The Carlisle Mosquito Online

Friday, September 11, 2009


Disease strikes bats, the offensive line against mosquitoes

We here in Carlisle take an odd sort of ironic pride in our insects, naming even our local paper after our most prevalent of pests, the mosquito. Although these biting bugs are certainly not scarce during any summer, this year has been particularly bad due to a combination of rainy conditions and a lack of bats. Yes, those little balls of brown fur that startle you accidentally when flapping around your attic are one of our main defenses against itchy red bumps.

The little brown bat (Myotis lucifugus) and big brown bat (Eptesicus fuscus) are the Bay State’s two most common species. The former prefer more rural areas and are most likely to roost temporarily in barns; the latter are more of an urbanite that finds its way into houses and garages.

According to the Massachusetts Audubon Society, our local bats can individually eat 600 insects an hour, and experts estimate that the bat population living within the Route 128 loop consumes 13 to 15 tons of bugs every summer.

Although bats can be infected with rabies, the disease kills them quickly and as a result, only about 1% of the bat population carries it. (Nonetheless, it’s best to proof the house to prevent bats from entering and use caution if they do gain access. See article page 12)

White Nose Syndrome

This year, though, our bats have fallen prey to a pernicious disease that has decimated their population. White Nose Syndrome or WNS was first documented in early 2006 and since then has wiped out entire bat colonies from the Canadian border of New York State to the southern parts of Virginia. Although the full workings of WNS are not currently known, it appears to strike during the bats’ hibernation period and causes low body fat, daytime flying and movement to cold or unprotected parts of their caves.

Research done by the US Geological Survey suggests that WNS is caused by a fungus that thrives in cold weather, hence its flourishing during winter and early spring. This is also the reason many caves have been closed to human access in New England. It is believed that explorers accidentally tracked the fungus from one cave to another, infecting new colonies at an alarming rate.

With so many bat colonies affected, state wildlife agencies are asking residents to help protect the remaining colonies by reporting sightings of bats with white fuzz on their faces or bodies, and any roosting groups of ten or more. Reports can be called in to 1-508-389-6300 or emailed to More information about Massachusetts bats and WNS can be found on the Mass Wildlife website.

Provide a home for bats

If you would like to help the bat population bounce back and have fewer mosquitoes on your property, giving bats a place to live nearby is a safe and natural way to do so. Providing such shelter also has the added bonus of making it less likely bats will attempt to take up residence in your attic, barn or garage by giving them a much better place to roost instead.

You can buy a bat box at many home improvement stores, or simply follow the instructions provided by the Massachusetts Fish and Wildlife department found at Either way, location is the real key to attracting bats to live there. Attach the box to the trunk of a tall, sturdy tree, pole or building at least ten feet off the ground and somewhere the bat guano will not bother anyone.

If you have a pond, river, or wetland on your property, try to place the box near it; this ensures that mosquitoes and other insects you’d like the bats to eat will be easy pickings. The box should face southeast or southwest and get as much direct sunlight as possible, as bats prefer to rest in a place that will stay warm at night, especially if they have young. Since each female bat typically only produces one offspring per season, it is particularly important to ensure that they have good breeding and whelping locations.

Mosquitoes will always be a staple of Carlisle, and hopefully bats will be too. As you sit on your deck in the evening or call your kids in from the yard as the sun goes down, glance up at the sky. If you’re lucky, you’ll catch the small, nimble outline of a bat or two already on the prowl for biting pests. Thanks to them, there’s a chance you can skip the bug spray in the morning. ∆

© 2009 The Carlisle Mosquito