impact.
Kate described for me the two ways they monitor bat populations and asked which one I was interested in doing. The first is by visiting documented bat colony locations and counting bats as they exit the location (typically an old barn or building) at dusk to hunt insects. The second way is by using a highly-sensitive recording microphone to detect and record the echolocation calls bats use to hunt. I elected to use the recording device and enlisted my wife Julianne to help.
Here is how the Bat Conservation Trust in Great Britain describes echolocation:
Bats are not blind; in fact they can see almost as well as humans. But to fly around at night and hunt for insects in the dark bats use a remarkable high frequency system called echolocation. Echolocation works in a similar way to sonar. Bats make calls as they fly and listen to the returning echoes to build up a sonic map of their surroundings. The bat can tell how far away something is by how long it takes the sounds to return to them.
These calls are usually pitched at a frequency too high for adult humans to hear naturally. Human hearing ranges from approximately 20Hz (cycles per second) to 15 to 20 kHz (1000Hz). In comparison, some bats can hear sounds up to 110 kHz in frequency. By emitting a series of often quite loud ultrasounds that either sweep from a high to low frequency bats can distinguish objects and their insect prey and therefore avoid the object or catch the insect.
Individual bat species echolocate within specific frequency ranges that suit their environment and prey types. This means that we can identify many bats simply by listening to their calls with bat detectors.
The microphone or “bat detector” that we used was about 12 inches long and fixed to the top of our car by a strong magnet. A cable attached to the microphone extended through the passenger side window to a laptop computer with sound recording and GPS mapping software.
We were asked to monitor a 20-mile stretch of mostly wooded habitat that followed small back roads from Windham to Putnam. We had to drive the route one evening a week (with no rain) during a specific window of time at dusk when bats typically feed. We maintained the exact route using the GPS Google Map software and maintained a relatively constant and slow speed of 20 miles an hour. It usually took us an hour to drive the route and we alternated starting points each week, beginning one week in Putnam and the next in Windham.
We were trained in how to use the equipment to record bat echolocation calls. The bat call recordings were synchronized with the Google Maps and GPS locations to provide an exact number of bats at an exact location along the route.
CT DEEP is interested in gathering as much data as possible for scientists to analyze. They frequently rely on volunteers to help gather data and we were more than happy to help. Julianne referred to our car as the bat mobile and joked about yet another exciting “date night” with Ranger Bill! We did our recording during the month of August, then afterwards the equipment was returned to the scientists at CT DEEP and the data downloaded for analysis.
I checked with Kate in preparation for this column. She wishes she had better news to report and told me, “Bats in Connecticut have not rebounded to any significant degree. They have a low reproductive rate with only 1 pup per year. With the kinds of declines caused by WNS (in some species 90%) it may take decades to recover.”
The work that Kate Moran and her colleagues at CT DEEP are undertaking is very important to understanding the many impacts on our region’s wildlife – the flora and fauna that make this region so special. We were happy to play a very small part in helping to gather data on the bat population in Connecticut. If you are interested in this program, contact me for more information.
We live in a special region that relies on both experts and volunteers to monitor, document, and pass on their knowledge about our natural resources. This knowledge helps us care for it so all can enjoy it.
Bill Reid is the Chief Ranger of The Last Green Valley National Heritage Corridor and has lived in the region for more than 30 years. He can be reached at firstname.lastname@example.org.
The Norwich Bulletin is granted first serial rights and associated electronic rights to publish the preceding article. The Last Green Valley, Inc. retains all other rights to the work.
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