Great white sharks and killer whales are the two most deadly predators in our oceans. But what happens when these killers cross paths and who comes out on top?
Great white sharks, Carcharodon carcharias, and killer whales, Orcinus orca, are quite possibly the top two when it comes to the most dangerous animals in the sea. Both are extremely fast, ruthlessly efficient and feared across the world. The question of who would win in a fight has until now been a largely hypothetical conundrum. But a new study by researchers in America may just finally settle the debate once and for all. Whilst researching how sharks and seals interact near a small island off the Californian coast, the arrival of a pod of orcas gave scientists a fascinating insight into how these two titans interact with each other. But who comes out on top and why?
An actual fight between great whites and orcas, although potentially very impressive and spectacular, is actually very rare in nature. They very rarely overlap enough to cause conflict, but when they do who is the first to swim away? When studying great white shark feeding behaviour, at Southeast Farallon Island in California, Salvador Jorgenson and his team from Monterey Bay Aquarium were lucky enough to find out. Their work involves electronically tagging sharks and looking at how their spatial movement varies as they hunt elephant seals in the area. In this particular study, published in nature, the white sharks seemed happy enough hunting down seals until a pod of killer whales showed up out of the blue. In a surprising twist it was in fact the sharks who vacated the area whilst their rivals passed through. Within eight hours all the sharks in the area had left and even more surprisingly none of the individuals returned until the next hunting season the following year.
The team then observed the exact same outcome the following three seasons and when they looked at other shark data from other studies they found a strong trend. In a press statement Jorgensen explained “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”. There is also another winner when great whites and orcas face off and that is the elephant seals. Co-author Scot Anderson says “on average we document around 40 elephant seal predation events by white sharks at Southeast Farallon Island each season” but goes on to explain “after orcas show up, we don’t see a single shark and there are no more kills”.
Why does this happen?
It has largely been assumed that great white sharks are the pinnacle of predators, not just in the ocean but on the entire planet. So why do they flee at the sight of killer whales? And why do they not return for such a long period of time? There are two leading explanations. The first is that killer whales predate upon the sharks. This may seem unlikely but there have been documented cases of orcas killing white sharks before. In 1997 two orcas were observed by boat killing a great white that had interrupted their meal. However the cetaceans do not consume the shark meat but instead rip out their liver leaving them to slowly die. Several such shark carcases without a liver have also been found washed up on the shore where the species overlap in South Africa. But it is very unlikely that killer whales hunt down sharks but instead just come out on top if they are forced to fight each other.
The second explanation is that orcas outcompete and ‘bully’ sharks into leaving the area. Unlike whales who travel in pods great whites are largely solitary animals. Therefore when the species overlap the cetaceans often greatly outnumber the sharks. As a result they will outcompete sharks by consuming more seals and intimidate them by surrounding them. This is likely enough to scare off the sharks without any blood being shed. Either way the fact that orcas come out on top is very surprising. “I think this demonstrates how food chains are not always linear” says Jorgensen “so-called lateral interactions between top predators are fairly well known on land but are much harder to document in the ocean and because it happens so infrequently, it may take us a while longer to fully understand the dynamics.”