Men are the cleverest and most dangerous animals on the earth. Rats come second. Men kill many beasts, and they've even killed millions of men since very long ago, but rats kill more men. Rats carry many diseases and these diseases have killed and are still killing thousands and thousands of men today in many countries. Rats are dangerous not only in one way. They not only carry diseases into men's homes, they also eat up men's food. They eat 33 million tons of grain every year. Men starve because rats eat their food. Rats are clever, too. They have good leaders to tell them the food is terrible when men put poison in it. There are a lot of rats in our cities and villages today. We can go to the moon, but we can not kill all these terrible animals. Is this dangerous enemy too clever and grows too fast, or are we not clever enough and not clean enough?

Different animals have different sleeping habits. Some animals stand when they sleep, for example the giraffes. The giraffes sleep very little a day. The elephants only sleep 4 hours a day. Fish live in water. Some fish sleep while they swim. Some birds sleep while they fly in the sky. The tigers like sleeping. They usually sleep for 16 hours a day. Some animals sleep in the day and wake up at night, such as foxes and the owls. The owls catch the mice at night. Everyone needs sleep.

Many people are looking for a pet that is a little more interesting than a cat or a dog. If you have a lot of space and are happy to find out how to look after it, a green iguana（蜥蜴）） can make a great pet. We spoke to Dr. Troy Wilson, a specialist in lizards, about how to look after an iguana.

The first question is, what should it live in?

Dr. Wilson: The green iguana can grow to be about 2 meters long, so you are going to need a big space to keep it in. Start with a small glass tank for a baby iguana, then when it is bigger, you can move it into a larger cage.

Do they need water?

Dr. Wilson: Yes. Iguanas need water to drink and sit in. In the wild they always live near water and they are good swimmers. They need a water dish or small pond that is big enough for them to sit in.

What do they eat?

Dr. Wilson: They eat mostly raw vegetables and some fruit. You can feed your iguana fresh vegetables every day and some fruit once a week. Iguanas cannot chew their food so you should cut it into the right size. They swallow food in one piece.

Are they fun?

Dr. Wilson: An Iguana is a clever, friendly animal. It will learn who you are and can even be quite affectionate. (深情的)