June 29, 2017
Orcas Of Monterey Bay On 'Killing Spree': What's Making These Killer Whales So Vicious Against Gray Whales?

Orcas in Monterey Bay in California are reportedly on a never-before-seen "killing spree," with killer whales in the area feeding on gray whale calves at unusually high rates.

Earlier this week, a dramatic video showed nine of these Monterey Bay killer whales circling a mother gray whale and her calf, attacking their prey with hitherto-unseen ferocity. According to the Daily Mail, orcas are smart enough to memorize the migratory habits of gray whales and usually take quite a while to successfully hunt down their prey. However, in this case, the pack mentioned above had feasted four times in the eight days as of Friday, a surprisingly high figure for the already-fierce orcas.

According to Monterey Bay Whale Watch marine biologist Nancy Black, that family of nine killer whales was involved in all four of the attacks, but the first attack had involved a whopping 33 orcas.

"Usually the killer whales come in and out. They aren't here every single day," Black told the Monterey Herald in an interview.
"We see them more often in April than May by far, but they just seem to be hanging around and waiting for more gray whales to come through."
Marine Mammal Center (California) director of veterinary science Shawn Johnson was quoted by the Associated Press (via the Washington Post) as saying orcas feeding on gray whale calves is nothing unusual. He wasn't aware of the "killing spree" involving the orcas at Monterey Bay, and didn't explain why these creatures hunt as aggressively as they do. But Black offered an interesting theory in the AP report -- the recent killings may be a case of adult killer whales teaching younger ones how to hunt.
"(Killer whales) learn different methods of hunting from different areas so it's passed on through the generations. And this particular group... is very good at it."
The Associated Press wrote that the orca pod in question is a nine-whale group called "Emma's Group," named after an adult female whale who serves as the most prominent member. Also included in the pod are Emma's mother, her daughter, and some other young orcas, including one (nicknamed "Little B") who is less than half-a-year old. According to Black, juveniles of the species learn to hunt while young because of the dangers involved when hunting down gray whales.
"The mother gray whale can slam them with their fluke."
Although it's part of an orca's tendency to hunt peace-loving prey like gray whales, the Monterey Bay killings underscore the fact that the latter animal's numbers have greatly been reduced through the years. The World Wildlife Foundation's fact sheet on gray whales states that the animals number about 26,000, though there are only about 150 western gray whales, making this particular species critically endangered. The more common Eastern North Pacific variety was previously listed as an endangered species, but removed from the list in 1994 after recovering from "very low levels."

Scientists are also concerned that the orcas of Monterey Bay are attacking much faster than they usually do – an attack that had taken place on Wednesday only took 20 minutes to pull off, as opposed to the hours it normally takes for killer whales to isolate a baby gray whale from its mother.

If there's something to look for following this unprecedented series of orca attacks, it's that the Monterey Bay group may likely become "more social" in the days to come. Black told the San Francisco Gate that it's normal for killer whales to do this once they've finished feasting on their prey, but at the moment, they don't appear to be anywhere close to being full.

[Featured Image by NOAA Fisheries and Vancouver Aquarium/AP Images]