There are many different types of bats in the world. Over 900 species have been discovered already. Most bats typically eat fruits,
flower nectar, insects, vertebrates, and some even eat blood. Well over half of the bat populations eat mainly insects. Most bats are nocturnal and use the night’s darkness to hunt, forage, and feed. Their days are spent sleeping, grooming, and resting.
Bats are extremely fast and trying to watch one catch its prey for dinner is particularly difficult. Sometimes bats will eat their insect as soon as they catch it. But they typically will take the meal back to their roost to eat where they can carefully devour the feast without dropping anything. What is so fascinating about these creatures, though, is the way they hear and see.
These creatures use the sounds they make to create an image of the environment in their heads.That is right; bats characteristically use sound to navigate in their surroundings.With this technique bats have found ways to forage for food as well as not bump into things while flying and moving around. Bats make three very distinct echo-locating pulse harmonics at 90, 60, and 30 kilohertz. This process is called echolocation.
Echolocation is the method of hearing that over half the bat populations rely on to see their environments. Such bat calls are typically ultrasonic and have been known to range from 20 – 200 kilohertz. A human’s hearing is maxed out at 20 kilohertz, but you can still hear some form of echolocation clicks from specific bat species. Try smacking two round stones together and listen to the sound. This is what the bat clicks from the echolocation sound like to human ears.
The bat’s sound comes from its larynx and generally escapes from the nostrils or mouth. While the bat makes these high pitched sounds it protects itself by contracting the middle ear muscle and reducing the noise sensitivity. Next the middle ear muscle will relax a few milliseconds later and the bat then receives its echo. The echo tells the bat’s brain what the surroundings look like, from distinguishing multiple animals to seeing whether the tree bark is smooth or soft.
Types of Bats and Hearing
Different species of bats produce different kilohertz of sound. The calls from bats are categorized by intensity, frequency, and
duration. For example the Little Brown Bat sends out such a loud sound that if that sound stimulated a human’s ears the person would be hearing impaired for the rest of his or her life. Other types of bats are born with specialized megaphone noses which help with emitting their echolocation. The Old World Leaf-Nosed and Horseshoe bats both have the specialized nose for echo calls.
- Conrad, Jim. (21 June 2009) Jim Conrad's Naturalist Newsletter. Brown Bats.
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