What is the top speed reached by a dolphin?

Dolphins are the sprinters of the oceans. Their streamlined outline, their unusual skin and their powerful muscles make them elite swimmers, able to reach speeds well beyond those of most pleasure boats. But what is the actual record, and what are the biological reasons that make such performance possible?

The champion: the short-beaked common dolphin

The speed record holder among the dolphins is the short-beaked common dolphin (Delphinus delphis), a relatively modest species in size (about 1.80 metres, 75-80 kg). It can reach bursts of 60 km/h, and some exceptional observations even mention 65 km/h. It is the fastest cetacean species known.

For comparison, that is faster than most fast fish, faster than a cheetah over short distances when scaled to body mass, and faster than the majority of recreational speedboats. The common dolphin is quite literally a biological torpedo, optimised by 50 million years of evolution to cut through water with a minimum of resistance.

The secrets of this performance

Several adaptations converge to make this speed possible. First, the hydrodynamic outline: the body of dolphins presents a minimum-drag profile, calculated by naval engineers as one of the most efficient shapes possible. The skin itself is smooth and has unique mechanical properties.

The skin of dolphins is particularly remarkable. Elastic and able to damp the microturbulence that forms at its surface, it reduces friction with the water significantly, and some studies suggest a reduction of up to 80% compared with an equivalent rigid surface. Biomimetics has long been interested in this property with a view to developing hydrodynamic hull coatings.

The musculature is optimised as well. The dorsal and caudal muscles of dolphins are extremely powerful and arranged in bundles that maximise the energy yield of each beat of the tail. The vertebral column, which is very flexible, allows a wide range of movement. And the subcutaneous blubber plays an unexpected propulsive role: through its elasticity it stores energy at each flexion and returns it to the opposite movement, like a spring.

A sprint speed, not a cruising speed

An important point: the 60 km/h is a top speed, reachable over short distances only, a few minutes at most. The cruising speed of common dolphins during migration or prolonged hunting is markedly more modest, around 10-15 km/h. It is the biological equivalent of the distinction between sprint speed and endurance speed in an athlete.

Peak speeds are generally observed during hunting, when the dolphin is pursuing fast prey such as a tuna or a bonito, or while surfing the bow waves of ships, a play behaviour in which the dolphin uses the energy of the water displaced by the boat to propel itself with minimal effort.

The other fast swimmers

The common dolphin is not alone among the fast cetaceans. The killer whale (Orcinus orca) reaches about 56 km/h in a sprint, despite its mass of several tonnes, a performance all the more impressive given its size. Dall’s porpoise (Phocoenoides dalli), a North Pacific species, is credited with bursts of 55 km/h. The sei whale (Balaenoptera borealis), nicknamed the “cheetah of the seas”, is the fastest of the large mysticetes with documented bursts of 50-55 km/h over short distances, extraordinary for an animal of 20 metres and 20 tonnes.

At the other end of the spectrum, humpback whales, blue whales and grey whales have markedly more modest top speeds (15-25 km/h), their mass making acceleration costly. The harbour porpoise, despite its small size, is relatively slow (15-20 km/h), and its survival strategy rests more on acoustic discretion (very high frequency clicks inaudible to killer whales) than on speed.

A remarkable energy efficiency

Beyond raw speed, dolphins stand out for their energy efficiency. The energy cost of travel, relative to body mass, is one of the lowest in the animal kingdom, well below that of the fastest fish. This efficiency also explains why dolphins can travel long distances without exhausting themselves, sometimes accompanying ships for hundreds of kilometres in order to save energy by surfing the bow waves.

To understand how all these factors combine, bioengineers have spent decades studying dolphins. Their outline still inspires the design of submarines, of torpedoes and even of some Olympic swimming equipment. Nature, in its evolutionary patience, has optimised a solution that our technologies still struggle to match.

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