Video from excited ecotourists shows how orcas manage an unlikely feat of predation: killing a massive whale shark. And that’s just one of the killer whales’ conquests.
Four videos of orca hunting sprees, the earliest from 2018 and the latest from 2024, suggest that an orca pod in the Gulf of California is specializing in hunting sharks and their relatives, researchers say. Other targets include such ecotourist faves as mobula rays, says marine biologist Francesca Pancaldi of the marine science center in La Paz associated with Mexico’s Instituto Politécnico Nacional. She and her colleagues lay out their ideas for orca specialization November 29 in Frontiers in Marine Science.
Orcas rank as a top — and extremely versatile — predator in the world’s oceans. Orcinus orca pods have been documented taking down adult great blue whales off the Western Australia coast, and harassing boaters off Europe’s Iberian coast (SN: 2/3/22) They’ll prey on sea turtles, cephalopods and seabirds. Some orcas will “karate chop” a thresher shark. Others beach themselves on sandy shores to pick off vulnerable pinnipeds.
How orcas feed in the eastern tropical Pacific Ocean has barely begun to be studied, says coauthor Erick Higuera Rivas, a marine biologist at Conexiones Terramar in La Paz. The whale sharks (Rhincodon typus) that orcas target are the largest fish in the world. Adults can grow to 18 meters in length, and possibly more (longer than a school bus). Whale sharks would be summer-movie extravagances of terror if only they had biting teeth. As filter feeders, they just glean the weak background-soup of ocean life.
Orcas’ physiology should hamper their ability to catch whale sharks. “They have lungs,” says Pancaldi. The whale shark, with gills, can do infinite lurks and dive 2,000 meters deep, while its mammal predator has to break off the chase, swim up to the surface and breathe.
To eat shark, orcas have to keep the shark from diving, and it takes a pod, Pancaldi says. Orcas hound the sharks, and even the young and the small may join in, snapping or blocking escape routes. Flipping the shark over or otherwise jolting it into the scared-rabbit freeze of tonic immobility is a big success. Biting off the pelvic fins and claspers from the lower body doom the shark to bleed out. Then the orcas can feast on what they really want, the shark liver, huge and full of fat. The rest is trash.
All four doomed sharks in the videos were young and small — merely five to six meters long. Three of the four videos show the same orca, a distinctive male, which the researchers nicknamed Moctezuma. But, the researchers say, it’s the grandmothers, especially the matriarch of the pod, who transmits cultural knowledge, such as the technique for getting yummy shark livers.