While sharks that walk on land may sound like the terrifying plot of a Sharknado movie, a recent study examined a species that truly can move out of water. But it’s hardly a nightmare-inducing skill: The small sharks can scoot about 90 feet across the land.
“They’re not sprinting. There are no ankle-biters coming to get anybody,” biologist Forrest Galante, who was not involved with the new research, told the Associated Press in July. “It’s just this fascinating behavior taking place.”
Called epaulette sharks, these docile creatures pose little risk to humans—but they’re still considered the “toughest shark on the Great Barrier Reef,” Jodie Rummer, a marine biologist at James Cook University in Australia and co-author of the paper, tells USA Today’s Orlando Mayorquin. The species may provide scientists with valuable information about surviving in harsh environments.
In the research, published in Integrative and Comparative Biology in July, scientists studied the mechanics of how these sharks move, comparing their gait as newborns versus as juveniles. They assert that walking on land might be a survival strategy prompted not only by the sharks’ naturally severe habitat conditions, but also by climate change.
"Epaulette sharks live at the extremes," Marianne Porter, lead author of the study and a biologist at Florida Atlantic University, tells Live Science’s Joshua A. Krisch. "If we want to learn what happens to animals under the extreme conditions of climate change, looking at animals already living under these conditions—and understanding how they move and cope—may be the first step."
Epaulette sharks (Hemiscyllium ocellatum) are about 3 feet long with paddle-shaped fins they use to walk, whether across the ocean floor or on dry land. They live in shallow waters amid coral reefs in the western Pacific Ocean around New Guinea and northern Australia. These hardy sharks can survive oxygen deficiency for up to about two hours, which helps them persist in their challenging habitat.
“You might not think of beautiful, tropical beaches as harsh, but in reality, tidepools and coral reef environments are pretty harsh, subjected to warm temperatures when the tide is out and a lot of changes,” Porter tells The Guardian’s Richard Luscombe. “These little sharks can move from tidepool to tidepool, allowing them to access new pools to forage for food, or tidepools with better oxygenated water.”
In the study, scientists hypothesized that changes in the sharks’ body shapes as they grow would affect how they move, per a statement. Newborn epaulette sharks draw nutrients from an internal yolk sac until they’re about a month old, which causes their bellies to bulge. Juveniles, on the other hand, actively forage for worms, crustaceans and small fish, so they’re more slender, the authors write.
"Shape generally impacts the way we move," Porter tells Live Science. "Human babies walk differently to balance their giant heads, and we assumed that baby sharks would wiggle their bodies and move their fins differently to accommodate their giant bellies."
To test their hypothesis, the research team examined sharks during three gaits of the animals in water: slow-to-medium walking, fast-walking and swimming. Surprisingly, they found that markers such as overall velocity, fin rotation and tail beat frequency remained the same for newborns and juveniles.
Further research—including looking into how these sharks walk on land—could provide more information about why these movements don’t change as the sharks age, per Live Science. And, per the paper, future studies could determine how climate change may have impacted these sharks' walking behavior.
“Understanding how these animals do it and how they’re so successful could teach us a lot about what is needed to be able to survive in the future climatic conditions that we’re supposed to see,” Porter tells USA Today.