Dolphin is the popular name for an aquatic mammal in the subfamily Cetacea. The word dolphin generally refers to both the genus Dolphin and the extinct placental group members Lipotidae, which are the modern day breeds of these animals. There are presently forty extant species still living. Five species are fully accepted as valid species in the genus Diathermyellidae.
Among these, the Stymphalian (including the common swamptail) and Humphead (called the sleeper) are two of the most numerous. There are also many species of Cetacea, including the large common dog-fish, the flatfish, the river eel, the common bullfish, and the bottlenose dolphin. Among these, the Stymphalian and Humphead have populations in the southern part of Australia and South Pacific, while the other species are distributed all over the world. All the species share a common habitat: the coastal flats, estuaries, bays, and rivers. In this regard, there are also some differences. For instance, the Stymphalian has a dorsal fin, which does not exist in the other species.
These creatures belong to the dolphin family, Cetacea, and they differ from whales and dolphins in several aspects, including reproduction, diet, status on the food chain, and social organization. For instance, unlike whales and dolphins, which reproduce by being born, the females of this family reproduce by giving birth. Moreover, unlike dolphins and even men, whose spermatozoa stay in the bladder until birth, the females store the sperm until birth. This is why it is called a ‘bladder’ and not a ‘kettle.’ Bladder feeding is a very important function in the reproductive cycle of these mammals. But the females also help to care for their young by swimming with them in a calmer environment – unlike the case of the male dolphin, whose job is to hunt prey with his sperm in the water.
Unlike porpoises and bottlenoses, which are the only marine mammals that are classified as true aquatic mammals, the Stymphalian and humpback are semi-aquatic. They are the only ones among the living beings that are fully developed when they are born, with the exception of the platypus (which is covered with fur). Thus, they retain all the features of the aquatic animal and, except for the presence of gills, are adapted to live exclusively in water.
There are three basic types of dolphin – the bottlenose, the black, and the blue. Among the bottlenose dolphin, the Emeca species is the best known, being recognized as a member of the subfamily Cetacea. The other two dolphin subspecies in the subfamily Cetacea are the Western and Eastern Equine. The Emecas are the only dolphin subfamily that breed at sea, while the other species stay in freshwater. Bottlenose dolphins are the only species of dolphin that breed in fresh water; they give birth to their young in fresh water, being fed with fish and squid.
False killer whales, the smallest of the large cetaceans, are the most endangered of all dolphin species. Although they have fewer numbers than the eastern or white whales, the false killer whale is unique among all other dolphin species in their massive physical size and unique hunting apparatus, the dorsal fin. This fin is used as a weapon against smaller prey, including humans. When they hunt, they often follow ships or boats using sonar, to locate their next meal.
Although the Emeca is the smallest dolphin species and the rarest of the dolphin species, the bottlenose dolphin, the black-tipped dolphin, the Blue-tipped dolphin, and the red-tipped dolphin all belong to the same subfamily. All these dolphins live in tropical and subtropical environments; they feed on a variety of foods including fruits, seeds, small fish and other marine mammals, such as seals and their meat. In fact, they have very similar diets to the large cetaceans. They also like to take mud baths, where they slough off the upper layer of skin to make themselves more slippery.
The smallest dolphin in the world is the Emeca, which weighs around thirty pounds. They live in warm coastal areas and feed on vegetation, fish and crustaceans. They have yellowish color bodies and long streamlined tails. Bottlenose dolphins, the smallest dolphin species in captivity, is the smallest of the twelve types of dolphin in the world. These dolphins are not as friendly as the other dolphin species, although they are playful and have a gentle personality.