Tuesday , January 19 2021

Big white sharks really fear an oceanic animal



Ever since the 1975 movie Wilkie, big white sharks are considered the most horrible predators in the ocean. But a new study published on Tuesday shows that it may not be the case.

When the big whites who hunted seals near the Faralone Islands in San Francisco clashed with whale killers, known as orca, swim, flew away, swam long distances to escape and did not return to next year, according to a study by researchers in Aquarium at Monterey Bay, Stanford University and Science to Protect the Sina Point in Petaluma.

"Once an orca arrives, we do not see a single shark," says Scott Anderson, a white shark expert in the Monterey Aquarium.

Big white sharks are amazing hunters. They can grow up to 20 meters and weigh more than 4,000 pounds. But whale killers are even bigger, they grow up to 30 meters and weigh 10,000 pounds or more.

White sharks swim 35 miles per hour – faster than the fastest man in the world, Jamaica sprinter Usain Bolt, can work. But whale killers swim as fast, stronger and hunt in groups, such as wolf packets. And they were documented, on occasion, ate white sharks, including in a famous 1997 incident, which was filmed from the Faran Islands. Two years ago, five dead white sharks were sunk in South Africa after being killed by orcas. Whale killers ate their liver.

"As amazing as it looks when you see a 17-foot-shark swim with the boat, there's a larger predator orca coming together," says Sal Jorgensen, a white shark expert in the Monterey aquarium, while sailing in a video from Farallons that the aquarium announced Tuesday on your website. "It's pretty calm to see."

The port of about 30 killer whales traveled from the Pacific Northwest, was spotted in Monterey Bay earlier this month. (Photo by Monterey Bay Whale Watch)

Jorgensen was the leading author of the paper, which was published in Nature Scientific Reports.

From 2006 to 2013, he and other scientists from the aquarium and Stanford University followed 165 excellent white sharks with high-tech acoustic tags between the island of Fallon Island, Tomales Point in Marine County and the island of Anto Nuevo in the county of San Mateo. They attached small track marks using a 10-meter-long pole and a small titanium dart.

Jorgensen and Anderson compared the behavior of sharks to those observed in 27-year-old records collected by researchers who followed elephant seals, sea lions and killer whales in the Faran Islands. The records were collected by researchers at Point Blue Conservation Science, a non-profit group and other organizations.

The study found it was rare for whale killers to swim past the Farallons between September and December, when white sharks exist in large numbers every year to catch seals. In fact, orcas only had 18 days in 27 years during those autumn and winter months.

But when two awesome predators overlap, white sharks could not get out fast enough. The hunters became hunters.

In the best-documented instance, whale-killers of two separate pieces arrived in Farallons on November 2, 2009, when 17 previously-marked white sharks were presented. Whale killers just spent two hours in the area. But the sharks are strained. Seven of them swam to 50 miles to the south of the island of Anjo Nuevo, while others swam to Tomales Point, 35 miles north.

None of the sharks returns to next year.

Similar examples of the "sudden and consistent flight" of white sharks occurred in 2011 and 2013, when whale killers came to Farallons, the researchers said.

Users? Elephant seals and sea lions.

In a typical year, scientists note about 40 elephants and sea lions eat large whites near Farallon Islands from September to December. But that number was reduced four to seven times in the years when white sharks ran out of the orc.

Although the relationships between large predators on land have been studied for years, little is known about how many predators in the ocean communicate. Scientists say white sharks may be frightened of eating. They can also be harassed by whale killers, who also eat seals and sea lions.

"We do not usually think how fear and risk aversion could play a role in shaping the great hunters they hunt," Jorgensen said. "It turns out that these risky effects are very strong even for large predators such as white sharks – strong enough to divert their hunting activity into less preferred but safer areas."

More research is needed, he said.

Until then, the top predator from the Pacific coast is not a monster in the "Steel", but the same kind that for years has performed tricks in the sea and other marine parks: ork.


Source link