In Cheshire, a fox is poised to pounce on its mate when a badger bursts from a bush. The badger starts chasing the fox, which keeps leaping away, finally distancing itself. Then the fox suddenly turns back, approaches cautiously, and jumps sideways, facing the badger head-on. Back arched, head low, it stops, remains still. After a pause, the badger swiftly resumes the chase, causing the fox to hop around before lunging at its companion and darting off together.
In Orlando, three dolphins are swimming in unison when one forms a perfect bubble ring. Another immediately approaches and blows another ring, which merges with the first to create a larger hoop. The third dolphin appears to attempt to pass through it, completing their improvised choreography.
Animals often engage in play, from the spectacular to the subtle. Hyenas stage mock brawls, cats spin in circles chasing their tails, octopuses play push-and-pull with bottles, dogs bury sticks only to dig them up moments later… Even polar bears have been spotted playing with dogs, grabbing them in what looks like a hug, rolling in the snow, and letting the dogs gently nibble their lips. Such scenes make us grin with delight. But is that all there is to it?
Animal play can seem trivial, even laughable. Often defined as an intrinsically rewarding activity, yet offering no immediate survival benefits, its very existence is puzzling. While it has long been hypothesised that play serves as a rehearsal for adult behaviours, some studies suggest that it might not be crucial to their development. Similarly, although some scholars propose that play allows animals to expend surplus resources (time, energy, neural activity) – which could explain play’s prominence in pets – this does not account for its widespread occurrence in wild species. Play challenges us with its apparent lack of biological necessity.
Albertine and Pippo
As I was writing these paragraphs, my cat Albertine approached my dog Pippo and slowly rose onto her hind legs, wagging her tail while presenting her forepaws. After freezing for a few seconds, she started tapping his lips frantically. Right after, spotting a speck of dust flying around, she hopped up on the table, scattering my pens with a thunderous clatter, then immediately jumped onto my shoulder, clinging as if to a tree, before leaping off to burrow under the sofa, grunting. Watching her, I can’t help but suspect – much as Michel de Montaigne did with his own cat – that she may be playing with me (and us) far more than I am playing with her. And there’s something surprising, even unsettling, about this idea. Because, through their play, animals reveal an inner self we cannot access, one we are quick to dismiss as empty or purely sensory – infinitely more limited than our own. Whether phylogenetically close to us or vastly distant (especially when distant), we imagine animals as prisoners of their instincts, focused solely on survival. Yet play offers more to the spectator than its delightful exuberance: it reveals a freedom and creativity unique to animals, which intrigued Montaigne and challenges us to reconsider our assumptions.
Let’s go back to Albertine. Just before she slapped Pippo, she stood up and wagged her tail. When wagging their tails, cats – unlike dogs – aren’t usually expressing excitement or pleasure, but annoyance. However, when Albertine interacts with Pippo, this behaviour almost always precedes play. It seems to act as a code, signalling the playful nature of what is coming. Today, immediately afterwards, Albertine tapped Pippo without using her claws, touching not his eyes or nose, as she would in a real fight, but his lips. The slaps didn’t hurt him. The apparent agonistic behaviour was diverted from its usual function: the aim was not to injure, but to mimic a fight that was not real. Pippo ‘collaborated’ by opening his mouth, his fangs 5 cm from her skull, yet without biting. Then Albertine started chasing the dust as if it were prey, but this too was theatrical. Her flamboyant leaps would never let her remain unnoticed by real prey. It was all about pretending.
In play, animals use real-world objects and situations to create fictitious ones
Through her energetically costly – albeit certainly pointless – activities, Albertine designed a scenario detached from her present reality: she moved through a simulated world. This playful activity had no obvious function. Albertine seemed to engage in it for its own sake: it looked pleasurable. Hence, play challenges both our philosophical and biological prejudices. Philosophically, animals are generally perceived as sentient, even intelligent, but whose intelligence is entirely devoted to survival. The still-dominant view aligns with the psychologist Frederik Jacobus Johannes Buytendijk’s assertion in 1942 that distinguished humans from animals: ‘Humans do not live unambiguously in an unambiguous world, unlike animals’.
Animals are assumed to be trapped in unequivocal, purely utilitarian relationships with the world. From a biological perspective, especially within evolutionary theory, the traditional approach conceives of nonhuman organisms as genetically programmed machines, their behaviours entirely shaped by natural selection to serve specific functions. Play, however, disrupts both these assumptions. On one hand, in play, animals use real-world objects and situations to create fictitious ones. On the other hand, this activity stands out for its apparent short-term uselessness and even its potential dangers, the conspicuousness of playful movements exposing animals to predators. Remarkably, 22 of the 26 seal pups that died during the observation of the biologist Robert Harcourt were attacked by sea lions while playing. This example rebuts the claim that play, such as that between Pippo and Albertine, is confined to domestic animals, shielded from natural pressures and ‘distorted’ by human influence.
Play is widespread among animals, both domestic and wild, across a vast range of species. Several biologists (including Marc Bekoff, Gordon M Burghardt, John A Byers, Robert Fagen and Paul Martin) have proposed criteria for identifying play. In summary:
- Play lacks apparent short-term benefits.
