The great white shark is one of the largest predatory fish in the world, weighing up to 2,400 pounds, and can grow up to 21 feet in length. It was long thought to have no predators. That is, until Salvador Jorgensen, a marine ecologist, and his team, discovered that the great white shark competes with a vicious enemy - Orcinus orca - also known as the killer whale.
Salvador Jorgensen is a marine ecologist for the Monterey Bay Aquarium where he has been studying great white sharks for almost 16 years. To accomplish this, he and his team would lure sharks by cutting up pieces of carpet to look like seals. Then they would shoot the sharks with electronic tags that emit ultrasonic waves so that underwater receivers could detect the waves as the sharks swam by, making it easier for the team to track them. In 2009, the team tracked 17 sharks that were hunting elephant seals around the South Farallon Island. However, the hunting ended abruptly when two pods of orcas swam past the island. Within eight hours, all 17 sharks had disappeared and didn’t come back for months. Some didn’t come back at all. At first, Jorgensen thought it was a one-time event. But, eventually, he noticed a pattern: orcas would arrive and sharks would leave.
The media portrays orcas as friendly, lovable creatures, but that’s not the case when hunting for food. Toby Daley-Engle, a shark expert at the Florida Institute of Technology said, “[Orcas] have a lot of social behaviors that sharks do not, which allows them to hunt effectively in groups, communicate among themselves, and teach their young.” For example, in October 1997, vessels near the South Farallon Island witnessed a young great white shark interrupting two orcas eating a sea lion. One of the orcas slammed into the shark, killed it, and proceeded to eat its liver. Some recorded cases mention that orcas use a predatory technique where they hold the shark upside down, which causes them to go into tonic immobility, a state of paralysis.
Orcas do not have to kill many sharks to drive them away. Their presence and scent is enough to create a “landscape of fear,” a fear so deep that it changes the behavior of their prey, causing them to flee when they sense the presence of orcas. Other animals, such as dogs, can also create an atmosphere of dread. For example, the sound of a dog can keep raccoons off a beach. This landscape of fear creates a safer environment for the community of animals that live there.
Ultimately, great white sharks are amazing ocean predators, but they know when to leave a losing fight. Ed Yong, a staff writer at The Atlantic, sums up the powerful effects one species’ presence can have on another species. “The fear of death can shape the behavior of animals more than death itself,” Yong said.
[Source: The Atlantic]