Orcas can take down the largest animal on the planet_tio2 828
2022-08-20 03:36:49

Animals

Orcas can take down the largest animal on the planet

It’s a fight between the ocean’s top predator and the world’s largest animal

The pink flank on this blue whale calf marks where orcas stripped the flesh off. The whale died about eight minutes after this photo was taken. This event is the second of three captured on video showing that orcas hunt and kill these massive whales.

John Daw/Australian Wildlife Journeys

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By Anna Gibbs

Killer whales are skilled assassins. They hunt everything from small fish to great white sharks. They’ve even been known to attack whales. But there had long been a question about whether killer whales — also known as orcas (Orcinus orca) — could kill the world’s largest animal. Now there’s no longer any doubt. For the first time, scientists have observed a pod of orcas bring down an adult blue whale.

Let’s learn about whales and dolphins

“This is the biggest predation event on the planet,” says Robert Pitman. He is a cetacean ecologist who works at the Oregon State University Marine Mammal Institute in Newport. “We haven’t seen things like this since dinosaurs were here, and probably not even then.”

On March 21, 2019, a team of scientists in Western Australia headed out on a boat to observe orcas. Little did they realize they would see something no one had seen before. They shared their whale tale January 21 in Marine Mammal Science.

It was “a really ominous, bad-weather day,” recalls John Totterdell. He is a biologist at the Cetacean Research Centre. It’s in Esperance, Australia. When he and his group were still an hour away from their usual orca-observing site, they slowed down to remove some debris from the water. It was pouring rain, so it was hard to see the splashing at first. Then they noticed the telltale dorsal fins of killer whales.

“Within seconds, we realized they were attacking something big. Then,” says Totterdell, “we realized, oh my, it was a blue whale.”

photo of orcas attacking a blue whale
An orca (upper left) swims into a blue whale’s open jaw and feasts on its tongue. Meanwhile, two other orcas continue to attack the whale’s flank. This event was the first time scientists observed orcas kill an adult blue whale.CETREC, Project Orca

A dozen orcas were attacking an adult blue whale (Balaenoptera musculus). Their prey appeared to be between 18 and 22 meters (59 and 72 feet) long. Its flank was covered in tooth marks. Most of its dorsal fin had been bitten off. The most brutal injury was on its face. The flesh of the whale’s snout was ripped away along the top lip, exposing bone. Like a battering ram, three orcas slammed into the whale’s side. Then another orca began feeding on its tongue. The blue whale finally died about an hour after the research team arrived.

Anatomy of an attack

Orcas tend to use the same methods every time they attack a large whale. They bite the whale’s fins, tail and jaw. This may be to slow it down. They also push the whale’s head underwater to prevent it from surfacing for air. Some may push it up from below so the whale can’t dive. “These are practiced large-whale hunters,” notes Pitman, who was an author of the paper. “They know how to do this.”

Orca hunts are brutal and usually involve the whole family. Females lead the charge. Orca calves will watch closely and sometimes join the ruckus. They’re almost “like excited little puppies,” says Pitman. The orcas will even share their meal with their extended family. The research team observed about 50 orcas picnicking on the blue whale after it died.

Caught on tape for the first time, a dozen orcas relentlessly attack a blue whale as it attempts to flee. The orcas rip off strips of flesh, ram the whale’s flank and eat its tongue. These techniques are consistent with observed attacks on other large whales.

Blue whales not only are enormous but also can be fast in short bursts. This makes them hard to take down. But other than that, they don’t have many of the defenses that other whales use. Scientists have reported, for instance, that southern right whales whisper to calves to avoid catching the orcas’ attention.

The new paper also describes two other successful attacks carried out by many of the same orcas. The group killed a blue whale calf in 2019 and a juvenile blue whale in 2021. The events happened in the waters off Bremer Bay in Western Australia. It’s where a continental shelf under the ocean drops off into deeper waters. Here, migrating blue whales pass by a resident population of more than 150 orcas. It may be the largest grouping of orcas in the world.

The oceans used to host many more large whales. But in the 1900s, humans killed nearly 3 million of them. As many as 90 percent of blue whales disappeared.

No one knows if large whales played a significant role in orca diets in the past. It’s definitely possible, though, says Pete Gill. He is a whale ecologist at Blue Whale Study in Narrawong, Australia. Orcas and blue whales have been interacting for tens of thousands of years, he points out. “I imagine they have had this dynamic for quite a long time.”

