Sharks are widely considered to be the most feared apex predators in the ocean, but they usually hunt creatures smaller than them: fish, seals, penguins, etc. Whales are usually safe from sharks due to their sheer size. But now not even the largest creatures on Earth can consider themselves safe.

A humpback whale calf off the coast of South Africa was recently witnessed being hunted and likely eaten by a swarm of 10 to 20 dusky sharks. It was the first documented case of a shark attacking a whale, reports New Scientist.

The hunt appeared slow and methodical, taking place over the course of several hours. The whale calf could be seen thrashing vigorously at the surface whenever it was bitten, desperately attempting to swim away or shake the sharks off. Eventually it succumbed to exhaustion, drowned and was likely eaten. The calf's mother was nowhere to be seen, so it's unclear how the calf came to be swimming alone in the first place. The presence of the mother likely would have warded off the sharks.

Even though the whale was a calf, it was roughly 4 meters long, still significantly larger than the 2- to 3-meter dusky sharks. This was not a kill the sharks likely could have made alone, raising the question of whether it was a coordinated attack — planning behavior which is not typically associated with fish.

Matt Dicken of the KwaZulu-Natal Sharks Board in South Africa, whose team witnessed the incident, noted that while cooperation is not unheard of among sharks, this attack was most likely opportunistic rather than organized. The sharks aggregated around the vulnerable calf and eventually a feeding frenzy occurred.

Although this is the first time such an attack has been documented, Dicken thinks these kinds of attacks likely happen more often than previously believed. “It’s still probably quite rare, but they are happening,” he said.

Since the East African humpback whale population is growing, this kind of behavior could become more common over time, though the conditions that led to this attack may have been unique, too. After all, the calf was without its mother, and it may have been injured or weakened by whatever ordeal resulted in its abandonment.