Great white sharks are menacing, daunting apex predators, and we usually associate it with the top of the food chain of marine life. But little did we know that these silent hunters are actually not the ocean’s top predators. A new study reveals that the title belongs to the black and white orcas or killer whales, and sharks are scared of them.
This study comes from a paper in Nature Scientific Reports by senior research scientist Salvador Jorgensen at the Monterey Bay Aquarium and his colleagues. While studying great white sharks, Jorgensen and his team noticed that when orcas come to the neighborhood, the sharks get away from it, and in many cases did not return for months. It’s like a bully scene from a movie.
In 2009, the team radio-tagged 17 sharks around Southeast Farallon Island in Greater Farallones National Marine Sanctuary. The sharks were just minding their business, eating a young elephant seals in the waters around the island, which they regularly do between September and December. But when a pod of orcas entered the waters for just a couple of hours, the sharks swam away from there and most didn’t return that season.
Jorgensen wasn’t sure whether this situation was just a one time thing or common. Therefore, he and his team looked deeper in the data, examining information about 165 great white sharks tagged in the Farallones between 2006 and 2013. They compared that with whale, shark and seal surveys collected in the marine sanctuary collected over 27 years.
“The research in this paper combines two really robust data sources,” said Jim Tietz, co-author of the study and Farallon Program Biologist at Point Blue Conservation Science. “By supplementing the Aquarium’s new shark tagging data with Point Blue’s long-term monitoring of wildlife at the Farallon Islands National Wildlife Refuge, we were able to conclusively show how white sharks clear out of the area when the orcas show up.”
Apparently, the whole orcas-are-coming-let’s-get-outta-here was a standard pattern. When orca whales entered the area, the sharks bolted from Southeast Farallon and nearby islands. “When confronted by orcas, white sharks will immediately vacate their preferred hunting ground and will not return for up to a year, even though the orcas are only passing through,” said Jorgensen.
A report said that if orcas get within two miles of the islands, sharks will eave. In an average year, researchers were able to document 40 elephant seals eaten by sharks. But in years where the orcas make an appearance at around 2009, 2011 and 2013, that number drops by 62 percent from the previous year.
It’s a good situation for the seals if the orcas don’t eat them in turn. Imagine having to live in fear for the longest time of your life and then this species is making your life better. You can hunt for fish and do other stuff freely, I’d be a happy seal for sure. It’s still unknown, though, whether the orcas are simply bullying the competition out of the way so they can get on the calorie-rich elephant seals or they’re targeting the sharks as their next preferred meal.
“On average we document around 40 elephant seal predation events by white sharks at Southeast Farallon Island each season,” said Scot Anderson. “After orcas show up, we don’t see a single shark and there are no more kills.”
Why so afraid?
Sharks can grow up to 6 meters long, and they’ve got saw-like teeth which can tear apart any flesh effortlessly. So why are they afraid of orcas? Well, to begin with, not all of us know that white shark/orca encounters doesn’t end well for the sharks. There was a recorded interaction in 1997 when fishermen near Southeast Farallon witnessed a pair of orcas kill a young great white that tried to nose in on the sea lion they were eating. The orcas bashed him to death then ate his liver. Welp, if I were a shark who was around that scene, I would be scarred for life and not want to get near orcas ever again.
Orcas, interestingly, seem to really like shark liver so much. In 2017, there were five corpses of great white sharks on the beaches of South Africa, and their livers were absent. It was the work of orcas, which killed the sharks, ate the livers only, and left the rest of the corpse. “It’s like squeezing toothpaste,” said Jorgensen.
When we don’t know about this new fact, we surely have a hard time picturing great white sharks, one of the larger species of shark in our oceans, to be afraid of a bigger version of dolphins. However, it turns out that they are and fear as well as risk aversion seem to be shaping where and when these animals hunt, which in turn influences the oceanic ecosystems they inhabit.
From this findings, researchers are beginning to understand how the instinct to avoid predators can have impacts on all kinds of ecosystems including the oceans. “We don’t typically think about how fear and risk aversion might play a role in shaping where large predators hunt and how that influences ocean ecosystems,” said Jorgensen. “It turns out these risk effects are very strong even for large predators like white sharks—strong enough to redirect their hunting activity to less preferred but safer areas.”
Well isn’t this a surprising one. I’d never known that these majestic great white sharks cower when there are orcas around and I’d never known what the orcas can do to these sharks. What about you? Did you know about this before? What do you think? Tell us your thoughts in the comments below.