How would you like to brush a crocodile's teeth? Or give a shark a bath? Cats are well-known for the way they keep themselves clean by licking , but other animals have their own ways to stay clean as well. And tidiness can be important for their survival. Even cockroaches  have to keep their feelers clean to help them into food. Many animals in the wild, such as deer, wolves and bears, have an automatic cleaning system. Insects like to attach themselves to animals to feed on the skin or blood. These parasites  can be unhealthy. But their "host" animals are constantly dropping skin and fur by a natural process. They also like to rub up against trees or rocks to comfort themselves, and this removes additional skin and fur. Along with old fur goes the dirt and parasites living in the fur. While these animals may sometimes take a bath when they enter or cross a river or lake, they don't need the water to stay clean. They don't get sweaty, because they don't have sweat glands  all over their bodies the way people do. Growing new skin and fur is enough to keep them clean. Some animals and birds use dust to get clean. Chinchillas, a kind of small animal that lives in the mountains of South America, have a very fine fur. (They are raised for their fur, in fact.) If they took water baths, they might get too cold. So, instead, they roll around in fine dust, raising quite a cloud as they "bathe". The dust helps to keep their fur and skin dry. This protects them from bacteria and parasites that enjoy warm and wet places. And the fine dust doesn't stick in their fur for long. It falls off or blows away. As for lions and tigers, their rough tongues act like combs and can remove dirt and loose fur. Why is it important for them to stay clean and smooth? It helps them stay cool in very hot summer or feel warm in cold winter. What's the main idea of this passage?
Animals enjoy living in a clean environment. Animals fight against parasites in different ways. Unlike people, animals hate staying in water. For animals, cleanliness is a survival skill.