The last week has seen a pod of orcas go on something of a killing spree. A pod of nine orcas in Monterey Bay, off California, have seemingly perfected the technique of killing gray whales as they migrate up the eastern coast, with one failed attempt even caught on camera in amazing footage from a drone.
Over eight days the orca successfully killed four calves, something that marine biologist Nancy Black from Monterey Bay Whale Watch says she has never seen in the 30 years she has been observing the whales. In one attack, 33 orcas joined up to drown and then devour a calf, while in another, the core pod of nine whales took just 20 minutes to kill an infant whale, much faster than the hours it usually takes.
Every year, gray whales migrate up and down the east coast of North America in what is thought to be the longest known migration of any mammal. The leviathans spend much of the summer months feeding in the Bering Strait off the coast of Alaska. When the ice starts to form, they start their 20,000-kilometer (12,500-mile) migration south, to the breeding grounds in the warm waters off the Baja California Peninsula.
Here, the whales mate and the females give birth. They then have to steel themselves for a treacherous swim back to Alaska. The exhausted female whales, which have not fed since the previous season, now have to return with infant in tow, and the orcas know this. They wait at strategic locations along the coastline, Monterey Bay being one such place, for the migration to begin.
This year, however, the migration has been late to start. It’s because of this, Black suggested, that the orcas may have been getting anxious or impatient as they have been waiting for the mothers and their calves to pass through Monterey Bay. This could help explain why this particular pod of orcas suddenly started this spate of quick killings.
Hunting gray whales is a risky and dangerous business. The mothers will fight viciously to protect their calves, trying to keep the infant on their backs, up and out of harm's way, while at the same time swinging their tail to try and hit the orcas. The orcas, in turn, try and distract the mothers by working in a pack to nip and bite her, while others in the pod work on separating the calf from the mother. If this is achieved, the odds are not good for the infant as the orcas hold them down to drown them.
While the risks are great, the rewards are massive for the orcas, with a gray whale calf providing plenty of food, which orca pods share with every member, regardless of whether they helped in the hunt or not.