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Power Words

More About Power Words

anatomy: (adj. anatomical) The study of the organs and tissues of animals. Or the characterization of the body or parts of the body on the basis of structure and tissues. Scientists who work in this field are known as anatomists.

attention: The phenomenon of focusing mental resources on a specific object or event.

behavior: The way something, often a person or other organism, acts towards others, or conducts itself.

biologist: A scientist involved in the study of living things.

blue whale: A species of baleen whale (Balaenoptera musculus) that is the largest animal ever known to have existed. They can grow to lengths of 30 meters (almost 100 feet) and weigh up to 170 metric tons.

calf: (plural: calves) The name of young animals in a range of mammalian species, from cattle to walruses.

continental shelf: Part of the relatively shallow seabed that gradually slopes out from the shores of a continent. It ends where a steep descent begins, leading to the depths typical of most of the seafloor beneath the open ocean.

debris: Scattered fragments, typically of trash or of something that has been destroyed. Space debris, for instance, includes the wreckage of defunct satellites and spacecraft.

defense: (in biology) A natural protective action taken or chemical response that occurs when a species confronts predators or agents that might harm it. (adj. defensive)

diet: (n.) The foods and liquids ingested by an animal to provide the nutrition it needs to grow and maintain health. (v.) To adopt a specific food-intake plan. People may adopt a specific diet for religious or ethical reasons, to address food allergies, to control their body weight or to control a disease such as high blood pressure or diabetes.

dinosaur: A term that means terrible lizard. These reptiles emerged around 243 million years ago. All descended from egg-laying reptiles known as archosaurs.

dorsal: The back of something, usually an animal.

ecologist: A scientist who works in a branch of biology that deals with the relations of organisms to one another and to their physical surroundings.

juvenile: Young, sub-adult animals. These are older than “babies” or larvae, but not yet mature enough to be considered an adult.

killer whale: A dolphin species (Orcinus orca) whose name means whale killer. Known as orcas, these animals belong to the order of marine mammals known as Cetacea (or cetaceans).

marine mammal: Any of many types of mammals that spend most of its life in the ocean environment. These include whales and dolphins, walruses and sea lions, seals and sea otters, manatees and dugongs — even polar bears.

mechanism: The steps or process by which something happens or “works.” It may be the spring that pops something from one hole into another. It could be the squeezing of the heart muscle that pumps blood throughout the body. Researchers often look for the mechanism behind actions and reactions to understand how something functions.

pod: (in zoology) The name given to a group of whales that travel together, most of them throughout their life, as a group.

population: (in biology) A group of individuals (belonging to the same species) that lives in a given area.

predation: A term used in biology and ecology to describe a biological interaction where one organism (the predator) hunts and kills another (the prey) for food.

right whale: One of three baleen whale species in the genus Eubalaena. Each tends to live in a different ocean basin. The animals got their name from the opinion of whale hunters that these were the “right” whale to catch. The reasons: Once dead they float, so the hunters won’t lose them at sea; these whales contain lots of the oil and baleen that could be sold in 18thand 19thcentury seaports; and the animals swim slowly and near to shores. They can live more than 50 years (perhaps a century) and grow to about 15.25 meters (50 feet) and some 63 metric tons (140,000 pounds). Those in the Northern Hemisphere were nearly wiped out by whaling. Their numbers remain low.

sharks: A family of primitive fishes that rely on skeletons formed of cartilage, not bone. Like skates and rays, they belong to a group known as elasmobranchs. Then tend to grow and mature slowly and have few young. Some lay eggs, others give birth to live young.

species: A group of similar organisms capable of producing offspring that can survive and reproduce.

weather: Conditions in the atmosphere at a localized place and a particular time. It is usually described in terms of particular features, such as air pressure, humidity, moisture, any precipitation (rain, snow or ice), temperature and wind speed. Weather constitutes the actual conditions that occur at any time and place. It’s different from climate, which is a description of the conditions that tend to occur in some general region during a particular month or season.

whale: A common, but fairly imprecise, term for a class of large mammals that lives in the ocean. This group includes dolphins and porpoises.

Citations

Journal: J.A. Totterdell et al.The first three records of killer whales (Orcinus orca)killing and eating blue whales (Balaenoptera musculus). Marine Mammal Science. Published online January 21, 2022.doi: 10.1111/mms.12906.

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