Extraordinary underwater videos have captured orcas making sunfish explode by ramming them at high speed. The behaviour may help juvenile orcas feed by breaking the prey into many small pieces, but it also appears that the orcas may enjoy playing with their food.
鈥淚t鈥檚 a hunting tactic, but that involves a play game in the process,鈥� says , an independent marine biologist in Mexico. 鈥淭here鈥檚 鈥榟igh-octane鈥� adrenaline and a lot of other hormones rushing through their bodies, so, of course, there鈥檚 got to be some sort of excitement.鈥�
Sharp-tail sunfish (Masturus lanceolatus) are among the largest bony fish, weighing up to 2000 kilograms. Higuera had already seen groups of orcas (Orcinus orca) attacking sunfish in the Gulf of California, ripping off parts of their flesh and tossing them around to each other in a playful manner. In the past few years, he had even witnessed them .
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Then, in July 2024, his colleague at US non-profit organisation Beneath the Waves caught an explosive interaction on her GoPro camera while diving in the Gulf of California. An adult female orca held onto a dead sunfish while an adult male orca swam upside down towards it at full speed. The female released the sunfish at the last second, and the male hit it with so much force that the fish burst into a flurry of small fragments.
A year later, tourist Hector Franz shot a similar underwater scene in the same bay. This time, an adult female rammed right-side-up into a sharp-tail sunfish held in place by another adult female, popping it into pieces. Combined, the two events mark the first time scientists have seen such behaviour by orcas, say Higuera, Ayres and their colleagues.
Sunfish have 鈥渁n incredibly dense, rubbery, collagenous鈥� outer layer that鈥檚 harder to bite through, so bursting them open could be an effective way to feed on them, says Higuera.
鈥淭he explosive fragmentation seemed mostly to be of the stiff gelatinous capsule that makes up a high percentage 鈥� more than 80 per cent in large fish 鈥� of the body mass of the sunfish,鈥� says at University College Cork in Ireland. 鈥淚 suspect that calves cannot achieve enough force to do this, as their mass is too low. But they can exploit a cloud of objects that contain tasty morsels.鈥�
Earlier sightings without full footage indicated that the entire pod was involved in a strategic attack process leading up to the rammings, says Higuera. The findings point to advanced cooperative hunting skills and even planning 鈥� especially adapting their techniques for different kinds of prey, he says.
Higuera suspects that popping the sunfish offered a learning experience for the calves, while providing them with bite-sized snacks. Simultaneously, these events could also reinforce social bonds through 鈥減lay鈥� and social learning in this highly intelligent species, he adds.
at the University of Tennessee in Knoxville says it is possible the orcas were having some fun in demolishing the fish, but play wouldn鈥檛 be the only goal, as there is clearly cooperative foraging going on as well.
鈥淥ne of the fascinating things about play is that it can be a driver of behavioural innovation,鈥� says at the University of Pisa, Italy. 鈥淚t鈥檚 possible that a behaviour like this may have originated in a playful context and later acquired a feeding function, or vice versa. At this stage, we simply don鈥檛 know.鈥�
Frontiers in Ethology
