Backyard Naturalist: Bats: One of nature’s most beneficial animals

A few retail outlets that survived the onslaught of E-commerce greeted me this week with themed Halloween displays. Loath to be left out of the vanguard of those celebrating the so-called holiday, I decided to delight our readers with a closer look at Weston’s bats.

At the ancient Celtic festival of Samhain –celebrated on Oct. 31– folks warded off evil spirits by lighting bonfires. The fires attracted bugs which the bats recognized as an airborne banquet table. The Celts associated these shadowy specters with the spirit world.

That venerable spiritual connection is pretty much lost on us. We are less in awe of the only mammal who can fly than we are concerned that a bat will end up darting about the interior of our home and get tangled up in our hair or attach itself to the jugular vein, a la Dracula. Relax: our Weston bats are strictly insectivorous.

Bats have actually earned their rank as one of America’s most beneficial animals. Our nocturnal foragers contribute mightily to the control of garden and agricultural pests by consuming – in the case of breeding females – a nightly diet of bugs, whose combined weight matches that of the bat herself.

Our little flying mammals do not like the phrase “blind as a bat.“ In fact, Weston‘s big brown bat (measuring all of four to five inches and weighing a mere ½ to 3/4 of an ounce) has excellent eyesight. However, while hunting it relies instead on a superpower trait that even Batman would envy: echolocation. Our hero pulses out sounds above the human hearing range 20 times a second, listening for the bounce-back to pinpoint the location of flying food. As a bat nears its target, it will emit those beeps faster and faster until it’s honed in on the winged morsel. Bats retrace flight routes over and over, zipping along at up to 40 miles an hour. Those mosquitoes and beetles hardly have a fighting chance.

Like many animals with long lifespans, big brown bats (living up to 20 years in the wild) produce litters of only one or two pups. The adult pair mates in autumn. They then retreat to their hibernaculum to, well, hibernate all winter. During this time of torpor, heartbeats slow from 200 to 300 beats per minute to a mere 10 bpm. Delayed fertilization occurs in spring after bat metabolic processes have returned to normal. By June a new bat life has begun.

During the first few days of a pup’s life, it will attach itself to the mom‘s nipple and tag along for the ride during her nocturnal hunting rounds. Within a month, that pup will be spreading its own wings and catching its own bugs.

But there is a darker side to the bat story. Some small fraction of its population carries zoonotic diseases. (Yes, rabies). Bats can also sneak through cracks as small as a half inch and scare us out of our wits. So much for our troubles.

The bats themselves face existential risks: they are threatened by the scourge of white-nosed syndrome that spreads in the damp winter caves. The syndrome has caused a 99% crash in the populations of the little brown bat species. Big brown bats face the usual predators – cats, raccoons, and snakes who take some bats every season–as does the redoubtable great horned owl.

We can keep these flying pest-control wonders working for us by installing bat houses in the woods, minimizing pesticide use, leaving a few dead trees out back, and maintaining the mature forest portion of our lots. A dozen of our neighborhood critters rewarded my efforts with an evening flight display recently, lasting from dusk until deep dark, as they vacuumed up garden pests and bloodsucking mosquitoes.

“… In the evening,

The bats weave soft, black circles and their wings

Splash delicate ink upon the pale blue air…“

Joseph Auslander, Letter to Sappho, 1920s