At night, bats fly through the air, catching hundreds
of insects and other small animals. But during the day, they hardly move at
all. Instead, bats pass the time hanging upside down from a secret spot.
There are a couple of reasons why bats rest this way.
First of all, it puts them in a position for takeoff. Unlike birds, bats can’t
fly into the air from the ground. Their wings don’t produce enough lift to take
off from a dead stop, and their hind legs are so small and underdeveloped that
they can’t run to build up the necessary takeoff speed. Instead, they use their
front claws to climb to a high spot, and then fall into flight.
During the hours when most enemies are active, bats
gather where few animals would think to look and most can’t reach. This allows
them to disappear from the world until night comes again. There’s also little
competition for these resting spots, as other flying animals don’t have the
ability to hang upside down. Bats have a unique physiological adaptation that
lets them hang around this way without using any energy. For you to hold your
fist around an object tight, you contract(緊縮) several
muscles in your arm, which are connected to your fingers by tendons(腱);as one muscle contracts,
it pulls a tendon, which pulls one of your fingers closed. A bat’s talons(爪) close in the same way, except that their tendons are
connected only to the upper body, not to a muscle. To hang upside down, a bat
pulls its claws open with other muscles. To get the talons to take hold of the
surface, the bat simply lets its body relax. The weight of the upper body pulls
down on the tendons connected to the talons, causing them to hold tight.
Therefore, the bat doesn’t have to do anything to hang upside down.
1.Bats
hang upside down because________.
A. they haven’t developed a pair of strong claws
B. they can’t start to fly from the ground directly
C. they have no hind legs to support their body
D. they can’t find quiet places to stay during the day
2.The
third paragraph tells us that bats’ hanging upside down_______.
A. is to save their energy for night movement
B. is a way to fight against flying animals
C. is a great way to hide from danger
D. is a skill to compete for the flying places
3.Why
can bats hang upside down easily?
A. Because their upper body is light.
B. Because they have strong muscles.
C. Because their talons are linked to muscles tightly.
D. Because their tendons are linked to their upper
body.
4.What
is the passage mainly about?
A. The living habits of bats.
B. How and why bats hang upside down.
C. The importance of bats’ hanging upside down.
D. How bats use their energy at night.