Tim Harris 
Dolphins [PDF ebook] 

Why do some animals gather in family groups? How do they behave when they are in these groups? These and many other animal behavior questions are answered in these fascinating books. Dolphins are perfectly suited to a life in water, where they eat, sleep, talk to each other, and give birth to their calves. The babies feed on their mother’s milk, and "aunts" help out if mom is busy. Dolphins live mostly in groups called schools.