Science and TechAnimals and Insects


Study: Sharks pull a fast one on liver-loving orcas, migrate to safety

Scientists discovered that great white sharks that disappeared in South Africa didn't die off as speculated; they migrated to avoid orca persecution.
A great white shark.
Posted at 2:58 PM, Sep 28, 2023

Orcas are skilled at hunting great white sharks to primarily consume their livers.

For years, great white shark carcasses washed up on South Africa's False Bay and Gansbaai shores in the Western Cape.

But then, between 2015 and 2017, they suddenly vanished. The carcasses stopped washing up ashore, and the sharks were no longer seen swimming in that area, causing conservation concerns for the species.

“The decline of white sharks was so dramatic, so fast, so unheard of that lots of theories began to circulate," Michelle Jewell, an ecologist from the Michigan State University Museum, told Hakai Magazine.

Some of the theories were that the sharks had just died off from being constantly persecuted by these killer whales.

However, a new study published in the journal Ecological Indicators found that the sharks didn’t just die off; they simply migrated and found refuge in a different area.

According to the report, scientists tracked human-shark incidents and found that South African shark populations had moved from the Western to the Eastern Cape, such as to Algoa Bay and the KwaZulu-Natal coast.

“The number of predation events by killer whales is likely more frequent than documented, as not all white shark carcasses would have washed ashore and been recorded,” the study read, adding that the fear of being hunted significantly affected how the sharks behaved, and the incidents led to white sharks quickly abandoning the area.

The study also found no evidence of a species decline in South Africa but notes that ongoing monitoring of their locations is essential. 

Despite protective measures put in place in 1991, the study states there's a decrease in the average size of female white sharks in bather protection programs, and there's been no population increase.