You've seen them in zoos, maybe read about them, or have even watched Nat Geo documentaries, but how much do you really know about hippopotamuses? They're hefty, they're dangerous, and they wallow in water every chance they get. But did you know that hippos can run surprisingly fast? And when they do, all four of their feet are in the air.

Two evolutionary biomechanics specialists from the University of London's Royal Veterinary College, John Hutchinson and Emily Pringle, took to the hippo world to uncover some astonishing facts. With the aid of high-speed cameras, they filmed these colossal creatures running at full throttle.

Running speed of hippos

When you think of hippos, you probably envision a substantial, mostly inoffensive-looking creature, spending most of its time submerged in water.

However, these mammals, weighing up to 1,500 kg (3,307 lbs) for males and 1,300 kg (2,866 lbs) for females, are notoriously aggressive and can be deadly towards humans.

Their surprising agility for such massy beings has long been a source of intrigue. Some have even clocked speeds of up to 30 km/hr (18.6 mph).

Trotting, not galloping

How can a creature as hefty as a hippo reach such speeds? To crack this mystery wide open, Hutchinson and Pringle took a trip to North Yorkshire's Flamingo Land resort, high-speed cameras in tow.

They managed to film a whopping 169 running cycles involving 32 individual hippos. Delving into the footage, they discovered that hippos only tended to sprint when chased by another of their kind, a display of dominance.

Furthermore, they found that hippos, in their full sprinting glory, lift all four feet off the ground simultaneously for about 15% of the time they spend running, with each occurrence lasting for roughly 0.3 seconds. Unlike the galloping rhinos, these mammoths were seen using a trotting type gait when running.

Hippos trot underwater

The study expanded its focus beyond just the movements hippos make on land. The researchers discovered that hippos exhibit a similar trotting gait while underwater. Unlike other aquatic animals that swim, hippos are unable to propel themselves through water in the same way.

Instead, they utilize a unique form of locomotion: they speed-walk along the bottom of rivers or lakes. This method of moving gives them the appearance of being undersea runners, efficiently navigating their aquatic environment by walking briskly rather than swimming.

Hefty hippos running at high speeds

The discovery that these massive animals, often referred to as "elephants," can actually become airborne when moving at high speeds on land is a revelation. This marks the first instance where such behavior has been documented.

Specifically, it has been observed that hippos, which can weigh more than 2,200 kilograms (4,850 pounds), are capable of lifting all four of their limbs off the ground while moving quickly. This observation was confirmed and announced in an official statement from the Royal Veterinary College.

To provide a clearer picture, when these hippos pick up speed, they momentarily lift their entire body off the ground during each stride. This phenomenon is akin to how certain fast-moving animals, like cheetahs or horses, have phases in their running gait where all their feet are off the ground.

For hippos, animals typically perceived as cumbersome and slow-moving, this finding challenges previous assumptions about their locomotion capabilities and offers new insights into their physical dynamics and adaptations.

Future research directions

There's much more to learn from these fascinating creatures. Hutchinson's future research could expand to studying baby hippos and baby pygmy hippos, who may have the ability to gallop when they are young but lose this skill as they grow into their substantial adult size.

This study not only broadens our understanding of the hippo's biomechanics but could also inform their management in captivity and aid in monitoring their health for any physical issues.

So the next time you see a hippo, remember, there's more to them than their gentle, water-loving exterior. These creatures have a need for speed!

The study is published in the journal PeerJ.