Just when you think the killer whales could not be more impressive, they get even better. The new evidence shows that these whales are really good at scaring the most feared beast in the sea. Yes. Killer whales have knocked down the great white shark from its throne "apex predator".
A team of marine scientists has found that the great white sharks (Carcharodon carcharias) will become extremely scarce when they detect the presence of orcas (Orcinus orca).
"When faced with killer whales, white sharks will immediately abandon their preferred hunting ground and will not return for up to a year, although orcas are only pbading by," said marine ecologist Salvador Jorgensen of the Monterey Bay Aquarium.
The team collected data from two sources: the comings and goings of 165 large white sharks with GPS tagged between 2006 and 2013; and 27 years of population data on killer whales, sharks and seals collected by Point Blue Conservation Science in Southeast Farallon Island, off the coast of San Francisco.
The team also documented four encounters between great white sharks and killer whales at the Farallones de Gran Farallones National Marine Sanctuary, which they were then able to badyze in comparison with the other data.
The data revealed that every time the orcas appeared in the region, as in each time, the sharks left quickly, the stage abandoned and they stayed away until the next season. They left in a matter of minutes, even when the killer whales were suspended for less than an hour.
And there was a surprising beneficiary: the elephant seals (Mirounga angustirostrous) that inhabit the coast and are prey to the great white sharks.
"On average, we documented about 40 elephant seal depredation events for white sharks in southeastern Farallon Island each season," said marine biologist Scot Anderson, of the Monterey Bay aquarium. "After the orcas appear, we do not see a single shark and there are no more deaths."
It is also known that transient orcas eat elephant seals, but these visiting whales only appear infrequently. Resident killer whales feed on fish.
Sharks did not always go far. Sometimes they just moved a safe distance along the coast, where they were close to different colonies of elephant seals. Sometimes, however, they were heading to the middle of the Pacific Ocean, the region called White Shark Café.
These are not little sharks either. Some of them measure more than 5.5 meters (18 feet) from nose to tail, and are probably quite used to making their own way wherever they go. But 5.5 meters is small for killer whales, which can hunt whales much larger than that, so they are unlikely to be easily pushed.
In addition, orcas have been observed hunting great white sharks around the world, including near the Farallón Islands. It is still not clear why, but the killer whale sharks washed on the shore (one is seen at the top of the page) are missing their livers: their delicious livers, rich in oil and with many vitamins.
However, it is not yet known if sharks are instinctively avoiding predators that can eviscerate them so easily, or if transients in the past have removed sharks from the food source of the elephant seal.
"I think this shows that food chains are not always linear," Jorgensen said.
"The so-called lateral interactions between major predators are well known on Earth, but they are much harder to document in the ocean, and because this happens infrequently, it may take us longer to fully understand the dynamics."
The research has been published in the journal. Scientific reports.