Scientists Not So Chummy in Debate Over Disappearing Great Whites

The facts: great white sharks, which once prowled the waters off the coast of Cape Town, South Africa, by the hundreds, have disappeared from the region. The debate: What drove them off? 

One theory suggests that another coastal predator scared them away. In 2015, marine biologist Alison Kock observed a strange phenomenon. A number of great white carcasses washed ashore or sank to the ocean floor. They were found with wounds slashed along their underbellies and their livers removed. 

"It looked so surgical from the photographs that I first assumed it must have been done by somebody with a knife," Kock told CBS News.

Further investigation revealed that the deep-sea surgeons were a pair of orca whales. The pair had developed a taste for shark livers. "It's the most calorie-dense organ out of the whole body. And it takes up almost a third of the shark's body," Kock said.

Kock and other experts believe that over time, the orcas’ hunting of great whites forced the sharks to leave the coast of Cape Town. Not all experts buy it, though. Some point to human-related causes. That includes longline fishing in the region. Longline fishing has culled many populations of smaller sharks. Those smaller sharks made up a large portion of the great whites’ diet.

"Shark longlining is undoubtedly robbing the great white sharks of food," Christopher Fallows told CBS. He's a shark photographer. "It's the primary prey source for the great whites when they're not feeding on seals." 

No matter the cause, Fallows is worried that the debate may get in the way of protecting the sharks. 

"Let's stop bickering about something we can't control, and let's start focusing on the things that we can control," he told CBS. "If we don't start addressing those factors that we can control, I don't believe there's any hope."

Reflect: What is a problem in the world that you wish more people would work together to solve?

Gif of great white shark from Giphy.