[ad_1]
Just when you think the orcs could not be more impressive, they get even better. New evidence shows that these whales are really good at scare the most dreaded beast of the sea. Yes. Orcs toppled the great white shark from their "main predator" throne.
A team of marine scientists discovered that great white sharks (Carcharodon carcharias) will be extremely rare each time they detect the presence of orcas (Orcinus orca).
"When they are faced with killer whales, white sharks will immediately leave their favorite hunting spot and will not come back for a year, even if they just pass 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 marked GPS between 2006 and 2013; and 27 years of data on the population of killer whales, sharks and seals collected by Blue Point Conservation Science in southeastern Farallon Island, off the coast of San Francisco.
The team also documented four encounters between great white sharks and killer whales in the Grand Farallones National Marine Sanctuary, which they then analyzed against other data.
The data revealed that whenever killer whales appeared in the area – as always – the sharks came out quickly, stayed to the left and stayed away until the next season. They would choose to leave in a few minutes, even when the killer whales stayed for less than an hour.
And there was a surprising beneficiary: the elephant seals (Mirounga angustirostrous) who live on the coast and fall prey to great white sharks.
"On average, we document about 40 episodes of elephant seal predation by white sharks in southeastern Farallon Island," said marine biologist Scot Anderson of the Monterey Bay Aquarium . "After the killer whales have come out, we do not see a single shark anymore and there are no more victims."
It is also known that transient killer whales eat elephant seals, but these visiting whales rarely occur. Resident killer whales feed on fish.
Sharks do not always go far. Sometimes they only moved a safe distance along the coast, where they were close to different elephant colonies. Sometimes, however, they were heading to the middle of the Pacific Ocean, the area nicknamed the White Shark Café.
They are not tiny sharks either. Some of them measure more than 5.5 meters (18 feet) from nose to tail and are probably quite accustomed to making their way wherever they go. But the 5.5 meters are small enough for orcas, which can attack whales much larger than these, so it is unlikely that they are easily moved.
In addition, killer whales have been observed hunting great white sharks around the world, including near the Farallon Islands. We still do not know why, but sharks killed by a killer whale who fail on shore (one of them is described at the top of the page) lack their liver – their delicious livers rich in oil, rich in vitamins.
That sharks instinctively avoid predators that can eviscerate them so easily, however, or that passing travelers have in the past prevented sharks from moving away from the elephant's food source, remains a stranger.
"I think that shows how food chains are not always linear," said Jorgensen.
"The so-called lateral interactions between top predators are quite well known on Earth but are much more difficult to document in the ocean, and as this rarely happens, it may take a little longer to fully understand. The dynamic."
The research was published in the journal Scientific reports.
[ad_2]
Source link