While being caught in the jaws of a killer whale may be terrifying, it’s not always a death sentence. Killer whales, also known as orcas, occasionally conduct coordinated attacks on animals they have no intention of eating—including sea turtles.
In the winter of 2017, photographer and biology student Nicolás Dávalos was conducting fieldwork off the coast of Isla Isabela, the largest of the Galapagos islands. Dávalos, snorkelling at the surface, watched in awe as a group of three orcas—an adult and two juveniles—went after a pair of green sea turtles.
The eldest orca began using the front of its head, known as the rostrum, to violently spin a turtle. Meanwhile, one of the juveniles grabbed a second turtle by the fin and dragged it below the surface. The orcas toyed with these creatures for half an hour before abruptly swimming off, leaving the turtles uneaten; at least one of them seemed to have survived, Dávalos adds.
“Killer whales will at times play with potential prey for a half hour or more, and then just move on, leaving the victim unharmed”, says Robert Pitman, marine ecologist at the National Oceanic and Atmospheric Administration’s Southwest Fisheries Science Center.
“Other times they will chase prey around and kill it but not eat it. They’re like cats in that way—can’t resist the urge I guess”.
Orcas around the world regularly engage in this type of behaviour. In the Pacific Northwest young orcas frequently harass and kill harbour porpoises, but rarely eat them, says Michael Weiss, a field biologist and doctoral student with the Center for Whale Research.
An orca helps herd a school of herring in the deep waters of the Andfjorden in Norway.
PHOTOGRAPH BY PAUL NICKLEN, NATIONAL GEOGRAPHIC CREATIVE
The behaviour may appear gratuitous on the surface, but Weiss believes it serves an important function for the orcas. “It could be some kind of training or it could just be a kind of play”, says Weiss.
“If you're a hunter, keeping a potential prey item alive for a long period of time—continually chasing down and catching it—is a good way to practice a lot of the skills that you might need later in life”, says Weiss, who notes that this behaviour is most often demonstrated by young orcas.
Orcas are well equipped to make a meal out of an unsuspecting turtle. Armed with a set of powerful jaws and tough teeth, which can be four inches long, orcas can easily break through a sea turtle’s solid shell.
Only orcas, crocodiles, jaguars, and a few species of large shark have the strength to penetrate the durable shell of an adult sea turtle. And because sea turtles have no defenses aside from a thick shell, even an adult sea turtle is low hanging fruit for these predators.
“Because of their massive size and strength [orcas] can crush the flesh and hard tissues of their prey and then swallow it with no problem”, says Jaime Bolaños-Jiménez, a PhD candidate at the Institute of Marine Sciences and Fisheries at Veracruz University in Mexico.
“Hard-shelled turtles have been found in the stomach contents of some stranded orcas, so I think they have no problem consuming them”, says Bolaños-Jiménez.
Although this behaviour has been witnessed before, it’s quite rare. Sea turtles are not a typical prey item for orcas, but the ability to hunt sea turtles may be becoming increasingly useful to orcas, photographer Dávalos notes. “They may have developed a taste for marine reptiles in the Galapagos because there are now so many”.
Thanks to legal protections and captive breeding, the number of green sea turtles in certain parts of the Galapagos has increased, says Dávalos. But globally, green sea turtles are endangered and their numbers are declining rapidly thanks to a myriad of human-induced factors including illegal poaching, habitat loss, and marine pollution. (Read: “Why Life Is So Tough for Sea Turtles”).
Orcas employ a wide variety of hunting techniques to catch their prey. These techniques are difficult to master and can only be acquired through the teachings of an elder.
The way orcas pass down their knowledge is far more sophisticated than “monkey see, monkey do”. Orcas are one of a small number of species known to expend significant time and energy on the instruction of their young. (Read: “These Animal Babies Grow Up Without Any Help From Parents.”)
Once thought to be a trait unique to humans, this type of teaching has been observed in a small but diverse group of species including cheetahs, meerkats, and bottlenose dolphins.
Scientists don’t know for sure whether orcas antagonise other animals to hone their hunting skills or to have a good time, but videos like these may help solve the mystery.
“Orcas are highly flexible in their behaviour”, Bolaños-Jiménez says. “They are curious, joyful, and intelligent and so they can display many types of behaviours. The valuable thing here is that a diver had the chance to document the behaviour for science”.