Bottlenose Dolphins

Bottlenose Dolphins is the most common and well-known dolphin species. It inhabits warm and temperate seas worldwide and may be found in all but the Arctic and the Antarctic Oceans.

Bottlenose Dolphins are grey, varying from dark grey at the top near the dorsal fin to very light grey and almost white at the underside. This makes them hard to see both from above and below when swimming. The elongated upper and lower jaws give the animals their name of bottlenose. The real nose however is the blowhole on top of the head. Their face shows a characteristic "smile".

Adults range in length from 6 to 13 feet and in weight from 330 to 1430 pounds with males being slightly longer and considerably heavier than females on average. The size of the bottlenose dolphins appear to vary considerably with habitat. Most research in this appear has been restricted to the North Atlantic Ocean, where researchers have identified two ecotypes. Those bottlenose dolphins in warmer, shallower waters tend to have a smaller body than their cousins in cooler pelagic waters.

For example a survey of animals in the Moray Firth in Scotland, the world's northernmost resident population, recorded an average adult length of just under 13 feet. This compares with a 8 feet average in a population off Florida. Those in colder waters also have a fattier composition and blood more suited to deep-diving.

The flukes and dorsal fin are formed of dense connective tissue and don't contain bones or muscle. The animal propels forward by moving the flukes up and down. The pectoral flippers serve for steering; they contain bones clearly homologous to the forelimbs of land mammals from which bottlenose dolphins and all other cetaceans evolved some 50 million years ago.

Bottlenose Dolphins typically swim at a speed of 3-6 miles per hour; for short times, they can reach peak speeds of 21 mph. Every 5-8 minutes, the bottlenose dolphins have to rise to the surface to breathe through their blowhole. On average, they breathe more often however, several times per minute. Their sleep is thus very light; some scientists have suggested that the two halves of their brains take turns in sleeping and waking.

Bottlenose Dolphins normally live in groups called pods, containing up to 12 animals. These are long-term social units. Typically, a group of females and their young live together in a pod, and juveniles in a mixed pod. Several of these pods can join together to form larger groups of one hundred bottlenose dolphins or more. Males live mostly alone or in groups of 2-3 and join the pods for short periods of time.

The species is commonly known for its friendly character and curiosity. It is not uncommon for a diver to be investigated by a group of them. Occasionally, bottlenose dolphins have rescued an injured diver by raising them to the surface, a behaviour they also show towards injured members of their own species. In November 2004, a more dramatic report of bottlenose dolphins intervention came from New Zealand. Three lifeguards, swimming 100 meters off the coast near Whangarei, were reportedly approached by a 3 meter Great White Shark.

A group of Bottlenose Dolphins, apparently sensing danger to the swimmers, herded them together and tightly surrounded them for forty minutes, preventing an attack from the shark, as they returned to shore. Bottlenose Dolphins are predators however, and they also show aggressive behaviors. This includes fights among males for rank and access to females, as well as aggressions towards sharks and other smaller species of dolphins. Male dolphins, during the mating season, compete very vigorously with each other through showing toughness and size with a series of acts such as head butting.

Female Bottlenose Dolphins live for about 40 years; the more stressful life of the males apparently takes its toll, and they rarely live more than 30 years. Bottlenose Dolphins communicate with body movements and with sounds they produce using six air sacs near their blow hole. Each animal has a characteristic signature sound with which it identifies itself to others. Other communication uses about 30 distinguishable sounds, but a "dolphin language" has not been found.