In unprecedented footage, orcas have been filmed ramming one of the world’s heaviest fish so hard that it explodes. It’s thought that the bizarre behaviour could be a type of feeding strategy - or alternatively, maybe orcas just like blowing things up.
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Under the heat of the midday sun, a pod of orcas loitered in the sun-drenched waters off the coast of Baja California Sur, Mexico. Then researchers witnessed something incredible.
The pod had recently killed an enormous sharp-tail sunfish. Now an adult female held the carcass in her mouth by its tail fin. Without warning, an adult male accelerated towards the scene, belly-up, and as the female released the fish, the male torpedoed into it. The sunfish exploded into smithereens.
The behaviour, reported in Frontiers in Ethology, had never been witnessed before, but less than a year later, it was seen again. A second, identical event was recorded around 100 miles away, in the Gulf of California.
Researchers aren’t sure what to make of it. Orcas are smart, social apex predators. They hunt in coordinated family groups called pods, where they use a variety of techniques to bring down their prey. This can include strategic drowning, deliberate beaching and wave-washing, where pods create waves to knock seals off ice floes.
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In the Gulf of California, sunfish, which can grow over 3m long and weigh up to 2,000kg, are often targeted by orcas. In both of the encounters, the sunfish were already dead, and after they were blown apart, other pod members moved in to eat the leftovers.
Researchers point out that this could be a form of “parental investment.” By exploding the sunfish, the adults created hundreds of bite-sized pieces for younger pod members. Sharp-tail sunfish also have an outer, gelatinous layer that harbours distinct microbial communities. When fragments of this tissue shear off and are consumed by the orcas, bacteria may be transferred and could provide nutritional or functional benefits.
However, this doesn’t mean the interaction could not have served other purposes too. “We think this may help younger orcas feed more easily, or it could also just be for fun,” says Kathryn Ayres from the University of Sheffield. “Orcas are known for playing with their food.” In other words, the adults may have performed the stunt for entertainment.
Read more about the study.
Image and video credit: Kathryn Ayres
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