On a remote outcrop as night fell on the coast of Papua New Guinea on May 3, 2022, scientists encountered something amazing: a walking shark. Using its fins to drag itself, the small, tan-and-black spotted shark crossed a tidal pool that barely held enough water to brush its belly, moving like a heavy sea lion as it dragged its body on the shore.
The creature was an epaulette shark (Hemiscyllium ocellatum), and is unique among shark species in its ability to walk on land. Forrest Galante, conservationist and biologist, recently shared rare images of this unusual species in a new special for Discovery Channel shark week called “the island of walking sharks (opens in a new tab).”
“This is the first time in history that one of the Papuan epaulette species has been documented walking,” Galante said on the show. “It’s so amazing.”
Scientists believe that epaulette sharks, a species found throughout the southern coast of New Guinea and the northern coast of Australia, developed the ability to walk because it helped them search for food in harsh environments. where other sharks could not survive.
“All traits are selected when allowed [a species] to better survive and create an environment where they are safe and can get food,” said Gavin Naylor, director of the Florida Program for Shark Research at the Florida Museum of Natural History in Gainesville. Epaulette sharks, which grow to around 3.3 feet (1 meter) in length, swim in shallow waters Coral reefs hunt crabs and other invertebrates, their favorite food. When the tide goes out, they are perfectly happy to hang out in the tidal pools and munch on these creatures. “But once they’re done, they’re trapped,” Naylor, who wasn’t involved with the TV special, told Live Science. “What the epaulets have learned to do is climb the reef and throw themselves into the next tidal pool.”
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Epaulette sharks can pull themselves up 30m or more across land, Naylor said. And walking with fins is not the only adaptation that allows them to do so; this species can survive when oxygen is scarce, expending up to one hour on earth on a single breath, Live Science previously reported. This ability also helps epaulets thrive in the low oxygen waters of tidal pools.
Epaulette sharks likely evolved the ability to walk over the past 9 million years, scientists reported in a 2020 study published in the journal Marine and freshwater research (opens in a new tab). It’s incredibly fast for sharks; To put that into perspective, hammerhead sharks, one of the youngest groups of sharks, evolved around 45 million years ago, according to the Natural History Museum (opens in a new tab) in London. And epaulette sharks are potentially forming new species at a remarkably rapid rate, Naylor said. Due to the unique mobility of sharks, small populations are often isolated.
“You might have one that’s in one part of the reef and then it decides to go on an Aussie walk,” Naylor said. A river or other geographic barrier may shift just enough to cut off a small group of sharks from the main population. Over time, these populations can become genetically distinct, as their genes randomly mutate and adapt separately from other gene pools, Naylor said.
A big question about these sharks that scientists hope to answer is how a species with so little genetic diversity within populations could produce individuals so different in appearance. The patterns in the epaulette shark’s distinctive spots vary so widely that no individual looks exactly alike, and Naylor and other scientists suspect that the epaulettes can actually morph their color patterns at will.
“We haven’t proven it, but we think it’s happening,” Naylor said.
Originally posted on Live Science.