Since the 1975 film "Jaws", the great white sharks have been considered the most fearsome predators of the ocean. But new research published on Tuesday shows that may not be the case.
When the great white ones that hunted seals near the Farallon Islands, in the outskirts of San Francisco, they found orcas that swam, fled, swam long distances to escape and did not return until the following year, according to a study carried out by researchers from the Aquarium. from Monterey Bay, Stanford University and Point Blue Conservation Science in Petaluma.
"After orcas appear, we do not see a single shark," said Scot Anderson, an expert on white sharks at the Monterrey aquarium.
The great white sharks are incredible hunters. They can grow up to 20 feet long and weigh more than 4,000 pounds. But killer whales are even larger, grow up to 30 feet long and weigh 10,000 pounds or more.
White sharks swim 35 miles per hour, faster than the fastest man in the world, Jamaican sprinter Usain Bolt, can run. But the killer whales swim just as fast, they are stronger and they hunt in groups, like the wolf packs. And they have been documented, sometimes, eating white sharks, even in a famous 1997 incident that was filmed in the Farallón Islands. Two years ago, five dead white sharks washed in South Africa, and were killed by orcas. The killer whales had eaten their livers.
"As incredible as it seems when you see a shark swimming in the 17-foot boat, there's a bigger predator, the orca," said Sal Jorgensen, an expert on white sharks at the Monterrey aquarium, while sailing on a boat in a video . Of the Farallones that the aquarium published on Tuesday on its website. "It's quite humble to see."
Jorgensen was the main author of the article, which was published in the journal Nature Scientific Reports.
From 2006 to 2013, he and other scientists from the aquarium and Stanford University tracked 165 large white sharks with high-tech acoustic markings between the island of Farallon in the southeast, Tomales Point in Marin County and the island of New Year in the county of San Mateo. They attached the small tracking tags with a 10-foot stick and a small titanium dart.
Jorgensen and Anderson compared the behavior of sharks with that recorded in 27 years of records compiled by researchers who observe elephant seals, sea lions and killer whales in the Farallón Islands. The records were compiled by researchers from Point Blue Conservation Science, a non-profit group and other organizations.
The study found that it was rare for killer whales to swim next to the Farallones between September and December, when white sharks are there in large numbers every year to hunt seals. In fact, orcas were there only 18 days in the 27 years during the autumn and winter months.
But when the two fearsome predators overlapped, the white sharks could not escape fast enough. The hunters became hunted.
In the best documented case, killer whales from two different groups arrived at Farallons on November 2, 2009, when 17 previously tagged white sharks were present. The orcas only spent two hours in the area. But the sharks went off. Seven of them swam 50 miles south to New Year Island, while others swam to Tomales Point, 35 miles to the north.
None of the sharks returned until the following year.
According to the researchers, similar examples of "abrupt and consistent flight" of white sharks were found in 2011 and 2013 when killer whales reached the Farallones.
The beneficiaries? Sea elephants and sea lions.
In a typical year, scientists observe that about 40 sea elephants and sea lions are eaten by large targets near the Farallon Islands from September to December. But that number was reduced four to seven times in years when the white sharks fled the killer whales.
Although relationships between large predators on Earth have been studied for years, little is known about how large predators interact in the ocean. Scientists say that white sharks may be fleeing for fear of being eaten. They can also be harbaded by killer whales, which also eat seals and sea lions.
"Normally we do not think about how fear and risk aversion could play a role in shaping the hunting of large predators," Jorgensen said. "It turns out that these risk effects are very strong even for large predators like white sharks, strong enough to redirect their hunting activity to less preferred, but safer areas."
More research is needed, he said.
Until then, the predator of the Pacific coast is not the monster of "Jaws", but the same species that for years performed tricks in Sea World and other marine parks: the killer whale.