An unusually large number of orcas have been spotted in Monterey Bay over the past eight days, killing gray whale calves at an “unprecedented” rate. Beginning on April 20, orcas have been seen killing four calves in seven days.

According to Nancy Black, a marine biologist and co-owner of Monterey Bay Whale Watch, the first attack was “pretty spectacular” as it involved 33 killer whales, which is an extraordinary number.

Beginning on April 20, orcas have been seen killing four calves in seven days. Image credit: National Geographic
Beginning on April 20, orcas have been seen killing four calves in seven days. Image credit: National Geographic

Black has been studying orcas for nearly 30 years and said that usually there are groups of five to 12 orcas in a gray whale attack.

Killer whales have killed four gray whale calves in eight days

The first attack took place later than usual, as the gray whale migration went a little further south than normal off the coast of Mexico, which delayed their arrival in Monterey Bay. Upon their arrival to Monterey Bay, the killer whales have been preying on the gray whales.

“Usually the killer whales come in and out, they aren’t here every single day,” said Black, according to The Mercury News. “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.”

Black says that a group involving nine orcas, which she named Emma’s group, is responsible for all four killings. She claims that the mother (Emma), her daughter, her granddaughter, and several other offspring conform the family that has killed four gray whale calves in the last couple of days.

She said that other pods of orcas from different areas would not know how to hunt a gray whale, and she explained that Emma must have learned it from her mother.

“They learn different methods of hunting from different areas so it’s passed on through the generations,” said Black. “And this particular group, Emma’s group, is very good at it.”

Image credit: National Geographic
Image credit: National Geographic

Killer whale group is very fast and efficient

Orcas live in matriarchal societies, just like elephants. Black noted that the females are in charge of the groups, and even the males will stay alongside their mothers their entire life. She believes that part of the reason for the killing spree could be to teach their young how to hunt, as there are several juveniles in the group. One of the youngest, named Little B is not yet six months old but is already learning how to hunt and eats some of the gray whales.

Black explained that the orcas learn early because it is dangerous for them to hunt a gray whale because the mother gray whale can slam them with their fluke. After the killing is over, the killer whales share their prey with the rest of the group, even with those who do not take part in the hunting.

According to Black, orcas binge feed and they could also be killing at a high frequency because they can eat a lot at once instead of catching several seals and sea lions. A gray whale can provide food for two days for an entire orca family. She noted that a remarkable part of the Monterey Bay killings is the speed in which the whales are capturing their prey.

She recalled that on Wednesday, the orcas caught a gray whale in 20 minutes, a record time. Usually, the killer whales spend between one or two hours to just separate a gray whale calf from its mother and drown it then. The attacks could stretch through May, as gray whales will stay in the area. For Black, it is unclear how the orcas know how to be at the right time and place to hunt down the gray whale calves.

“It’s still a mystery, but they are very intelligent,” said Black.

Source: The Mercury News