Cheerful dolphins

Dolphin

Dolphins are highly intelligent marine mammals and are part of the family of toothed whales that includes orcas and pilot whales.

• They are found worldwide, mostly in shallow seas of the continental shelves, and are carnivores, mostly eating fish and squid. Dolphin coloration varies, but they are generally gray in color with darker backs than the rest of their bodies.

Top ten dolphin facts

• There are currently 42 species of dolphins and seven species of porpoises.
• Dolphins are marine mammals. They must surface to breathe air and give birth to live young.
• A dolphin pregnancy last between nine and 16 months. The mother feeds her offspring on milk. The sons and daughters of resident orcas stay with their maternal family for life.
• Dolphins eat fish, squid and crustaceans. They do not chew they food but may break it into smaller pieces before swallowing.
• All dolphins have conical-shaped teeth. A Risso's dolphin has 14 while a spinner dolphin can have 240.
• The orca (killer whale) is the largest dolphin. Hector's dolphin and Franciscana are two of the smallest.
• The four river dolphin species inhabit the large waterways of Asia and South America.
• Dolphins have an array of vocalisations such as clicks, whistles and squeals which they use for their well-developed communication and echolocation skills.
• Lifespan varies from around 20 years in the smaller dolphin species to 80 years or more for larger dolphins such as orcas.
• Maui's dolphin (a sub-species of the New Zealand dolphin) is the most endangered dolphin. There are less than 50 individuals remaining. Fewer than 10 vaquitas (a species of porpoise) survive.

• Dolphins live in the world’s seas and oceans and in some rivers too. Some dolphin species prefer to live in coastal areas, others like shallow water but prefer to live away from the coast close to patches of shallower water which are located further out to sea.

The fastest dolphin

• Dall’s porpoises are very speedy swimmers; they can reach up to 35mph (56kph). When they swim at high speeds, they create unique fan-shaped splashes of water, called "rooster tails" and this is used to identify Dall’s porpoise at sea.

Orcas are also extremely fast swimmers and probably the only dolphins to reach speeds similar to Dall’s porpoise

Threats

• For centuries, people have hunted dolphins for their meat and blubber. Today, their main threat comes from being caught accidentally in commercial fishing nets. Dolphins must rise regularly to the surface to breathe - becoming entangled in nets prevents this, leading to drowning. For maine dolphins, warming ocean temperatures because of climate change have caused some of their primary food sources to move into deeper, cooler water. Furthermore, marine heatwaves, also caused by climate change, appear to have a negative affect on dolphins' reproductive rates and ability to survive.

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