Bottlenose dolphins carry sponges as tools and sense electric fields with baby whisker pits
Some bottlenose dolphins forage with marine sponges held on their snouts, a skill passed down through generations. Their brain-to-body measure beats chimpanzees', calves are born with whiskers that leave behind electricity-sensing pits, and yet taxonomists still argue over how many species the group contains.
Bottlenose dolphins are toothed whales of the genus Tursiops, familiar members of the oceanic dolphin family. Researchers have tested their mimicry, their handling of artificial languages, their sorting of objects and their ability to recognise themselves. They use tools, pushing sponges ahead of them to reach food they could not otherwise get, and pass such habits on culturally. Their encephalisation quotient, a measure of brain size relative to body, is 5.26, higher than a chimpanzee's.
How many kinds exist is contested. The Society for Marine Mammalogy recognises three species, the common, the Indo-Pacific and Tamanend's bottlenose dolphin, plus subspecies such as a Black Sea form. Others argue for more, including the Burrunan dolphin described in 2011 from Victoria, Australia. Coastal and offshore ecotypes can be genetically distinct even where their ranges overlap. Bottlenose dolphins also hybridise: a cross with a false killer whale, the wholphin, is fertile, and the first was born in 1985. Fossils from Italy show the genus goes back to the Miocene.
An average adult weighs about 300 kg and can exceed 4 metres. The dark back and paler flanks are countershading, a form of camouflage. Individuals can live beyond 40 years, females typically outliving males by five to ten years, though fewer than 2 per cent pass 60. They cruise at 5 to 11 km/h and sprint briefly at up to 35, and can leap 6 metres into the air. The tail flukes and dorsal fin contain no bone or muscle; the flippers steer and hold bones matching a land mammal's forelimb.
Their senses are specialised. Echolocation clicks, beamed ahead, return echoes revealing an object's shape, size, speed and distance. Eyes with a reflective layer and double-slit pupils work both underwater and in air. Smell is poor, since they lack olfactory nerves and the blowhole shuts underwater, but they can taste salty, sweet, bitter and sour.
Source: Bottlenose dolphin
