Great White Sharks Leave En Masse When Orcas Are Around

Great White Sharks Leave En Masse When Orcas Are Around

The great white shark (Carcharodon carcharias) is the most fearsome ocean going predator to man, but when killer whales (Orcinus orca) are around, they flee en masse, according to a study by researchers with the Monterey Bay Aquarium. The study, which tracked 165 great white sharks between 2006 and 2013, and observations around the Southeast Farallon islands since 1987, a known seal rookery, noted that all great white sharks in the vicinity of the Farallons would leave en masse when killer whales were around the islands, even if the orcas were just passing through.

“What we saw was that when orcas came close to the island during shark season, all of the sharks would take off,” Salvador Jorgensen, a Monterey Bay Aquarium researcher and lead author of the study told the San Francisco Chronicle. “As a predator that has been successful for millions of years, that may be the card white sharks know how to play that has kept them alive so long — knowing when to fold.”

The researchers noted that the fear the great whites have of the killer whales is so strong that the sharks don’t return to the islands for the rest of the feeding season, and sometimes would stay away from the islands that provide rich, fat seal prey for as long as a year.

And there is certainly a reason for great whites to fear the largest member of the dolphin family. They are prey for killer whales. In 1997 off the Farallon Islands, a group of whale watchers witnessed a killer whale attack and kill a great white shark, feeding on the liver of the dead shark. In 2000, a similar event caused 100 great white sharks to leave the area. One tagged great white shark dove down to a depth of 500 meters and swam to Hawaii.

Great white sharks can grow up to 20 feet in length and weigh 7,000 pounds, while killer whales grow between 22 and 26 feet and weigh 12,000 pounds. It is not known how the sharks can detect the presence of killer whales in the vicinity, but the researchers have their theories.

“My gut feeling, and this is the topic of future work, is that the sharks are able to detect the orcas using their sense of smell,” Jorgensen said. “The smell that orcas have swimming around in the water is probably something that every shark can sense.”

The complete paper, “Killer whales redistribute white shark foraging pressure on seals” can be read in its entirety on the Scientific Reports website.