Killer whales and dolphins have been working together to hunt salmon in the northern Pacific Ocean, an unexpected finding that further reveals the complex social lives of marine mammals.

Video cameras and sensors attached to nine killer whales – also known as orcas – showed four of them diving with numerous Pacific white-sided dolphins towards Chinook salmon hiding in the depths off northern Vancouver Island. Three more whales were observed by drone. The orcas ate the salmon, while the dolphins scavenged the scraps.

“They were cooperatively foraging,” says at Dalhousie University in Canada. “You could anthropomorphise it and say that they’re being friends for hunting purposes.”

Also known as king salmon, Chinook salmon can grow more than a metre long and are often too big for dolphins to eat.

But northern Vancouver Island whales are messy eaters and often tear fish apart to share with family, leaving blood, scales and fragments for dolphins to consume. The dolphins help whales “scout” out salmon, the researchers believe.

Six out of the 12 whales interacted with the dolphins, orienting to face them a combined total of 102 times in the videos. Four dived with dolphins as deep as 60 metres, where it’s dark and salmon can take cover among rocks and crevasses.

Free newsletter

Sign up to The Weekly

Sign up to newsletter

While both species emitted clicks and buzzes, the sensor data revealed that whales often reduced their echolocation – apparently to “eavesdrop” on the dolphins. Since echolocation is narrowly focused like a spotlight, a large number of dolphins scanning the water may improve a whale’s chances of finding fish, says Fortune.

“It’s like turning on the high beams” on a car, she says, “and the light is the sound.”

Scientists have previously found inter-species cooperation such as fish leading an octopus toward crustaceans, or honeyguide birds leading a human to bee colonies. But killer whales’ scientifically observed interactions with other species have typically been to prey on or harass them.

Orcas around the Iberian peninsula have recently rammed and sunk half a dozen sailboats, although scientists say it’s more likely than attacking them.

at Ocean Wise, a global conservation organisation, argues dolphins in the study are stealing scraps rather than cooperating with whales. In a she and her colleague published this year, drone footage in the same area showed whales appearing to ignore, play with or, in one case, lunge at dolphins. Her study concluded dolphins were mainly seeking protection from a particular population of mammal-eating orcas known as Biggs’ killer whales, which avoid the resident killer whales.

When did life begin on Earth? New evidence reveals a shocking story

Fossils and genetics are starting to point to life emerging surprisingly soon after Earth formed, when the planet was hellishly hot and seemingly uninhabitable

“We observed no clear evidence of benefits to the killer whales,” says Visona-Kelly.

last month reported 30 to 40 Pacific white-sided dolphins circling an emaciated killer whale known to researchers as I76, who dived and didn’t re-emerge. This suggested the dolphins may have “exhausted I76 so that he was unable to return to the surface”, according to the paper.

at the University of St Andrews, UK, says the new research convincingly shows cooperation, regardless of whether the whales could interpret dolphin echolocation or were simply attracted to the commotion as a possible sign of fish.

“These animals are smart and behaviourally flexible,” he says. “We’ll see all kinds of interactions between killer whales and dolphins, everything from the killer whales eating them to playing with them to cooperating with them.”

Humpback whale songs have statistical patterns in their structure that are remarkably similar to those seen in human language. While this doesn’t mean the songs convey complex meanings like our sentences do, it hints that whales may learn their songs in a similar way to how human infants start to understand language.

Only male humpback whales (Megaptera novaeangliae) sing, and the behaviour is thought to be important for attracting mates. The songs are constantly evolving, with new elements appearing and spreading through the population until the old song is completely replaced with a new one.

“We think it’s a little bit like a standardised test, where everybody’s got to do the same task but you can make changes and embellishments to show that you’re better at the task than everybody else,” says at Griffith University in Gold Coast, Australia.

Instead of trying to find meaning in the songs, Allen and her colleagues were looking for innate structural patterns that may be similar to those seen in human language. They analysed eight years of whale songs recorded around New Caledonia in the Pacific Ocean.

The researchers started by by creating alphanumeric codes to represent every song from every recording, including around 150 unique sounds in total. “Basically it’s a different grouping of sounds, so one year they might do grunt grunt squeak, and so we’ll have AAB, and then another year they might have moan squeak grunt, and so that would be CBA,” says Allen.

Once all the songs had been encoded, a team of linguists had to figure out how best to analyse so much data. The breakthrough came when the researchers decided to use an analysis technique that applies to how infants discover words, called transitional probability.

Free newsletter

Sign up to The Earth Edition

Sign up to newsletter

“Speech is continuous and there are no pauses between words, so infants have to discover word boundaries,” says at the Hebrew University of Jerusalem. “To do this, they use low-level statistical information: specifically, sounds are more likely to occur together if they are part of the same word. Infants use these dips in the probability that one sound follows another to discover word boundaries.”

For example, in the phrase “pretty flowers”, a child intuitively recognises that the syllables “pre” and “tty” are more likely to go together than “tty” and “flow”. “If whale song has a similar statistical structure, these cues should be useful for segmenting it as well,” says Arnon.

Using the alphanumeric versions of the whale songs, the team calculated the transitional probabilities between consecutive sound elements, making a cut when the next sound element was surprising given the previous one.

“Those cuts divide the song into segmented sub-sequences,” says Arnon. “We then looked at their distribution and found, amazingly, that they follow the same distribution found across all human languages.”

