High-speed hippos can get airborne, says new study

Researchers found that all four of a hippo's limbs leave the ground when they trot at high speeds. (Warren Little / Getty Images via CNN Newsource)

Hippos can get airborne when moving at high speeds over land, according to a new study.

This is the first time that the animals, which can weigh more than 2,000 kilograms (2.2 tons) and spend much of their time in water, have been found to lift all four limbs off the ground when moving quickly, according to a statement from the Royal Veterinary College (RVC) in the UK.

After analyzing videos showing 169 movement cycles from 32 hippos, researchers found that the fastest-moving animals spend around 15 per cent of each stride off the ground.

John Hutchinson, study lead author and a professor of evolutionary biomechanics at the RVC, told CNN that very little was known about the way that hippos move on land.

“Hippos were a big missing part of the puzzle,” he said. “They’re really hard to study.”

Not only do they spend a lot of time in water, they are “very aggressive and dangerous” and are more active at night, said Hutchinson.

In the videos studied by researchers, hippos tended to move fast when something motivated them, such as chasing a rival hippo or being chased by lions or rhinos, he said.

The team also found that hippos almost exclusively trot – with two diagonal limbs moving in the same direction at the same time, and then the two other diagonal limbs – no matter what speed they are moving at, whereas other mammals such as horses switch from a walk to a trot to a gallop depending on their speed.

“Hippos are one of the very few four legged animals at all that just trot,” said Hutchinson. “That was a pretty neat finding.”

The results could help inform the way that hippos are kept in captivity, as well as helping to detect and monitor whether hippos are suffering physical issues, said Huntchinson.

One sample video that showed a baby pygmy hippo galloping has provided Hutchinson with a jumping off point for future research, he said, adding he wants to investigate whether small hippos, such as baby hippos and baby pygmy hippos, are able to gallop but lose this ability when they grow.

The study was published Wednesday in the journal PeerJ.