The ancient Greeks believed that hippos were a kind of rough draft of horses, so it makes sense that the god Poseidon had both horses and hippopotamuses under his purview. But modern scientists from the Royal Veterinary College studying video footage of hippos have revealed another connection between the two animals. They have similar gaits.
When hippos run — and they can reach top speeds of over 30kph — they spend a not-insignificant portion of their time with all four limbs off the ground. This puts them in a fairly exclusive club among heavier mammals.
“We were pleasantly surprised to see how hippos get airborne when they move quickly,” John Hutchinson, the lead author of a paper published in the journal PeerJ, told the BBC. “It’s really impressive!”
Impressive indeed. Bull hippos can weigh as much as 4,500kg and stand 1.6m tall. That’s a lot of mass to have all four legs off the ground simultaneously, but hippos do it for as much as 15 percent of their run cycle.
Watching hippo footage, not a bad gig
Hippopotamuses are Africa’s most deadly animals (to humans) because of their size and testy, territorial nature.
“That’s part of the reason why science knew little about how hippos move before our research,” Hutchinson said. “It’s hard to work with hippos as they tend to stick to the water and very seldom are trained to be studied in zoo collections.”
Researchers studied video footage of hippos, like the still shown here, to do their research. Photo: Johan Vermeulen
Video footage to the rescue. Hutchinson and his team studied 169 movement cycles from 32 individual hippos. The result revealed that when hippos run, they move their legs diagonally: front right foot and back left foot, then front left foot and back right foot, and so on — a trot.
This puts them in line with horses and other speedy quadrupeds, as opposed to animals like elephants, which move both left legs and then both right legs. This style of motion means elephants never fully leave the ground.
Even more surprising, hippos trot regardless of whether they move slowly or quickly. Not even horses do that! In fact, most land mammals change their movement style depending on speed.
But hippos are a special case, it seems.
The researchers hope the new study will provide a glimpse under the hood of hippo evolution.
