2x Whales & Dolphins, A collection of twelve Prints, Postcard Packet. Dolphins and whales belong to the cetacean order of the mammal family. Of the 4,060 species of mammals in the world, 85 of these are cetaceans. Like land-living mammals, cetaceans have young that are born alive and suckled on milk provided by their mothers. They also have a relatively high and constant body temperature, and have hair at some stage of their lives-usually in the form of whiskers on the snout of a newborn. Whales and dolphins also breathe air like other mammals, and their nostrils are called blowholes located on the top of their heads to allow breathing while swimming. A collection of twelve Prints, Postcard Packet, Postcard size 4 x 6