The Pond

 

 AERIAL DANCERS

Dusk was falling, and it seemed that time was suspended. The concerns of the day were

past and the ones of tomorrow didn’t exist yet. Reveling in the moment, I settled in to

watch the evening’s performance of the aerial dancers. Looking up into the warm spring

sky, I watched the dancers twist and turn, changing directions in midair as they sped

forward and back, up and down. The bats were coming out to feed!

I have always been an advocate of bat conservation—not only are they fascinating

but as the earth warms, insects are becoming more and more plentiful. Bats feed on

hundreds of thousands of tons of insects yearly. If you don’t enjoy mosquitoes buzzing

around you—then employ the most environmentally safe and effective way to rid

yourself of them—bats! All four types of bats in central Virginia are insect eaters and can

consume 600 to 1,000 mosquitoes per hour.

Bats are integral to pest control and maintaining a healthy environment. You can ensure

they stay around to keep the mosquitoes in check by providing a bat house

where they will roost during the day. Depending upon the species, bats will either

hibernate or migrate south during the winter.

                                                                      Photo Credit: Hitchhike

Bat Conservation International ( www.batcon.org ) has instructions on how to build a bat

house and also offers them for sale. If you prefer to buy a bat house from a retail outlet,

check to make sure that it is a certified bat house—bats have specific needs for roosting.

Bat Conservation International enables one to peek into the world of bats by way of a

webcam mounted inside a bat roost. Go to the website and you can enter this exciting

world!

According to M. Brock Fenton, professor of Biology and Bat Echolocation; bats produce

a variety of vocalizations: squeaks and squawks that they make to other members of the

colony while roosting; calls that mothers and young make to each other, and sounds that

bats produce to defend their feeding territory.

Last but not least, is a high-frequency vocalization known as echolocation. These

sounds are inaudible to us. Yet echolocation allows bats to “see” with

their ears.

This discovery was made in the 1700’s by Lazarro Spallanzani, an Italian scientist. It

was not until the 1930’s that it was proven by Harvard researcher Donald Griffin when he

coined the term echolocation to describe how bats emit high-frequency calls through their

nostrils or voice-box that bounce off objects and return to them, informing them where the

object is located. This explains how bats are able to catch insects in midair and turn on

much less than a dime! This is also why bats cannot get caught in a person’s hair. Their

navigational abilities are far too exact to make such an error.

Little Brown Myotis

However, bat vocalizations can be heard with the aid of bat detectors. These are

microphones that are sensitive to high-pitched sounds. Bat detectors are used to

identify bats by the sounds they emit, much like birdwatchers identify birds by their

songs. The rate of a bat’s call changes as it gets closer and closer to its target—perhaps a

June Beetle or a moth. If you watch a bat under a streetlight with the aid of a bat detector,

you will notice that the calls begin at a higher frequency and sweep down to a lower one.

As the bat gets closer to its target, the calls become shorter and shorter. This entire

process takes less than half a second.

Bats belong to the order Chiroptera, which is subdivided into two suborders:

Microchiroptera and Megachiroptera. The bats in central Virginia are

Microchiropterans—which are small insect-eating bats. The Big Brown Bat (Eptisicus

fuscus), the Little Brown Myotis (Myotis lucifugus), the Eastern Red Bat (Lasiurus

borealis), and the Eastern Pipstrelle (Pipistrellus subflavus) are the four species native to

this area. They can be observed both in rural and suburban areas. Look for them in fields

and wooded areas—often around bodies of water where insects congregate, or while

taking a walk at dusk.

All four species are active during the spring, summer, and some until the early fall. All

hibernate during the winter, except the Eastern Red bat. Interestingly, only some of the

Eastern Pipistrelles hibernate—others of the same species will migrate during the winter.

Young are born during June or July. Bats give birth to delicate, helpless babies who

depend upon their mother for all their needs. Unfortunately, bats produce on average

only 1-2 young per season, which places them in a precarious position as development

destroys many of the caves, tree hollows, rocky outcroppings, and old buildings where

they would normally roost and raise their young. This is another reason why bat houses

are so vital to the welfare of these delicate animals.

Eastern Pipstrelle

Jill A. Deming, MA