They are known as the world’s largest predatory fish in the world, formidable hunters that have nothing to fear: white sharks. Almost nothing, because there is one other species (besides humans) that is trying to kill them. Adult white sharks have been known for some time en masse fleeing from killer whales – which are known for good reason killer whales. And some orca groups even appear to specifically target young white sharks, write Mexican and American biologists in now Frontiers in Marine Science.
Orcas hunt in groups: for example, there are famous images of toothed whales that collectively produce a ‘air bubble curtain’ under water with which they circle a school of fish. Different groups can specialize in different prey and develop their own techniques. This also appears to apply to the orcas now being studied in the Gulf of California. The researchers filmed from the air on two separate occasions how a total of three young white sharks were killed, although it is not entirely clear whether the same orcas were involved in both cases.
Involuntary motionlessness
The orcas first turned the sharks onto their backs at the water surface so that they could no longer move and entered a state of tonic immobility: involuntary inertia due to complete muscle contraction. For many animals, freezing is a last resort – predation can sometimes be avoided by pretending they are already dead. But the orcas used the fossilization to their advantage: an upside-down shark is so disoriented that it cannot escape and cannot bite. They then pushed their prey underwater. There they cut out the liver and divided it among themselves. The rest of the carcass was discarded.
It is no coincidence that orcas go for the liver: it is extremely energy-rich. For that reason, it seems more logical to go for an adult white shark. After all, with a length of up to 6.5 meters, it also has a larger liver and is also a more formidable competitor when hunting other prey. Previous observations mainly revealed attacks on adult sharks. But the advantage of hunting younger sharks, with a length of ‘only’ 2 meters, is that they are less experienced and have not yet learned to fear orcas.
It was striking that both attacks took place in August, although not in the same year. Possibly, the biologists speculate, shark hunting is a seasonal phenomenon, although confrontations between orcas and white sharks may become more frequent. Due to marine heat waves and a more frequent occurrence of the El Niño effect, young white sharks are moving further and further north.
A killer whale attacks a white shark in the belly.
Marco Villegas
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