Most kangaroos live in Australia, but some are found in New Guinea. Kangaroos eat grass and nuts. They are six to seven feet tall and weigh 100 to 150 pounds. Their tails grow longer than three feet. Kangaroos use their tails to help them keep their balance while hopping. Male kangaroos are called boomers and baby kangaroos are called joeys. Female kangaroos may have babies at any time of the year but babies are usually born when the grass is green. The babies stay in their mother's pouch for about six to ten months then stays with her for about sixteen months. One enemy of kangaroos are humans. An average of three million kangaroos are killed each year by humans. Kangaroos have an average life span of ten years, but may live for up to twenty years.