They are marsupials. They are the only large mammal that can hop. They live in groups called mobs. Males are called bucks. Females are called does. Babies are called joeys. Joeys are the size of a jellybean when they are born. They are pink, blind and hairless. They live in their mother's pouch drinking her milk. When they're about a year old they don't need mum's milk any more – but they stay close to her as they still have a lot to learn. Kangaroos are herbivores. They eat only grasses, leaves and the shoots of small trees. As they do most of their feeding in the evening or at night they are nocturnal animals. How do kangaroos keep cool? They rest in the heat of the day. They pant like a dog. They dig shallow holes under trees and lie in the cool sand. They have a spit bath by licking their arms. Kangaroos are very good swimmers but they will only take to water when chased or if they have no other choice. They have very good hearing, eyesight and sense of smell. Why don't joeys fly out of mum's pouch when she's hopping? The female kangaroo can control the muscles that control the size of her pouch and the size of the opening. She can contract the muscles, pulling the pouch tight against the body. If she wants to clean her pouch and wants the joey out, she can also relax the opening allowing the joey to fall out. The milk joeys drink is very different from the milk we drink, so if you ever find a sick joey, never feed it cow's milk.