How are orcas able to hunt dolphins and porpoises?
Highly social, intelligent orcas or ‘wolves of the sea’ hunt large prey in pods. While only one species, orcas occur in two adaptations: nomadic marine mammal hunters and more stationary fish-eaters.
Similar to the way they pursue seals, orcas can breach and knock smaller, toothed whales out of the water to confuse and tire or stun them. And the pods often split up in order to hunt individuals. They will share a kill with their kin, rewarding co-operation.
It is possible for a chase to go on for some time. In Prince William Sound in the Gulf of Alaska, high-speed surface pursuits of Dall’s porpoises, which involve orca aerial leaps, have lasted for up to 43 minutes.
Few people ever witness orcas attacking porpoises and dolphins. However, in 2016, a cruise skipper in Monterey Bay, California, filmed eight to ten that had convened to chase grey whale calves but instead ambushed a 1,000-strong common dolphin ‘super-pod’. Anticipating the dolphins’ course, the orcas lay low, hiding under the surface before charging upward to hit their quarry.
Some orcas specialise in hunting other cetaceans, and work as a pod to kill their quarry.