Tuesday, October 2, 2012

Batty For Bats!

October is the month for all things related to Halloween and Kat and I have begun decorating our house in full festive fashion! While we were cutting out bat silhouettes to line our spooky hallway, we began talking about the animals themselves. We knew the basics: they are mammals, they fly, and they use sonar to find their food. Beyond that, we didn't really know much about them. So, for the next two weeks, we learned a lot about bats, played batty games, and even went to a local bat colony!

Bats are really quite fascinating. We've all heard the phrase "blind as a bat", but did you know that it is scientifically inaccurate? Bats can see just as well as humans; they are not blind at all. In fact, many fruit bats and other fruit/nectar eating bats can see exceptionally well, as they use their senses of sight and smell to locate their food. It is the smaller carnivorous bats, who hunt moving prey at night, that rely on echolocation to find their food.






Bat anatomy is also quite interesting. Upon inspection of the skeletal structures, you'll find that there are many similarities between bats, birds, and even humans! For example, if you look carefully at the bat's wing, you can see that the bones inside are simply elongated fingers supporting lengths of stretched skin. Even the bat's name Chiroptera comes from Greek words meaning "hand" and "wing". The skin covering the fingers allows the bat to fly; the fingers are flexible and can individually bend, allowing the bat to quickly change its direction, even when flying at top speed.




Although we typically think of vampire bats or fruit bats like Stellaluna, there are an estimated 1,240 bat species around the world. The sheer number of bats is astonishing. With millions of bats in every species, bats make up approximately 20% of all mammals on Earth! Bats are grouped into two  large suborders, The Megabat (megachiroptera) and Microbat (microchiroptera).




Megabats are usually large and their diets consist of fruit or nectar. They have larger eyes, smaller ears, and a keen sense of smell with which they locate ripened fruit. With one exception, megabats do not use echolocation. These bats are very helpful with seed dispersal and pollination. Incredibly, megabats are responsible for 95% of animal seed dispersal in some rain forests! Many plants specifically rely on bats in order to reproduce. Some megabat species include the Large Flying Fox, Fruit Bats, and the Hammerhead Bat.




Microbats are generally smaller than the megabats. Most microbats are carnivorous, feeding on insects, fish, lizards, amphibians, small birds, other bats, and in the case of the Vampire Bat, animal blood. Microbats have smaller eyes and larger ears. The ears are ribbed with sharp ridges, which focus the incoming sounds so the brain can compile a detailed image of the bat's surroundings. Some species have developed special nose leaves, which they use to produce the bursts of sound in echolocation. This frees the mouth for eating while the bat is flying. Some microbat species include the Mexican Free-Tailed Bat, the tiny Bumblebee Bat, and the Spotted Bat.




Microbats hunt at night and many use echolocation to do that. Echolocation is when a bat (or other echolocating species) calls out a quick succession of chirps, then listens for the sound waves to hit an object and bounce back. When the echoes enter the bats specialized ears, the sound waves are focused so the brain can form a sharp image of its prey's location, distance, and shape.

Some insects have developed defenses against bats and their use of echolocation. Some moths are able to hear as the bat's echolocating calls. If the bat is within striking distance, the moth will begin dodging and diving in an attempt to evade the bat. One species of moth sends out clicks of its own, warning the bats of their bitter taste. Other moths have taken advantage of this and have developed a mimicry of these moths, further confusing the bats.

As moths have developed ways to evade them, bats have come up with counter strategies of their own. Some bats have begun calling at higher and lower frequencies. While changing the frequencies keeps the bat out of range of specific moths, it does limit the effect of the echolocation, allowing details to be given only at specific distances.Other bats have dropped echolocation altogether, using it only to navigate through the branches and leaves. This bat uses its large ears to listen for the sounds of its prey moving or fluttering its wings.

Kat and I played some really fun games to demonstrate the echolocating techniques of bats as well as the evasive measures taken by the moths. These work really well, whether you're playing with a couple of kids, or with a large classroom!




ECHO! LOCATION!

This game is played in a similar fashion to "Marco Polo", where one player is blindfolded while the other players hide around the room. The blindfolded player acts as the bat, and calls out "ECHO!" while the "moths" call out "LOCATION!". The bat then attempts to locate the moths, relying solely on "echolocation".

Variations of the game include:
1. "ECHO!" "ECHO!"
The player acting as the bat will call out "ECHO!" as before, only this time, some of the moths will send out their own calls in return, confusing the bat.

2. "..echo!" "...location!"
Have the bat change the pitch of its echolocating call, in an attempt to silence its calls to the moths that can hear them. The players acting as moths won't be able to call out "location!" until the bat is almost upon them.

WHERE'S THE BAT PUP?

Mother bats give birth to one bat pup per year. They give birth and raise their young in large nursery colonies, where the bats cling to the walls until they learn how to fly. How do the mommy bats know where their specific baby bat is when it's clinging to the walls amongst thousands of other baby bats? The key is in their sense of smell!

Materials Needed: 

1. String or yarn
2. Cotton Balls
3. Essential Oils, Vinegar, Vanilla (we used one scent, if you have a group of kids, use a variety of smells)

Instructions:

1. Divide the kids into two groups. One group will consist of mommy bats, the other will consist of bat pups.

2. Cut lengths of yarn or string to make a long necklace. You will need as many lengths as there are bat pups.

3. Tie the cotton ball in the middle of the necklace. Dab enough essential oil on to the cotton ball to make a very strong smell. Have the bat mothers smell the necklaces of their bat pups so that they will remember the identifying smell of their bat pups.

4. Tie the necklaces around the necks of the bat pups. Then have them hide in the room.

5. Have the bat mothers go look for their bat pups! As they get close to the bat pups, the pups will hold their necklaces up to the mothers so that they can take a sniff. If they find their bat pups they can stand aside and making happy clicking noises to each other until the game is finished.

Kat and I had a lot of fun playing these games. In fact, we're still playing the echo location game! This one was a big hit, one that I think I will use any time we're with a group of kids and we're talking about bats. The best part of our bat adventures however, was our trip to the Phoenix colony of Mexican Free-Tailed bats!


We took a few trips to the bat tunnel, we even brought friends!


The bat colony lives at the 40th St and Camelback Canal tunnel (link goes to tunnel to the left of the soccer field) and is recognized by the Arizona Department of Fish and Game as an official urban bat colony. Because the bat tunnel is off the canal, it is open to the public and during the summer months anyone can go and visit them as they fly out for nocturnal hunting!

Depending on the time of year, the bat tunnel has a population ranging from 5,000 to 20,000 bats! You'll want to arrive just before sunset, so that you can make the 1/4 mile walk in time to see the bats as they leave their roost for the night. We got to share in the thrilling experience of having the bats fly all around our heads as they sought the thousands of insects in and around the canal area!


This kids were really excited as they watched the bats fly around!
Photo Credit: Jenny Davey

The kids (and adults too!) had a wonderful time as we watched the bats fly around and skim the water, looking for drinks and insects. The bat colony migrates south to Mexico in October, so the population has dwindled quite a bit. However, this is something that will surely become an annual tradition for us as we head back to the bat tunnel to watch these masters of flight!


Sunset over the canal. If you look closely, you can see a bat in the lower right corner!
Photo Credit: Jenny Davey

Kat and I both had a great time learning about bats. Not only did we learn about the variety of species and their roles in controlling insect population and seed dispersal, but we were able to spend quite a bit of time among them both in our neighborhood and at the bat tunnel. I'm excited to make this an annual tradition, maybe next year we can bring even more friends with us and have group bat outings! As for now, we'll have a much greater respect for the animals as we continue work on our spooky Halloween hallway...





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