Bats and Echo Locating
Scientists that study bats have grouped them into two large groups and then divide these two large groups into many small ones. The two large groups are, mega bats and micro bats. The big differences are that the mega bats do not live in North or South America, eat almost only fruit or flower parts, usually do not depend on echo-location to find food, and are generally larger bats. Micro bats live all over the world except in Antarctica or in places during the time that area has below freezing temperatures. They are small bats. Although most micro bats are insect eaters, there is some type of micro bat that eats almost any other type of food that is smaller than it is. Some eat mice, some fish, some other bats, some the same foods as the mega bats, flower parts and fruit, and the infamous vampire bats.
The two most unique things about bats is that they can fly and most micro bats find food by echo location. Of these two echo location is what bats are most famous for. Echo location is using sound to find things. Sound moves through the air by wiggling what ever it hits. Even the air has little bits and pieces in it that are move by any sound we make. When sound waves hit something the sound waves can be soaked up and so become quieter, or bounce off things like a ball bouncing off the wall of a room. If we hear the sound that is bounced back we call it an echo. We hear echoes best in a room that has nothing in it, and its walls covered with hard shiny material like tile. It is this sound wave bouncing ability that bats use, but bats can hear these echoes much better than we humans can. When a sound wave bounces off something part is absorbed and part moves back in the direction it came from. The sound wave is changed. It is the changes in the returning sound wave that the bats understand, use to find food and avoid danger.
Learning activity
Materials
Crayons
Scrap white copy paper with a blank side, cut in quarters, 5 ½ by 4 ¼ inches.
Rubbing templates
Rubbing templates can be made by gluing scraps heavier paper onto some of the 5 ½ by 4 ¼ inch scrap copy paper. The heaver scraps can be simple strips cut to different sizes. To some of the strips of paper add a notch.
Set the notched templates aside. Have students turn the other rubbing templates face down and mix them up. Each student then draws a template, selects a light color of crayon, and makes a rubbing. What do they see? The crayon is the sound wave a bat is sending out. The sound wave fills an area. When it hits an object it changes. Part is bounced back towards the bat. It is the change in the sound wave that the bat understands and uses to tell it where its food is and avoid danger.
Add the notched templates face down and mix them in with the other templates. These represent insects. Allow students a certain amount of time to make rubbings. At the end of this time the students count how many insects they have caught.
Learning activity
Materials
Ping pong balls
Several other types of play balls, such as, small rubber balls, golf balls, even marbles. Students will be rolling these balls around the room so think of how much bounce you want your materials to have and what the balls will sooner or later bounce into, get lost only to be under foot at the wrong time.
Large activity area.
Different objects such as small blocks of wood or boxes paper bags, that will act differently when a ball is rolled into them.
Different surfaces to roll the balls over.
Card board tubes from paper towels
One large box for each group of students.
Most young people, and some of us older ones, have not had much practice on how to make a play ball move in a specific direction. Which for this activity is good.
Set up two objects about a foot apart. And have each student roll a ball between these two objects. The students are young bats learning how to use and control their echo locations abilities. With this activity these bats are learning how to control the sound wave they produce.
The balls represent different strengths of sound produced. When all students have rolled their ball between the two objects, allow them to switch balls with another student and repeat. Repeat until everyone has had a chance to roll each ball. Allow students to comment on which ball they like best and why. Place the two objects on different surfaces such as a rug one time and a non rug surface and allow students to roll the balls again then decide which ball they like for which surface and why.
Move the activity to a non rug surface repeat. After each round, narrow the distance between the two objects.
Use the paper towel tubes to make a guide for the ping pong, or golf balls to roll down and repeat the activity with just the ping pong balls and golf balls.
Set up different objects as targets have students use their hands to roll the gulf balls towards the targets. Which allows the student to hit the target more often? Use both ping pong and golf balls.
Bats need their sound waves to bounce off objects and return to them. Move the activity so that students can roll their balls towards a wall. You might like to make some rules that involve controlling the force that students use to roll their balls towards the wall. The object is to get the ball to bounce off the wall and return to the student, not hurt someone or something. If a sound wave comes back to the bat so hard that it hurts the bat the bat would never use it. So the smart bat that has learned to send the most sound waves in the smallest amount of time in an easy predictable pattern.
