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Small native species -- 'nature's bug zappers' -- great for mosquito control

Nothing spooky about peninsula bats

Posted: Friday, October 26, 2001

Bats, as they flit about in the gloom of darkening skies, are spooky to many people. But the little-known bats of the Kenai Peninsula are more treat than threat.

This area is home to the descriptively named little brown bat, the most widely distributed and abundant bat in North America. Its range extends to the East Coast and south into Mexico.

Scientists call it Myotis lucifugus, a name that means "mouse-eared critter that avoids light."

"I know they hang around," said Ted Bailey, retired research biologist from the Kenai National Wildlife Refuge. "There is a lot we really don't know about them."

The bats are fairly common, but difficult to see. They are small, fast, evasive and unlikely to be out during daylight.

"When I've seen them most is flying low over a lake on a calm evening," Bailey said.

The little brown bats of Alaska are unlikely to be out for Halloween. Most already have hunkered down for the winter. But this is a good time of year to consider where you do -- or do not -- want them roosting on your property.

The bats are not dangerous. Nationwide, only 15 human deaths in the past 40 years have been due to bat-transmitted rabies, and none of those were in Alaska, according to information compiled by the University of Michigan and the federal Centers for Disease Control. To be safe, never handle a bat that seems sick.

On the plus side, bats eat an enormous amount of flying insects. Although their favorites are moths, they chow down on mosquitoes as well. One bat can vacuum 500 insects per hour out of the air, so they have been called "nature's bug zappers."

If a bat flies around your head in the summer, it is most likely picking off the insects trying to bug you.

The world's only true flying mammals, bats are remarkably adapted for the hunt. They use echolocation, like radar, to orient themselves and track objects in the dark.

Bats can catch flying insects in their mouths, but they also nab them with their wing tips. They flip the prey into a pouch between their tails and back legs, then dip their heads to snap them up without breaking their flight.

During the warm seasons, they come out at dawn and dusk, foraging two or three hours at a time. They prefer to stay near water, where bugs abound.

In the fall, they mate and migrate to hibernation colonies. Exactly where Alaska's bats go remains a mystery. No one has studied them on the peninsula, but evidence elsewhere suggests they migrate toward coastal areas, hole up in nooks and crannies or sometimes move indoors with humans. In other parts of the continent, they migrate as far as 200 miles and congregate in caves and hollow trees.

Little brown bats are true hibernators, whose heartbeats slow and body temperatures drop to about 40 degrees. They do not eat all winter, but survive on stored fat.

In one experiment, a bat survived its body being chilled below freezing. They also thrive in high heat and are believed to have the widest range of body temperature of any vertebrate.

Although they breed in the fall before bedding down for the season, fertilization is delayed until spring.

Females are pregnant 50 to 60 days. They gather in nursery colonies in late spring or early summer, preferring warm places such as attics to raise their young, which are born blind and hairless. The mothers carry around baby bats at first, then leave to hang around, literally, in groups at the nursery site.

Young bats become independent when they are about a month old but are not completely mature until 1 or 2 years of age. They live a surprisingly long time for such small animals -- 20 or 30 years -- perhaps due to their ability to slow their metabolism during their frequent rests.

Bats have benefited from human settlement, finding attics and sheds a cozy substitute for caves and hollow trees.

But while bats in the yard are cheap mosquito repellent, bats in the family belfry can get messy.

They are so small -- with bodies about 2 inches long and weighing about as much as three pennies -- that they can squeeze into surprisingly tiny openings.

If you want to evict bats from your premises, it is best to wait until they move out for the season, then block all potential entry spots. Plug or caulk openings such as louvers, vents and chimneys, or cover them with fine-mesh hardware cloth.

If the bats are reluctant to move on, Integrated Pest Management of Alaska notes that they dislike the smell of mothballs.

The company warns homeowners to be careful that all bats are actually out before sealing entrances. If you trap bats inside, they may become frantic, thump around inside walls or end up in your living room at an awkward time.

IMP recommends cutting the bottom off a plastic bag and attaching it around the opening. That way exiting bats can wriggle out, but when they try to return the hanging plastic blocks their entry.

The best option may be to keep bats nearby in more appropriate accommodations.

You can build bat houses, analogous to bird houses, to encourage them to stay around your yard. Bat house plans and other information on being a good bat neighbor is available from naturalists and the advocacy group Bat Conservation International.

Then you can bet that next time you see bats flitting in the twilight near your home, it will be the mosquitoes, not you, that will be spooked.



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