(Subtitle: The Relationship between Bats and the Cost of Our Food!)
It is interesting how seemingly unrelated events come together for a totally unexpected outcome.
Event 1 – Early this summer, I was disappointed to see only two or three bats swooping and hunting over the yard and the adjacent pasture. Only several years ago there would have been dozens of bats filling the sky over that pasture. “Why the difference this year?” I wondered.
Event 2 – While in Lebanon State park last month (See) I encountered a cave. Posted on the path to the cave was a sign: “Cave Closed to the Public” with an accompanying sign explaining that the cave was closed due to the White-nose Syndrome (WNS) that is killing so many bats. I walked down to the cave only to see a group of young people going into the cave.
Later that week, while researching WNS, I discovered the Organization for Bat Conservation (OBC) in Bloomfield Hills, Michigan, not far from Dearborn, Michigan.
Event 3 – Coincidentally, my friend John and I were planning a trip to Dearborn, Michigan to visit The Ford Museum. Both John and I have become very interested in bat conservation, so I contacted the OBC, and through Danielle Todd, OBC’s Communications Manager, set a date and time to visit.
My goal was to learn more about the White-nose Syndrome, and how and why it was affecting bats here in Tennessee.
The OBC and the Bat Zone
The Bat Zone is the headquarters of the Organization for Bat Conservation, a nonprofit environmental education organization and wildlife sanctuary specializing in bats and other nocturnal animals. Each year, the OBC delivers classes to more than 250,000 people about the importance of bats, and creates positive environmental education experiences that lead to increased stewardship of our natural resources. The Bat Zone is located on the campus of the Cranbrook Institute, adjacent to the Cranbrook Institute of Science Natural History Museum.
Danielle met us in the lobby of the museum and guided us the Bat Zone. Along the way we passed a pickup truck filled with crates of ripe bananas; “Food for the fruit eating bats,” she said, anticipating my question.
Immediately upon entering their relatively small facility, we encountered several glass enclosures that, at first, appeared empty. Danielle pointed out several dark objects suspended from the wire ceiling of the enclosure, bats—specifically vampire bats.
Danielle explained that all of the bats and other animals in the Bat Zone were animals that would not survive in the wild due to injuries or age. They care for the animals and take them to classroom demonstrations in schools and other public information programs—including television programs.
Bats living in the Bat Zone include fruit bats, flying foxes, vampire bats, and many bats native to North America. Their enclosures are large enough for the bats to fly around in, roost, and feed. In addition to bats, they currently have skunks, reptiles, and a screech owl—all creatures of the night.
My focus was on a Tennessee native, the little brown bat. This bat, which is unable to fly and requires special handling, has its own private quarters in the facility. Amanda, an animal care specialist, brought the little brown bat out for photos.
The conversation shifted to WNS and why populations of bats were declining so rapidly.
WNS is a fungus, originally native to Europe, that has invaded North America. While many European species of bats seem immune to the effects of the fungus, many North American bats species are highly susceptible to it.
The key—and the key threat—is the bat’s energy management during hibernation. When temperatures are low and food is scarce, bats conserve energy by slowing their bodily functions. Bats have adapted the ability to effectively stop producing body heat and thereby slow their metabolism, heart rate and breathing rate to extremely low levels. For example, at rest the heart rate of a bat is about 300-400 beats per minute (bpm). When in torpor, i.e., hibernating, a bat’s heart rate can drop as low at 10 bpm.
The name of the disease refers to the white fungal growth—an irritant—found on the noses of infected bats, although it is also found on their wings. It is especially dangerous to bats that hibernate in large colonies in caves and mines. During hibernation, the bats sleep for long periods—several weeks or more at a time. Research has shown that WNS infected bats are awaking from their winter torpor as often as every 3-4 days as opposed to the normal every 10-20 days, resulting in a higher rate of arousal and use of essential body fat. Affected bats wake up dehydrated and hungry during the cold winters when there are no insects to eat. Additionally, hibernating in densely packed colonies quickly spreads WNS, having a devastating effect on the colony, and about 90% of the bats affected perish due to starvation. Bats produce only one pup per year, so the recovery rate of a colony’s surviving population is very slow.