We know that if you are facing the person that is talking you hear that person best, but you can hear a person that is facing away from you. This means that sound moves away from the source in all directions. Like us, bats are made to travel best going forward, so it is easiest to catch food that is in front of the bat. Because of this the bat concentrates sending and hearing its sound waves returning from things in front of him.
Divide the students into groups. One student in each group moves the box towards the student with the ping pong balls. The student with the ping pong balls moves towards the student with the box and rolls the ping pong balls at the box so that he can catch each ping pong ball on its return bounce.
Being able to hear most of the returning sound waves allows the bat to build a picture of what is in its flight path, be it food or something to be avoided, such as a tree.
Because most bats find food by sound waves bouncing off these food items, they need to concentrate their hearing towards the area in front of them. Therefore the echo locating bats have large ears. They also have facial features that help them direct the sound waves in the directions they need to hear reflections from. So not only do echo locating bats have huge ears for their head size they also have strange noses. Micro bats produce their sound waves from both their moths and noses. It is not understood just how of if all the strange facial designs help with echo location. The facial forms may be more for smelling friends and relatives than food.
It makes sense that a bat can control its sound production to match the distance from food, speed of travel, and knowledge of objects that need to be avoided. To do this a bat does not send out one burst of sound but several as it moves. The returning or reflected sound waves help the bat understand how it must change its flight path to catch the insect or animal it wants to catch.
Like all animals that must hunt their food. A bat must take in more food than it uses as energy. The best thing most micro bats have going for them is that there are more insects in the world than any other type of animal. Still there are times when insects become scarce. Insects do not like cold temperatures. So areas that have months of cold or freezing weather have few bats or have bats that can adjust to the cold in some way. Some fly to a warmer area. Some find a place to stay, called a roost, that is warmer and wait until things warm up. Some are able to slow down their metabolism so they use only a small portion of food or energy stored in their bodies as they wait for the weather to warm. This slowed metabolism rate is called torpor. Some times the state of torpor is for a few days, but they can enter this state for over 100 days. But what ever way the bat uses to avoid the dangers of weather they must have some sort of energy reserve. To extend the this energy reserve as long as possible bats also need a roost that is at a constant temperature or allows them to keep their own body temperatures at a constant temperature, no matter what the weather temperature outside is.
Learning activity
Cards with either gray, white circles or weather symbols on them.
I make my card template by inserting a table into a new document.
I make the cells six lines of text high.
Next I insert circles in all but one row of cells. Each circle row of cells, will have, two cells with single circles, one cell with two circles, on cell with three circles. One half circle rows will have circles filled in with gray. The other rows of circle cells left white In the last row of cells, I draw one sun in each of two cells, and in the other two, one cloud shape per cell. These sun and cloud cells represent days that are either too cold or too hot for bats to hunt food. Your page of cells or cards should have, three rows of cells with gray circles, three rows of cells with white circles, and one row of weather cells. You will need at least one page of cells or cards per three students.
Squares of colored paper about one inch square or so.
Students draw one card per turn. There are two turns per round. At the end of a round the bat with more food, the white circles, then spend energy, the grayed circles stays alive, and can take a colored piece of paper. When the cards have all been drawn the game is over. Which ever bat has the most colored pieces of paper wins. At the end of a round the circle cards are put in a discard stack. Only the colored squares are kept. These represent stored food energy in the bat.
Just like us some days are too cold or too hot to hunt food. If the weather is too cool, a cloud card, then the bat will enter a torpor state. If the day is too hot the bat will need to stay cool and does this by fanning itself with its wings. Either way the bat must use valuable stored energy to stay alive till the next time it can hunt.
Mix the sun and cloud cards in with the food and energy cards, mix them up, stack and start the game.
This time when one of the two cards drawn for a round is a sun or cloud, the other card must be a two circle food card, white circles. One circle is used to keep cool and one to hunt. If the bats other card is just one circle then the bat must hand in one of his or her colored pieces of paper, using up that stored energy to survive.