Walking shark discovery reveals new species in tiny Papua New Guinea range

Officially called Dudgeon's Walking Shark (Hemiscyllium dudgeonae), the nocturnal species found only in a tiny area off southeastern Papua New Guinea (PNG) was scientifically confirmed in a collaborative paper published in Zenodo

A night dive to study wild sharks that can walk on land has surfaced with something even rarer—a species unknown to science. "New shark species don't come along that often, and it's most definitely the first one named after me," said a surprised Dr. Christine Dudgeon of the University of the Sunshine Coast about the meter-long specimen she caught by hand and carefully guided back to the study boat.

Now officially called Dudgeon's Walking Shark (Hemiscyllium dudgeonae), the nocturnal species found only in a tiny area off southeastern Papua New Guinea (PNG) was scientifically confirmed in a collaborative paper published in Zenodo.

The UniSC-led research team was working in Milne Bay and nearby shallow waters last year to examine numbers of endangered epaulette sharks.

The sharks, which eat invertebrates off the seafloor and are not dangerous to humans, are famous for using all four fins as limbs to amble across reef flats at low tide.

While a related species in the Great Barrier Reef is relatively well studied, the global team focused on understanding the distribution of—and threats to—PNG epaulettes endemic to the tropical waters north of Australia.

UniSC Ph.D. student Jess Blakeway, lead author of the paper, was first to see the specimen in the boat's lights as it was brought in by her supervisor, Senior Research Fellow Dudgeon.

Chris Dudgeon with shark named after her. Credit: Nesha Ichida

"Straight away, I recognized that the color pattern was different from any of the other species I had worked with before," Blakeway said.

"The first thing that stood out was the white dashes along its brown body. These dashes were quite different from the leopard-like spots we were expecting.

"We put it in a tub with fresh seawater to give us time for measuring and blood and tissue sampling, and over the next two nights found another 11 individuals with the same patterning.

"It wasn't until genetic analysis of the samples back in Australia that we could confirm a new species. It's exciting because this is the first new species described for the genus since 2013."

H. dudgeonae was named after renowned elasmobranch geneticist and ecologist Dudgeon, who has researched the genus (group of species) for more than two decades. The new species' local name is kadedekedewa, which loosely translates to dog shark or lazy shark because of its slow, four-limbed gait.

UniSC Ph.D. student Jess Blakeway, Dr. Mark Erdmann and UniSC Senior Research Fellow Dr. Christine Dudgeon with Dudgeon's Walking Shark. Credit: Nesha Ichida

The findings immediately raised concerns about the new shark's vulnerability because of its restricted home range, habitat degradation, fishing activity and climate change.

"We hope to collect more data on our next research trip in October to help the International Union for Conservation of Nature (IUCN) Red List assess the species as vulnerable or endangered with extinction," Blakeway said.

The research also revealed new information about the geographic distribution of two other epaulette species off the island of New Guinea.

Survey methods included diving, snorkeling and reef walking to catch walking sharks by hand, with 70 dedicated surveys completed at 35 sites in 15 locations.

Co-authors included Ph.D. supervisors Professor Kathy Townsend of UniSC and Dr. Mark Erdmann of Re:wild and the California Academy of Sciences, and collaborators Dr. Gerald Allen of the Western Australian Museum and Conservation International, Max Teliwa of PNG's Milne Bay Provincial Fisheries, Julie Waranaka of the University of Papua New Guinea, and William Brooks of San Francisco.

Blakeway said the research also changed the understanding of where walking sharks can be found.

"Previously, it was thought that each species had distinct habitat barriers such as rivers or deep water. Now we know that distributions in eastern PNG overlap, though species do not co-occur.

"The new species is the 10th in the PNG epaulette genus (group of species). Five are already listed as threatened with extinction on the IUCN Red List under criterion B (which relates to their restricted geographic range)—a criterion that only applies to 3% of all sharks."