Underwater drones can provide us with unrivalled views of marine life ... but when your subject animal is a top predator with a habit of test-biting anything peculiar in its environment, a harmless pass can turn into an oesophagoscopy before you know it.

Image: OpenROV/YouTube

This inside-out view of a great white shark was captured by OpenROV community member Dominik Fretz in the stunning blue waters off Mexico's Guadalupe Island. Guadalupe is a stopover for some of the largest great whites ever recorded, including famed females "Deep Blue" (6m/20ft) and "Mystery" (5.4m/18ft).

For the protection of these threatened animals – as well as the human divers who come to view them – free-swimming with great whites is typically prohibited near the island. During this expedition, however, Fretz joined a group of experienced local researchers and shark conservationists to capture the iconic animals in the water with minimum disturbance. 

This particular clip was filmed using a Trident underwater drone that had been camouflaged with electrical tape. Team member Dr Mauricio Hoyos Padilla suggested breaking up the tech's silhouette in the hope that the sharks would pay less attention to it. Some great whites swam by without any interaction, while others came in to bump and nudge the drone. One large male, known locally as "Thor", appeared particularly interested.

"The sharks were very curious about the ROV," Fretz wrote in an OpenExplorer field journal update. "[This was a] typical great white shark approach. One moment you don't see him, and you blink, and there is this 16-to-18-foot, three-to-four-thousand-pound predator directly in front of you. Apparently, though, Tridents aren't tasty for sharks and it was spat out again right away." 

Earlier this month, a great white known to local researchers as "Kermit" took an underwater camera for a ride off the coast of New Zealand. That piece of kit was baited with tuna steaks, so the allure of an easy meal may have prompted Kermit's heist. The Trident, however, is not a baited device, so it's possible that electrical signals produced by the small drone drew the sharks in. To its credit, the Trident survived the journey down a white shark gullet with only a few minor bite marks to show for it. 

"The tether wasn't cut," says Fretz. "How, I don't know. The shark was fine too; it went about its business and [came] back a few times."

The Trident drone was developed as a more accessible alternative to traditional ROVs, which are extremely costly. Judging by how well this one held up against such a formidable opponent, researchers like Hoyos Padilla may be using it more often in the future. The drone is controlled from a topside laptop, so it's a great tool for making underwater observations on non-diving research trips as well. In fact, anyone can purchase a Trident (though we don't recommend using your new ocean-exploration toy to conduct dental exams on protected sharks).

With the help of the freedivers on board, the team managed to tag two great whites during the expedition. The information that bounces back from these acoustic transmitters will help us to better understand the movement patterns of white sharks during their stay at Guadalupe, as well as offering clues about how the animals use this swathe of pristine habitat.

"Even from the ROV footage, it was clear why this place is one of the best spots for diving with great white sharks," adds Fretz. "The water is relatively warm and the visibility seems endless. The blue of the water is mesmerizing."

Hammherhead QA-related content-2015-4-14

h/t Southern Fried Science


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