04/29/2016 Bat on the Deck

Bat

This poor creature was found on my deck. In order to identify it, I used a taxonomic key. The key required that I make measurements, such as the length of the forearm. I was brave (or foolish) to pick up the bat but I did wear gloves. The bat turned out to be an Evening Bat, a common insectivorous species. Robert Benson photo.

29 Apr 2016 – There’s Some “THING”…on the Deck!

I like to start my morning on my deck.  I drink my coffee, commune with my cats (my husband says I am counting them), and see what birds are coming to the feeders.  It is a very pleasant time of day.

However, on one morning recently, I was making my coffee and happened to glance out the French doors.  The usual cats were there waiting and the dog was lounging near the railing.  But something else caught my eye.  It was almost round, black and had a fuzzy, silvery center.  I thought it might be a small, dried out sunflower head, a “toy” that the cats had brought to the deck to play with.

Or it might be one of their trophies.  Surely it wasn’t an animal, was it?  I leaned down to get a closer look and …oh no!

            There was some “thing”… on the deck!  The “thing” had a tiny dog-like face and big ears.   Its black wings were folded around its silvery, dew-covered chest.  It was a bat!

            I eyed it from a distance as I drank my coffee.  I read the bat sections in my mammal field guides.  As I looked through the bats pictured in the field guides, I couldn’t tell what type of bat this curled-up, dead thing was.  I was going to have to “key it out.”

What does “keying it out” mean?  Following a taxonomic key is exactly like playing the old game of 20 Questions.  The key begins by offering two choices (like yes or no) to a question.  Depending on which you choose, you are led to the next question…and a choice, and so on, until you reach a final question that identifies the species.  A shortened version might go like this:  Is it an animal?  YES.  Is it a mammal?  YES.  Does it have wings?  YES.  Are its forearms less than 40 millimeters long?    What?

Obviously I needed to make some measurements on the body.  In other words, I needed to pick up the bat!

Okay, okay…I know.  Don’t touch a dead bat!  Even the mammal guide warned “DO NOT PICK UP AND HANDLE BATS.  They can carry rabies, and a bat allowing itself to be handled may be sick.  If you are bitten by any mammal, seek medical attention.”

I was too curious to be sensible.  But I did put on a pair of surgical gloves.  When lifted to the railing, the bat slowly opened its mouth.  So slowly…I thought I had imagined it.  But the evidence was there:  a mouth full of tiny, sharp teeth.  Then it slowly closed its mouth and its chest rose as it took a deep breath.  I hoped it wasn’t screaming or sighing ultrasonically.  It didn’t appear to breathe again.

Bat house

Bats are enormously important to the well-being of our planet. The more than 900 species worldwide pollinate plants, eat crop pests, and carry seeds to new locations. Evening Bats especially benefit from us humans erecting artificial roosts for them. This “bat house” is a good example of a roost you can erect to bring bats to your yard. Audubon Society photo.

So, I spread its wings and measured the length of the forearm.  Then I uncurled the tail and saw that the tail was connected to the legs by a membrane, the interfemoral membrane.  Only the last few millimeters of the tail were free.  I measured the ear length; the ears were less than an inch long (<25 mm) and in front of each ear was a funny structure, a projecting flap of skin called the “tragus.”  The tragus was pointed and curved slightly outward.

The Key to Chiroptera (bats) had led me to two possibilities:  the Big Brown Bat, and the Evening Bat.  The way to tell the difference between the two was by the teeth.  Uh-oh.  I had to open its mouth.  What if it was still alive and bit me?  What if it was dying of rabies?  Like you, I’d heard of those terrible rabies shots.  Again, the mammal guide comforted me with the statement that “the modern rabies vaccine is now a series of small injections in the arm, replacing the painful old stomach shots.”   I could deal with that.

So with my husband’s help, we pried the bat’s mouth open with two matchsticks.  We looked at the incisors.  Did it have one pair or two pairs of incisors?  My bat had only one incisor on each side of its jaw.  A single pair of upper incisors meant that the bat was an Evening Bat (Nycticeius humeralis); we had keyed it out.

We also discovered that it had a swelling on the right side of its body, possibly a tumor or an infected injury.  It seemed unlikely that it had rabies.  But my husband, ever cautious, had me carry it with gloved hands to the burn barrel.

Evening Bats are common in the Eastern half of the United States.  Like nearly all bats, the Evening Bat is a beneficial species.  Merlin Tuttle in his The Secret Lives of Bats (2015) points out that bats are vital to the balance of nature: they pollinate many plants, disperse seeds, and especially, eat tons of insects.  Each night a single bat eats up to 1000 insects.  According to the Texas Parks and Wildlife Department (TPWD), a colony of 300 of Evening Bats was estimated “to consume 6.3 million insects per summer, dining mainly on spotted cucumber beetles.”

These bats prefer to forage for flying insects at the edges of mature forests, in clearings and along waterways, primarily in the early part of the night.  By day, this species roosts in hollow trees, behind loose bark, and in buildings (but not in caves.)   TPWD states that “Loss of old-growth timber has deprived this species of its original roosts” and has driven them to seek shelter in old buildings.  However, many wooden barns and other old buildings are being replaced by structures that bats cannot use.  So the Evening Bat is declining in numbers.  TPWD suggests that these bats would benefit greatly from artificial roosts (bat houses.)

That’s why I have a bat house.  They are readily available in several sizes (holding from 20 up to 300 bats) and are inexpensive.  The houses are also fairly simple to construct from plans.  Both plans and dozens of different houses are offered on Amazon.com    Dare I request another one as a Mother’s Day present?  Why not?

The bats would benefit and so would we.  Evening Bats are big consumers of insect pests and they coexist well with humans.  I would like their help in keeping my garden pest-free.  And just to be sure I am also going to get a supply of ladybugs at the upcoming Beeville Garden Club Plant Sale (on Saturday, April 30th.)   The ladybugs will eat insects by day and the bats will feast on night-flying pests!

If you would like to offer comments, please click through to the discussion page