Mrs. O'Donnell's Lecture Notes

Bats

Vampire Bat

Chiroptera Desmodontidae

Photo Source Birmingham Zoo, Huntsville, Alabama

Bats are from the Order Chiroptera which literally means "flying hand".  We learned about two taxa of bats:  Microchiroptera (microbats) and Megachiroptera (megabats).  Microchiroptera bats primarily use echolocation to hunt for food.  Megachiroptera use their eyes to search for food.  Microchiroptera are carnivores and Megachiroptera are vegetarians.  

Bat Mechanics

Bats are the only flying mammal in the world.  Bats are covered with hair and nurse their young just like every other mammal.  A bats' wings are actually hands and fingers.  They have fingers with joints, elbows, and shoulders.  Between their fingers, lies a thin membrane that is full of blood vessels.  If they accidentally tear one of their wings, the blood vessels help to repair the damage so that they can fly again.  When bats fly, they use their pectoral muscles to power their wings.  They use the same muscles we would use when we are swimming a breast stroke or butterfly stroke.

When bats are flying it's difficult for humans to track their movement because they move so quickly.  A bat can change its flight path by altering the shape of their wing.  There are millions of ways that a bat can change its wing shape allowing it to move more quickly and faster than any other flying object.  A bird doesn't have that ability.

When bats roost they hang upside down.  It's speculated that bats can sleep upside down because their heart rate is so low, thus decreasing blood flow to the brain.  Hanging upside down allows a bat to fly away quickly.  They can't take off from an upright position because of the way their legs, hips, and spine are designed.  Vampire bats are the only bats that you'll see crawling around on the ground when they hunt their prey.  When a vampire bat wants to take off, it has to climb up to a position to where it can take off.  

At rest, a bats heart rate is around 20 beats per minute, whereas our heart rate at rest is around 70 beats per minute.  When we exercise our heart rate increases to an average of 140 to 160 beats per minute.  When a bat is flying its heart rate speeds up to 600 beats per minute!

Benefits of Bats

Bats are not only beneficial to the environment, but to humans as well.  Bat guano is the best fertilizer available.  In fact, guano is mined in South America and sold as a valuable commodity!  During the Civil War, soldiers in the South mined the sulfuric content from guano to use as a form of gunpowder.  

Farmers like bats because they eat insects that are harmful to crops.  One bat can eat 1,200 insects in an hour.  There is a colony of Mexican free tailed bats in Texas that consumes on average 200 tons of bugs a night!  When we kill bats, farmers are forced to use pesticides to kill bugs that damage their crops.  When we eat food that has been sprayed with pesticides, the poison is absorbed into our fatty tissue and never goes away.  When you think about, bats help to keep us healthy.  

Bats and Echolocation

Bats make sounds in two different ways.  Orally in the form of a "chirp" and nasally in the form of a click or hum.  The nasal click or hum is very high pitched and is hard for humans to hear.  Scientists think that bats use their nose leafs to send out the clicking sound used for echolocation.  When a bat uses echolocation, the sound travels at ultrasonic speeds and at a very high frequency.  The sound waves hit an object and send back a message to the bat.  Through echolocation bats can tell how far away an object is, it's size, shape, speed, and much more!  

When a bat makes a chirping sound they have a device in their ears that turns off their hearing.  Bats are very sensitive to sound and their own chirping could make them deaf.  Using this device they can turn it off to make a chirp and turn it back on to hear other noises.  

Interesting "Tidbats" of Information

Bat Links