week of  2/6/02
 
 
 


The Naturalist's Corner
By Don Hendershot
Humans are notorious for anthropomorphizing. That is attributing human characteristics to non-human creatures and objects. Bunnies are cute and cuddly; snakes are cold and slimy, therefore bunnies are good and snakes are bad. Biologists, however, are scientists so rather than “good” or “cuddly” and “bad” or “slimy” they couch their anthropomorphism’s in scientific terms like “beneficial” or “pest.”

In truth the natural world operates totally outside the anthropocentric ideals of good and evil. Crocodile or koala, animals simply live their lives to the best of their ability in the ecological niche they are adapted to. Their value or worth is intrinsic. Crocodiles are not bad because they eat koalas. It can’t be equated to Hannibal Lecter stalking his next victim.

I was reminded of nature’s oblivion to human labeling the other evening as I watched a bat circling in the full moon’s glow chasing insects lured out by the unseasonably warm winter evening. While bats were once cloaked in superstition and dread, they are generally thought of today as beneficial or good critters because of the huge numbers of insects they ingest. These nocturnal bug zappers share the night skies with another creature, generally thought of as “good” in anthropocentric terms; owls.

However, when these two good guys meet in the darkness it’s generally bad news for the bat. Owls are one of the few creatures that appear to regularly prey on bats. In some areas with a high density of owls, bats exhibit what biologists call lunarphobia. They greatly reduce their night time activities during bright nights associated with full moons to lessen the risk of becoming owl food.

Almost any species of owl, or any other predator that feeds on small mammals, will take a bat given the opportunity. Some species of owls seem to have a greater proclivity for bats than others. Bay owls and eastern screech owls have been observed staking out caves where bats roost and capturing them in flight as they exit.

In a recent post to Carolina Birds listserv, South Carolina state parks biologist Irvin Pitts noted the results of a survey he conducted in the fall and winter of 1986 - 1987. Pitts analyzed 27 barred owl pellets collected from a roost at Pleasant Ridge County Park in Greenville County, S.C. He found the remains of 61 different animals represented. Bats (almost exclusively eastern red bats) made up the largest segment of prey species with 16 individuals.

The fact the majority of bats recorded in Pitts’ survey were red bats is probably more attributable to supply and demand than any kind of bat-preference on the part of the barred owls in questions. Eastern red bats, Laisiurus borealis, would be the most common bat active, in that area, during that time of year.

Eastern red bats are year-round residents in the southern US but northern animals migrate in the fall from their nursery sites in the northern US and Canada to the southeastern US and northern Mexico where they hibernate. Eastern red bats are cold hardy and some overwinter as far north as Ohio. On warm winter evenings male red bats commonly roust from hibernation to feed.

While not equipped with echolocation like bats, owls are quite suited to their nocturnal niche. Their large eyes enable them to gather light giving them great night vision. Binocular vision (both eyes in the front of their head) allows them to see in three dimensions giving great depth perception.

The rounded disk-like face actually directs sound waves to the owls ears. Owls ears are asymmetrical, the right ear being slightly higher on the head than the left ear. This gives the owl three dimensional hearing as well as three dimensional sight.

Add these facets to the owl’s silent flight, created by serrations along the leading edge of the flight feathers, sharp, strong talons and hooked beak and you have a very efficient nocturnal predator. One that makes no moral or ethical distinction when faced with the prospect of dining on “good” bats.

(Don Hendershot can be reached at don@smokymountainnews.com)