This curiosity led researchers at the Royal Veterinary College in North Mymms, Hertfordshire, to painstakingly examine footage of hippos. Their analysis revealed that when these large herbivores reach their top speed, they do indeed lift off the ground.
Video evidence showed that hippos had all four feet off the ground simultaneously up to 15% of the time when running at full speed, often in pursuit of chasing away rivals.
This discovery fills a gap in scientific knowledge and positions hippos between elephants and rhinos regarding the athletic abilities of some of the heaviest land animals when they need to move quickly.
“I’ve struggled to work on hippos before because they’re so hard to access,” said John Hutchinson, a professor of evolutionary biomechanics who led the research. “They’re incredibly dangerous, mostly active at night, and spend a lot of time in water.” Finding no satisfying answer in the scientific literature, Hutchinson sent a student, Emily Pringle, to Flamingo Land resort in North Yorkshire, where hippos have space to run. She recorded the animals as they moved between their stable and watering hole and brought back the footage for analysis.
The researchers meticulously reviewed this footage, along with additional videos from YouTube, frame by frame to determine if hippos ever had all four feet off the ground simultaneously. In their publication in PeerJ, they concluded that unlike other large mammals, hippos typically use a trotting movement regardless of speed but can become airborne when rushing.
Other large land animals move differently. Elephants maintain a walking gait even at high speeds and never fully leave the ground. Rhinos can walk, trot, and even gallop. The hippo footage showed that these animals, which can weigh over 2,000kg, generally trot, a movement involving diagonally opposite legs moving in synchrony.
“It’s important for our understanding of what it means to be a big animal moving on land,” said Hutchinson. The research also helps scientists piece together the evolution of locomotion in large land animals, tracing back to the giant dinosaurs.
Hutchinson noted that while the study was “as simple as biomechanics research can get,” it had its challenges: going through stacks of videos frame-by-frame was tedious. “It’s mind-numbing,” he said. “It’s one of the things in my work that I hate the most. It’s really boring. Agonizing.”
Nonetheless, further research calls. Hutchinson has heard that pygmy hippos, a different species, can gallop. This raises the question of whether baby hippos can do the same, suggesting a return trip to Flamingo Land might be necessary.
“I’m wondering if baby hippos can do something that adult hippos can’t,” he said. “That would be pretty neat.”