New analysis of nine species that ‘walk’ by night on shallow reefs shows their range is much smaller than was known

Bizarre “walking sharks” are at a greater risk of extinction than previously thought, with new information about their distribution leading researchers to expect greater efforts to protect them from human threats such as fishing and climate change.

Bamboo sharks include nine species of sharks that swim and “walk” in shallow waters around northern Australia, Papua New Guinea and parts of Indonesia. In 2013 a new species of the genus was found in Indonesia.

They are harmless to humans and are only active at night, when they start to “walk” around shallow reefs, feeding on crustaceans – even sometimes walking out of the water.

Now a review of the nine species of bamboo sharks has shown their habitats are much more restricted than previously thought. The researchers expect the findings will trigger an increase in the conservation status of at least some of the unusual creatures.

Facebook Twitter Pinterest The sharks are active at night, and their walking behaviour makes them a favourite with divers. Photograph: Mark Erdmann/Conservation International

“Each of the nine species are small – less than one metre – charismatic sharks with unique and quite beautiful colour patterns,” says Mark Erdmann from Conservation International and the California Academy of Sciences. “Their walking behaviour makes them a favourite with divers, who will frequently request night dives with the explicit goal of finding a walking shark.”

Until now, it was thought that the various species had large overlapping distributions stretching all the way from northern Australia and Papua New Guinea to the Seychelles in the Indian Ocean and the Solomon Islands in the Pacific.

Erdmann says the new analysis shows conclusively the sharks have a smaller overall range and that the ranges of the nine species don’t overlap. “This obviously has huge conservation implications for the walking sharks,” Erdmann says.

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“Anytime that a marine species is only found in a relatively tiny area, it means it is significantly more vulnerable to extinction than wide-ranging species. Any local threat – whether from fishing, from an oil spill, from rising temperatures, or even from physical destruction from a cyclone or tsunami – has the potential to wipe out the entire population.”

Gerald Allen from the Western Australian Museum says the sharks have an unusual breeding strategy that further limits their range, at least for a while after they hatch. “The female lays a few eggs amongst marine vegetation and these hatch into miniature adults that must forage for themselves and because of their limited swimming ability they are ‘tied’ to the immediate [area] in which they are born without the dispersal capability of most sharks.”

Erdmann says the new information is likely to prompt a reassessment of the sharks’ conservation status.

He says the International Union for the Conservation of Nature could reassess their status in its Red List, with some of the species likely to gain a more threatened status.

The Red List status doesn’t confer any direct protection to animals listed as threatened, but countries and international conventions use it in considering whether to implement greater protections.

If there is economic benefit to local communities via dive tourism, there is often increased awareness Gerald Allen, Western Australian Museum

Erdmann says the researchers are planning on communicating their findings to the Indonesian government and urging it to list the species found there as protected.

Allen says the team will be working with communities that depend on the sharks to encourage greater protection too. “Increased dive tourism is one avenue for their protection and we are personally trying to spread the word about these sharks and their need for protection in the dive industry. Successful dive tourism depends on healthy reefs and if there is economic benefit to local communities via dive tourism, there is often increased awareness and measures put in place to sustain healthy reefs.”

He says the fish evolved their ability to walk because of their feeding habits. “Their mode of locomotion is intimately tied to the exploitation of their food resources and has led to the evolution of walking rather than swimming,” he says.

“They feed mainly on small, cryptic invertebrates that hide in the reef. Walking enables them to methodically search for food in a slow and purposeful manner.”