Batty for Food

Hunting for Insects with Sound

There are a few different ways that bats can hunt or search for food. Some bats just listen for the sounds that insects make in order to find them. Others rely more on vision to find food, such as some fruit bats.

But many bats use something very unique in the animal world to navigate and find food: echolocation. Have you ever shouted in a cave and heard the sound repeat? That repeating sound is an echo. Echolocation is when an animal makes a sound and listens for the returning echo to find out more about its surroundings.

 Think about how we use our eyes to find things. It is easier to find your favorite toy when your bedroom is tidy than when it is very messy, because it is simply easier to see.

Bats that do use echolocation run into some problems similar to when you look for your favorite toy. Echolocating bats that hunt over water (like in a clean room) will be able to easily pick out the echoes bouncing off of insects. But when a bat uses echolocation in a cluttered environment, it will hear echoes from many other things besides insects, such as leaves and branches. There, they have to learn which echoes are from things they can eat. 

What do these differences in habitat mean for the learning skills of bats?

Do Bats That Hunt in Forests Learn Faster?

The researchers caught three species of bats in Bulgaria. The Long-fingered bat hunts over water. The Greater mouse-eared bat does not use echolocation, but listens for insect sounds on the ground in forests and fields to find them. Geoffroy’s bat uses echolocation to find insects around vegetation. 

To test whether these bats could learn simple rules, they were put in a maze with one of their favorite treats—tasty mealworms. The bats had to crawl around the maze to find the mealworms.

The researchers watched to see how long it would take for the bats to learn to crawl directly to the mealworms (see picture of Maze A). This is kind of like if the researchers measured how many times you had to visit a new friend’s house before you could find your way there without making any wrong turns.

The next experiment looked at the bats’ ability to re-learn something. This time, the researchers put the mealworms on the opposite side of the maze (Maze A, the top maze in the image). This is considered a more difficult test, because the bats have to change what they already know and learn to crawl a different route.

Suppose your friend moved to a new neighborhood – you would have to re-learn the new route to their house. In the same way, the bats had to re-learn the new location of the mealworms.

Finally, to test the bats’ ability to learn complex rules, the researchers added two more paths to the maze (Maze B, the bottom maze in the image). In order to get the mealworms, the bats had to make two decisions: they first had to choose to move down one path of the maze, and then change directions to go down another path.

If your friend’s home were only a few houses away, it would be pretty easy to find. That is simple rule learning. If they moved to the other side of town, you would have to remember more complex directions to get there. That is complex rule learning. Once the maze tests were complete, all of the bats were released back into the wild.

Learning in Different Ways

The researchers found that all three of the bat species can learn simple rules in about the same time. They also have the same re-learning ability. However, this was not the case when it came to flexibility.

When the researchers moved the mealworms, it took the Long-fingered bat (that hunts over water) longer to try looking down another arm of the maze to find them. This means that they are not as flexible in their learning ability, because it took them longer to try a different approach to finding food. Imagine if after your friend moved, you still tried to go to their house every day and were surprised that they were not there. This would mean that you were not very flexible in changing what you know, like the Long-fingered bat.

However, when the Long-fingered bats eventually did try looking in a different place and found the mealworms, they were just as good at re-learning as the other bats. This means that once they finally found the mealworms in a different place, they remembered the new location and changed where they would look in the same way as the other bats. The Long-fingered bats differed from the other bats in complex learning. They were not as good at performing complex tasks as the bats that hunt in forests. 

So what does this tell us about learning in general?Animals that hunt in simple habitats learn more simple rules to find food, and tend to stick with what works. Animalsthat hunt in habitats where it is harder to find food are more flexible in changing what they know, and can learn more complicated rules to find food.

We often look at an animal to learn about the environment in which it lives. But this shows us the opposite can also be helpful. The habitat an animal lives in and its food source can sometimes tell us how it learns.

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 Additional images via Wikimedia Commons. Pollen-covered bat by Bobisbob. Flying bat thumbnail by PD-USGov.