Since the winter of 2006, White-nose Syndrome has killed more than 5.7 million bats in Eastern North America. WNS is a non-native, cold-loving fungus that is be found in the caves of the affected regions. It was first discovered in New York caves during the winter of 2006-2007, initially killing half of the wintering bat population. It is not clear how WNS traveled from Europe to North America. One plausible theory is that WNS mold spores were transported on climbing and caving gear brought to the United States by people who had explored caves in Europe.
It is not not clear exactly how the mold is transmitted between colonies, or spread throughout the region. Mold spores do fall onto the floors of caves, and it is possible that human traffic could transfer the mold from one cave to another. However it is transmitted, bats, especially the little brown bat, are dying off at the rate of a million individuals per year—far greater than their rate of reproduction.
A Department of Environmental Conservation survey shows a 93% decline of little brown bats in 23 caves at the epicenter of WNS. Currently, seven hibernating bat species are affected by the fungus: little brown bats, northern long-eared bats, big brown bats, tri-colored bats, eastern small-footed bats, the endangered grey bats, and the endangered Indiana bats. The disease is spreading rapidly and has the potential to infect at least half of the bat species found in North America, possibly completely eliminating several species.
The fungus persists in cave sediment after bat colonies leave their hibernacula (caves or mines) in the spring, lying in wait to infect next winter’s arrivals. Human activity such as frequent and random cave exploration could easily spread mold spores from cave to cave. Caves infected with WNS are displaying 90-100% bat mortality—wiping out most of the cave bat populations.
The bat conservation community is deeply concerned and involved with fighting the spread of WNS. Researchers are working to find a way to mitigate this fatal disease. Federal, state and local organizations are focusing on conservation of healthy habitats, containment and education.
Impact on Environmental (and Human Populations)
Dramatic reductions in populations of bats have occurred in recent years in the United States and worldwide. Bats have few significant predators. Only human activity is having a significant impact on the populations of bats. Adverse human activity includes destruction of habitat; direct killing, vandalism, disturbance of maternity and hibernating colonies; and use of pesticides (on their food insects) and other chemical toxins.
All bats in the eastern United States feed almost exclusively on insects and are therefore extremely beneficial. For example, bats are the only major predators of night-flying insects. Bats also face the problem of a very energy-expensive form of locomotion—flight. Therefore, a bat may eat more than 50% of its own body weight in insects each night amounting to 3,000 or more insects consumed per bat per night.
An individual bat can eat a thousand mosquito-sized insects every hour they are feeding, and they usually feed about 3-6 hours every night. By controlling insect populations, bats are critical to forestry, human health (for example, reducing West Nile disease—a mosquito-transmitted disease), and they save the agricultural industry billions of dollars each year. Without bats the agricultural industry will be forced to use more pesticides and thus food costs will also increase, not to mention the possible increased exposure of the human population to pesticides.
With no known way to eradicate WNS nor to increase the resistance of the bat population to this deadly disease, the only immediate control measures are protecting bat habitats, especially their hibernating caves and old mine shafts and make everyone aware of the real value of bats to the human community. This is not about conserving bats just for the sake of the bats, but for the economic value they provide through insect control and the protection of major food sources.
For more information, go to:
The Organization for Bat Conservation:
Bat Conservation International: http://www.batcon.org/
Bat Conservation in Tennessee, TNWBG: http://www.tnbwg.org/TNBWG_about.html
The day after leaving Wright Patterson AFB, we traveled to Bloomfield Hill, Michigan to visit and tour the Bat Zone at the Organization for Bat Conversation. Bats – The Basics explains how we came face-to-face with several species of bats, including the infamous vampire bat, but also we learned much about the devastating White-nose Syndrome that is destroying whole colonies of beneficial insect eating bats of North America.
Bats – The Basics continues the narrative of our trip to Michigan. This article describes how we came face-to-face with several species of bats at the Organization for Bat Conservation, including the infamous vampire bat and the endangered little brown bat.