Great white sharks appear to use darkness and depth to ambush prey, marine biologists have learned, thanks to unprecedented footage by an undersea drone that was attacked nine times by four sharks.

In the 13 hours of footage, the sharks cruise low above the sand, swim up to the robotic vehicle and inspect it from all sides, bump it curiously, and burst out of the blue to seize the drone in their jaws. In research published on Monday in the Journal of Fish Biology, the scientists described the first great white predatory behavior filmed from under the surface.

“Most of what we know from white sharks is from electronic tagging, or from what we see at the surface,” Greg Skomal, a biologist and lead author told the Guardian. “But when these sharks disappear, what they’re actually doing at depth, where they spend their time – we don’t have a sense of that.”

He said automated unmanned vehicles (AUVs) like his team’s let humans observe marine life in comprehensive detail, rather than what scientists can see in the fleeting shark breaches, or their encounters at the surface or through electronic tracking.

From the waters off Guadalupe, an island off Mexico where Pacific white sharks congregate, the scientists observed 10 different individuals, including the 20-foot female named Deep Blue and a local shark nicknamed Bubba. Skomal said that the behavior captured by the drone cameras supports the idea that white sharks dive down as far as 200 meters in order to use light to their advantage.



“If the shark hangs down at a great depth, in the darkness, then its prey swims above it silhouetted and the shark reduces its own likelihood of detection,” Skomal said. “The remarkable new observations indicate that [my colleagues’] hypothesis is correct, and the sharks ambush from the darkness.”

Most surprising to the researchers, Skomal said, was that “the hunter would become the hunted – the AUV was viewed by the shark as potential prey and aggressively attacked”.

Some sharks did not bite but rather bumped the drone, nudging the vehicle with their snout in what the researchers call an “agonistic” behavior – an aggressive or even defensive thump, but not anything like a committed attack. At other times the sharks simply approached the drone to look at it, before moving on along their way.

The AUV also captured sharks swimming close to the bottom when they were in shallower waters, which Skomal said may be “an effort to snatch prey or spook it up from below, or associated with navigation”.

Amy Kukulya, one of the researchers and an engineer with the Woods Hole Oceanographic Institution, said the “groundbreaking” AUV is so far the first way scientists will be able to study white sharks and other animals in the open ocean.



“Not only do we get to see what they are doing, but we also know exactly where they are and collect data about the physical environmental in which they live.”

Although the drone has opened a window into daily life under the sea, white sharks remain mysterious. Decades of research, tagging and diving have done little to answer basic questions about the fish, including what social lives they might have and where they might reproduce.

Around Guadalupe, presumed to be a white shark haven because of the large number of seals that gather there, the drone did not observe any interaction between the sharks.

“They’re arguably the most charismatic, if not the most well-known species on the planet,” Skomal said, “and it’s still one we know remarkably little about some of its most basic natural history.”

He added that the undersea drone technology could help broader studies of marine ecology, sustainable fishing and ocean conservation. “We could apply it to studying hermit crabs as much as to great white sharks.”