TOEFL Speaking Task 4 Practice 034Science

Narrator:Listen to part of a lecture in a biology class.

Professor:So let's continue the discussion on roosting. That is the resting and sleeping behavior of winged animals. Today we'll talk about roosting behavior in bats, which roost in large groups. Bats roost by hanging upside down with their feet above their heads, from the roofs of caves, from trees, or from undersides of bridges. Their roosting behavior is actually quite important for their survival. How well, bats like other animals need to eat to survive. They feed on a variety of insects which they have to chase and catch in flight, so they must be ready to fly. However, unlike birds, bats are not able to launch themselves into the air. They can't take off from the ground. But remember that they roost in high places. They use their front claws to climb to a high place like the roof of a cave to roost. Because they hang upside down from high locations, they can easily start to fly by simply releasing their grip, letting go of whatever they were clinging to. Then they're immediately in the air, ready to chase, catch, and eat flying insects. In addition, roosting provides a way for bats to hide from danger. It protects them from predators. When bats are resting or sleeping, they can be easily attacked by predators like snakes and cats. Can they defend themselves against these attacks while sleeping? No. This is where roosting helps: by hanging upside down so far above the ground, these predators-snakes and cats-can't reach and attack them, so the bats can rest and sleep safely.