In this pattern, called a Zipfian distribution, the prevalence of less common words drops off in a predictable way. The other striking discovery is that the most common whale sounds tend to be short, just as the most common human words are – a rule known Zipf’s law of abbreviation.

at the University of Sydney, who wasn’t involved in the study, says it is a novel way of analysing whale song. “What it means is that if you analyse War and Peace, the most frequent word will be twice as frequent as the next and so on – and the researchers have identified a similar pattern in whale songs,” he says.

Team member at the University of Edinburgh, UK, says he didn’t think the method would work. “I’ll never forget the moment that graph appeared, looking just like the one we know so well from human language,” he says. “This made us realise that we’d uncovered a deep commonality between these two species, separated by tens of millions of years of evolution.”

However, the researchers emphasise that this statistical pattern doesn’t lead to the conclusion that whale song is a language that conveys meaning as we would understand it. They suggest that a possible reason for the commonality is that both whale song and human language are learned culturally.

“The physical distribution of words or sounds in language is a really fascinating feature, but there’s a million other things about language that are just entirely different from whale song,” says Enfield.

Dr Dolittle machines: How AI is helping us talk to the animals

Pattern-seeking artificial intelligence promises a new way to decode animal languages from dog to whale. Our relationship with our furry and flippered friends may never be the same

published this week, at Stony Brook University in New York found that other marine mammals may also have structural similarities to human language in their communication.

Menzerath’s law, which predicts that sentences with more words should be composed of shorter words, was present in 11 out of 16 cetacean species studied. Zipf’s law of abbreviation was found in two out of five species where available data made it possible to detect.

“Taken together, our studies suggest that humpback whale song has evolved to be more efficient and easier to learn, and that these features can be found at the level of notes within phrases, and phrases within songs,” says Youngblood.

“Importantly, the evolution of these songs is both biological and cultural. Some features, like Menzerath’s law, may emerge through the biological evolution of the vocal apparatus, whereas other features, like Zipf’s rank-frequency law [the Zipfian distribution], may require the cultural transmission of songs between individuals,” he says.

Dolphins in the Gulf of Mexico are inhaling microplastics, which could lead to lung problems.

Researchers at the College of Charleston in South Carolina carried out routine catch-and-release health assessments on five bottlenose dolphins (Tursiops truncatus) from Sarasota Bay, Florida, and six from Barataria Bay, Louisiana, in May and June 2023.

As part of the checks, they held a petri dish above the animals’ blowholes, looking for any tiny bits of plastic in their breath.

To make sure these dishes weren’t simply picking up microplastics floating in the air anyway, the researchers held a second petri dish away from the blowholes to collect control samples.

They found that all of the dolphins exhaled microplastics. Fifty-four such pieces were collected in total, each smaller than 500 microns.

This shows that dolphins are breathing in microplastics, says team member . “These particles are everywhere, regardless of urbanisation and human development.”

Dziobak expects similar results would occur in other parts of the world. “Microplastics are super small and super lightweight, which makes them easy to transport,” she says. “Some researchers have shown microplastics can travel through the air for thousands of miles.”

The team didn’t investigate whether these particles were harming the dolphins, but previous research suggests they could be.

Is cleaning up the Great Pacific Garbage Patch worth the effort?

Efforts are underway to tidy up the ocean's biggest plastic hotspot. But this cleanup operation could be damaging a unique ecosystem and doing little to stop the overwhelming plastic problem

“What we know from human studies is that inhaling microplastics can lead to lung inflammation and other respiratory problems” says Dziobak. “Since we observed similar particles in the exhaled breath of dolphins as have been reported in humans, dolphins might also be at risk for lung problems.”

at the University of Adelaide in Australia says she would be interested to know exactly how these microplastics could be impacting dolphins. “A lot of research indicates that although health impacts are known to occur, the microplastics have to contaminate the animal in quite high concentrations,” she says.

“Finding microplastics in marine species is now unfortunately a norm, and most specimens that are investigated commonly have them. Dolphins are often an indicator of marine ecosystem health, so this finding supports the fact that microplastics really are ubiquitous.”

The Amazon basin was once home to freshwater dolphins that grew up to 3.5 metres long – making them the largest river dolphins known to science.

Researchers made the surprise discovery during a 2018 expedition in Peru, says at the University of Zurich in Switzerland. The team saw the animal’s fossilised skull poking out of a river embankment and knew right away it was a dolphin. Close analysis confirmed the giant skull was unlike any ever found.

The researchers have now named the new species Pebanista yacuruna. The name honours a mythical aquatic people – the Yacuruna – believed to inhabit underwater cities in the Amazon basin.

The 16-million-year-old fossil was unearthed in a region that was once covered by a lake that was “insanely big – almost like a little ocean in the middle of the jungle”, says Benites-Palomino. Based on the small size of the ancient dolphin’s eye sockets and its large teeth, he says P. yacuruna was probably a predator with poor eyesight. It relied heavily on echolocation to find fish. “We know that it was living in really muddy waters because its eyes started to reduce in size,” says Benites-Palomino.

Because the fossil was found in the Amazon basin, the researchers expected its closest living relatives to be modern Amazon river dolphins. Instead, they found P. yacuruna was more closely related to river dolphins of South Asia. Like them, this ancient species has raised crests on its skull that improved its ability to echolocate.

P. yacuruna may have been driven extinct during a broader ecological shift, says Benites-Palomino. “Around 11 to 12 million years ago, this mega wetland system started to drain, giving way to the modern Amazon. A lot of species disappeared at that moment, and that might also have been the fate of this giant dolphin.”