There are 30 species of dolphin although not all of them live in the sea. Some are river dolphins that can be found in India, Pakistan, China and Brazil. The largest of the species is the bottled nose dolphin which can grow to over 9ft and weigh 200kg. The smallest species are buffeo dolphins they can grow to 3.9ft and weigh 30kg.
Dolphins are mammals, not fish, and can live up to 40 years but on average 20 years. They need to keep a high body temperature and come to the surface every two minutes for oxygen.
Dolphins feed on shrimp, eels, squid and a variety of fish. Dolphins are predators and feed on live food.Pregnancy usually lasts a year and will produce only on calf; the calf born is almost half the length of the mother and can swim immediately. Matured dolphins give birth every two to four years. Dolphins are very sociable and live in groups called pods.
The greatest threats to dolphins are getting caught in the fishing nets. An estimated 10,000 are killed every year due to fishing equipment. As they are caught in the net they cannot reach the surface to breathe.
Pollution is also a great threat as the fish they feed on can sometimes be contaminated with chemicals; this can kill them or make them unable to breed.
Dolphins are clever, social and curious animals. There have been many stories in the newspaper about whales stranded in shallow water because of how much they weigh and humans are unable to help them. Dolphins have been known to aid stranded whales by pushing them back out to sea.
Dolphins were once hunted for the small amounts of valuable oil extracted from parts of the head to lubricate delicate watch specimens. Dolphins are no longer hunted for this reason as cheaper alternative sources have been found.
Pet dolphins adapt well to human companionship and are easily trained. Bottle nosed dolphins have become well known performers in many aquariums; they are capable of spectacular tricks and may mimic the sounds of a few human words.
Dolphins are wild, intelligent and inquisitive mammals. Dolphins face a multitude of dangers, such as fishing, pollution, collisions with ships, entanglement in fishing gear and habitat degradation.