Dolphins are a widely distributed and diverse group of aquatic mammals. There are 40 extant species of dolphins. Though not quite as flexible as seals, some dolphins can travel at 55.5 km/h (34.5 mph). Although dolphins are widespread, most species prefer the warmer waters of the tropic zones, but some, like the right whale dolphin, prefer colder climates. Calves are typically born in the spring and summer months and females bear all the responsibility for raising them.
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