Monterey >> An unusually large amount of orcas have been gathering in Monterey Bay over the past eight days to gang up and kill gray whale calves at a frequency a local biologist calls “unprecedented.”
Starting April 20, orcas have been reportedly sighted killing four calves in seven days.
“It’s been pretty exciting lately, we’ve seen the killer whales here for eight days in a row,” said Nancy Black, a marine biologist and co-owner of Monterey Bay Whale Watch. “The first attack was pretty spectacular because there was 33 killer whales involved in that, which is an extraordinary number.”
Black, who’s been studying orcas and other marine life in the area for nearly 30 years, said typically there are groups of five to 12 killer whales in a gray whale attack.
Shawn Johnson, the director of veterinary science at the Marine Mammal Center, said he hadn’t heard about the killings.
“It’s not uncommon for orcas to prey on gray whale calves,” he said, adding he didn’t have any other information on how frequently these attacks occur.
The first attack took place later than usual, possibly because the gray whale migration went a little farther south than normal off the coast of Mexico, delaying their arrival in Monterey Bay. Ever since the gray whales arrived, the orcas have parked out around the bay.
“Usually the killer whales come in and out, they aren’t here every single day,” Black said. “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.”
Nine killer whales Black calls Emma’s group were involved in all four killings.
“It’s her mother, (Emma) her daughter, and her granddaughter, plus another couple of her offspring,” Black said. “So it’s a whole family, because killer whales do live in family groups.”
Black says other pods of orcas from different areas wouldn’t know how to hunt a gray whale, explaining Emma learned from her mother.
“They learn different methods of hunting from different areas so it’s passed on through the generations,” she said. “And this particular group, Emma’s group, is very good at it.”
Like elephants, the orcas live in matriarchal societies.
“The females are in charge and even the males will stay with their mothers their entire lives,” Black said. “While with most animals they leave, with killer whales they’re like mama’s boys.”
Black believes part of the reason for the killings could be to teach their young how to hunt, because there are several juveniles in the group. She said one of the youngest ones, named Little B, is less than 6 months old but is already learning how to hunt and eating some of the gray whales.
“They learn early because it’s pretty dangerous for the killer whales to hunt a gray whale because the mother gray whale can slam them with their fluke,” she said.
The orcas share their prey with the rest of the group, even with those that don’t take part in the hunting, like Emma’s mother. Black said orcas do binge feed and they could be killing at such a high frequency because they can eat a lot at once instead of catching a ton of seals and sea lions.
“One gray whale provides a lot of food for the whole family for two days,” she said.
Another remarkable part of the killings is the speed in which the orcas are capturing their prey.
“On Wednesday, they caught a gray whale in record time, in like 20 minutes,” Black said. “Usually it takes on average one to two hours for killer whales to actually separate a gray whale calf from its mother and drown the calf.”
Black said it’s unclear how the orcas know how to be at the right place at the right time to hunt the gray whales.
“It’s still a mystery, but they are very intelligent,” she said.
While it’s unknown if the orca attacks will continue, Black said she thinks it could keep up.
“The time for the gray whale mothers and calves is April and May, so it definitely could,” she said. “Usually there will still be killer whales here through that period and this looks like so far a good number of gray whale mothers and calves coming through.”
Tommy Wright can be reached at 831-726-4375.
