When a whale washes ashore, it’s often in a sorry state — bloated, decomposing, stinking to high heavens.
But the 52-foot fin whale that stranded itself on San Diego’s popular Mission Beach on Dec. 10 looked big and blubbery, just as a whale should. Kerri Danil had no idea why this seemingly healthy giant had flung itself onto the beach.
“We were surprised,” said Danil, a National Marine Fisheries Service research biologist called in to examine the whale. “The animal appeared healthy based on its body condition and how robust it was.”
But her team would soon unravel the mystery. The likely culprit: killer whales.
The beached fin whale seems to be the latest victim of a pod of marauding orcas that has been eating and harassing dolphins and other marine mammals along the coast of Southern California. Whale watchers have spotted the group on at least 10 days between Dec. 11 and Christmas, according to the nonprofit California Killer Whale Project.
For marine biologists in California, the arrival of this group of about a dozen killer whales, normally found along the coast of Mexico, doesn’t represent any sort of menace. It’s instead a sign of a recovering ecosystem off the Southern California coast, one in which marine mammals have increased enough to sustain hungry orcas.
“We are seeing marine mammal populations rebounding, and it’s not too surprising that their predators are rebounding too,” said Robert Pitman, a marine ecologist at Oregon State University’s Marine Mammal Institute.
The likely ambush on the fin whale, an animal many times an orca’s size, illustrates the predators’ amazing hunting prowess. Only last year did scientists report how a pack of killer whales ganged up to kill a blue whale. And a recent spate of orcas striking and, in some cases, sinking boats around the Strait of Gibraltar has put European yachters on edge.
“Killer whales are the closest thing to a T. rex we have on this planet now,” Pitman said.
A whale whodunitMission Beach, north of downtown San Diego, is your quintessential Southern California strand, often packed with surfers and sunbathers. Dead leviathans are rarely part of the mix.
When Danil and three colleagues arrived on the scene, they first looked for signs of the usual suspects behind the death of a fin whale: a strike by a ship or entanglement in fishing gear.
Seeing no evidence that a boat or rope did the marine mammal in, Danil’s team sampled tissue from a strange set of bite marks on and around the animal’s fins. They determined the whale was wounded while alive since the animal had not expired when it washed ashore.
The gaps between the parallel “rake marks” made by the predators’ teeth were too big to have been made by a shark or a dolphin. They sent the photos to others including Pitman, who had studied orca attacks on fin whales off Baja California in Mexico. He quickly concluded that killer whales were the culprits again.
Here is what likely happened:
The pod of orcas pounced on the fin whale, grabbing onto its fins in a team effort to drown or exhaust its massive prey. Attempting to flee, the fin whale hurled itself ashore and died.
“It figured it would take its chances on the beach rather than with these killer whales,” Pitman said. Adding to the evidence of an orca assault is that, the next day, someone spotted killer whales swimming north away from the scene.
There has been an uptick in killer whale sightings in Southern California since 2014, according to Alisa Schulman-Janiger, co-founder and lead research biologist of the California Killer Whale Project.
Decreasing water pollution, along with protections against hunting and harassing both mammal-eating killer whales and their prey under the Marine Mammal Protection Act of 1972, has allowed orcas to return to Southern California. Rising temperatures, too, are pushing more species north.
“A lot of species and populations of animals that typically weren’t in Southern California waters are starting to move in,” Pitman said.
