Orcas off the west coast of North America are grooming each other with kelp, in a rare sighting of marine mammals manufacturing and using tools.

For several years, scientists have been keenly observing 80 endangered killer whales in the segment of the Pacific Ocean between British Columbia and Washington state. To get a bird’s eye view of the whales’ lives, the researchers also tracked them with drones.

While poring over footage from summer 2024, they noticed that the orcas were manoeuvring strands of kelp in odd ways. It was “really weird”, says at the in Washington state, “but the whales, they do weird things all the time”.

In the footage, the orcas can be spotted breaking off kelp stalks near where they meet the rock bed by grabbing them with their teeth and jerking their heads back and forth. The short, snapped-off segments were roughly equivalent in length to that of the whale’s beak-like face. Over and over again, the orcas appear to consistently target just that specific segment of the algae, not other random parts of kelp.

After breaking off a strand, a whale would then sandwich the kelp between their head and the bodies of other whales in the pod, rubbing and rolling it onto each other’s sides. They take turns cleaning each other with the kelp, sometimes grooming each other for up to 12 minutes.

“What’s cool is that they don’t have any kind of hand-like appendages, and so they’re doing all of this using very deliberate movements of their body,” says John.

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Orcas are known to rub themselves against kelp on their own, known as “kelping”. This could be a social variation of that behaviour. “We know that the social bonds in this population are super, super strong, and we know that contact is one way that they reinforce those bonds,” says John.

The behaviour was present across all ages and sexes, though the data suggests the whales that were most closely related and those closer in age were more likely to “kelp” together. Crucially, this may be a form of whale hygiene, says John, as the team found that orcas are more likely to scrub each other with kelp if they are shedding their skin.

It might still be too early to confirm whether this skincare has health benefits, says at Griffith University, Australia. He would like to see the researchers cross-reference the orcas’ skin bacteria with the properties of the kelp to see if they match.

“It totally makes sense to me that they are seeking out anything that the ocean could offer to help them with potential reduction in skin infections,” says Meynecke. He suspects this is a widespread behaviour among other orca populations and whale species.

Bonobos are quick to help a person who doesn’t know what they know, a sign that they can deduce the mental states of others.

The capacity to think about what others are thinking, known as , is an essential skill that allows humans to navigate their social worlds. It enables us to recognise that someone may hold different beliefs or perspectives to our own, underpinning our ability to understand and help others appropriately.

The question of whether our closest living relatives also have theory of mind has been hotly debated for decades. Despite some , non-human great apes seem to have some aspects of this capacity, suggesting it is more evolutionarily ancient than once thought. For example, wild chimpanzees that see a nearby snake, albeit a fake one, seem to call out to they know haven’t already seen it.

But we have been missing clear evidence from controlled settings that primates can track a perspective that differs from their own and then act upon it, says at Johns Hopkins University in Maryland.

To investigate this, Townrow and , also at Johns Hopkins University, tested if three male bonobos at the Ape Initiative research centre in Iowa could identify ignorance in someone they were trying to cooperate with, and then gesture to them to help solve the task.

On a table between the bonobo and an experimenter were three upturned plastic cups. A second researcher placed a barrier between the experimenter and the cups, then hid a treat, like a juicy grape, under one of them.

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In one version of the experiment, the “knowledge condition”, a window in the barrier allowed the experimenter to watch where the treat was placed. In the “ignorance condition”, their view was completely blocked. If the experimenter found the food, they would give it to the bonobo, providing a motivation for the apes to share what they knew.

Townrow and Krupenye looked at whether the ape pointed at the cup, and how quickly they pointed, after the barrier had been removed over 24 trials for each condition.

They found that, on average, the bonobos took 1.5 seconds less time to point and pointed in approximately 20 per cent more trials in the ignorance condition. “This shows that they can actually take action when they realise that somebody has a different perspective from their own,” says Krupenye. It appears that bonobos understand features of what others are thinking that researchers have historically assumed they didn’t comprehend, he adds.

This simple yet powerful research gives experimental support to existing findings from wild apes, says at Durham University, UK. However, she warns that the findings may not apply to all bonobos because the study animals were raised in human-oriented environments. But that doesn’t detract from the results demonstrating that a capacity is there, she adds.

Indeed, finding this capacity in these three bonobos indicates that the potential exists within their biology and, very likely then, the biology of our common ancestor as well, says Krupenye.

“It suggests that our ancient human relatives likely also had these abilities and could use them to bolster cooperation and coordination with one another,” says at the University of California, Berkeley. “By understanding when someone may be ignorant, especially about evolutionarily critical information like the location of food, our ancestors could have used these capacities to communicate and coordinate more effectively with their social partners.”

Dogs seem to understand that words represent specific objects, recordings of their brain activity suggest.

Although some dogs can fetch a wide range of different objects on command, few do well on such tests in the lab. In addition, it is unclear if dogs understand words as object names, rather than instructions.

To explore this question, at Eötvös Loránd University in Budapest, Hungary, and her colleagues tested 18 dogs from a wide range of breeds, including Border collies, toy poodles and Labrador retrievers.

Their owners chose five objects familiar to each dog. In the test, they said the name of an object and then showed the dog either the named object or a different object.

Each dog’s brainwaves were monitored via electroencephalography (EEG) to see whether there was a difference in activity when the dog’s owner said “ball”, but showed a stick, for example, compared with when the word and object were the same.

“The idea was that if dogs understand the meaning of the words, their brain responses will differ between the presentation of matching and mismatching objects,” says Boros.

The researchers found that the EEG signals were different when the objects didn’t match and the effect was stronger for words that individual dogs knew well. This is similar to results seen in humans and suggests that dogs know that certain words represent certain objects.

“The most important realisation of this study is not only that non-humans are capable of understanding words referentially, but this capacity seems to be generally present in dogs as well,” says Boros. “This study demonstrates that dogs may understand more than they show.”

No breed appeared to show a greater language ability than any other, says Boros.

at the University of Adelaide, Australia, says the study adds to the knowledge of dog cognition.

“I think dogs both understand more and less than what we realise,” says Hazel. “This research shows dogs appear to make a mental representation of a word they know – for example a ball – which is not at all surprising to most dog owners who know how their dogs understand some words.”

On the other hand, she says, many dog owners anthropomorphise their pets and attribute emotions and comprehension abilities to them that don’t exist.

“Dog cognition is now one of the most studied areas around the world,” says Hazel. “I love all the research on dogs, but would love to see more on other animals we live closely with – cats, rabbits, horses.”