- It is an activity animals seek for its own sake (it seems pleasurable).
- It involves motor patterns from functional, ‘serious’ contexts used in modified forms (eg, exaggeration, self-handicapping) and altered temporal sequencing.
- Because of its uselessness, play occurs when the animal feels (rightly or wrongly) safe and free from stress.
These criteria have helped identify play in a wide variety of species, from land mammals to cetaceans, birds, reptiles and even fish. It has also been observed in invertebrates: octopuses, spiders and, more recently, flies and bumblebees (apparently fond of rolling marbles).
Albertine’s actions were both exaggerated and versatile: she leapt high, landing on the table in a theatrical skid
How can we understand the omnipresence of this seemingly pointless activity? To begin with, we need to rethink our assumptions and consider that animals may be capable of pretence, and therefore, a form of creativity. The use of play-signals, like Albertine’s gesture to warn Pippo of the falsity of her attack, is common across species and, as in their case, even between species (eg, between dogs and horses). These signals are metacommunicative: they inform the other player that the situation is only a pretence. Through them, we know that animals actively build these simulated situations rather than being misled by illusion or error. Hence play also invites us to recognise that animal behaviour may not be entirely dictated by the struggle for existence and the drive for optimisation – ie, for maximising resources while minimising energy expenditure.
If we embrace this shift in perception and revisit Albertine’s game, we can notice something else. Not only was Albertine creative in shaping her scenario, but she was also inventive in her behaviour. Her actions were both exaggerated and versatile: she leapt high, landing on the table in such a theatrical skid that objects scattered to the floor; she seamlessly transitioned from combat to hunting sequences. Albertine seemed to use this make-believe scenario, full of twists and turns, to explore her behavioural flexibility.
This is why some researchers hypothesise that the prevalence of play in many domestic and wild species, despite its apparent frivolity, may be explained not (so much) by its role in training typical behaviours, but rather by its function in fostering flexibility. Play provides opportunities for animals to test new behaviours that could later prove useful in functional contexts. Play, they suggest, prepares animals to perform novel actions in unexpected circumstances. It is indeed suited for such training, as it suspends the usual practical relationship with the world. Freed from the imperatives of reality, animals do not solely react to environmental stimuli but use them to investigate new potential relationships with their surroundings.
In play, animals can experiment with behaviours that might be ineffective or dangerous in real situations, but without running actual risk. Indeed, the playful situation is only a pretence, while the real-life circumstances are (or are at least perceived as) safe – otherwise, animals would not play. This may explain the sometimes-overdramatic aspect of playful behaviour: animals appear to be trying new things, exploring possibilities. In fact, play combines what computational theory identifies as the three processes of creation:
- Exploring an existing framework, such as a motor sequence, to discover its potential and limits.
- Creating a new combination of elements.
- Transforming the space of possibilities, by altering, adding or removing elements within the sequence.
Albertine’s play exemplifies these processes. She consecutively explored two patterns: fight and predation. She reorganised their usual order (ie, chasing before killing), and even inverted elements within each sequence: she jumped before reaching the prey and hid under the sofa after the chase (despite being highly visible during it). Finally, she transformed typical hunting movements, replacing restrained, stealthy actions like crawling or creeping with showy, exaggerated leaps. Admittedly, these modifications would be ineffective in actual hunting – had the situation been real, Albertine would likely have come home empty-pawed. However, as it was a mock hunt, there was nothing to lose, allowing her to explore new patterns, regardless of their impracticality or risks in real life.
The real predators fictitiously place themselves in a position of subordination
This distance from reality and the exploration of behavioural flexibility occurs in all kinds of play but is particularly remarkable in interspecies play. When Albertine plays with Pippo, she transforms the usual meaning of her movements into shared codes. Her wagging tail is no longer a sign of irritation but signals a game starting – a cue her canine partner, whose tail wags in playful excitement, can readily interpret. Such shifts in meaning are essential due to behavioural differences between the two species. To play together, animals from distinct species must invent shared codes. Barbara Smuts, a primatologist renowned for her research on baboons, also described the playful interactions between her dog Safi and her neighbour’s donkey, Wister. To initiate and maintain play despite their morphological and communicational differences, Wister and Safi, she reported, co-created their own shared signals.
Interspecies play relies on – and, in doing so, reveals – animals’ ability for reciprocal flexibility. Such flexibility is not limited to domestic animals. Interspecies play has been observed in the wild between foxes and badgers, otters and alligators, baboons and jackals, ravens and wolves, and even, as mentioned above, dogs and polar bears. Strikingly, some of these species are involved, in ‘real life’, in predatory relationships, which always threaten to surface during the game. Yet the game pauses this threat, notably through self-handicapping and role reversal. Polar bears, for instance, will roll onto their backs, exposing their abdomen, as if submitting to the dogs. The real predators fictitiously place themselves in a position of subordination, putting the true predatory relationship at a distance.
Interspecies play thus involves modifying existing behaviours and sometimes even creating new ones. Wister, for instance, began imitating Safi by picking up sticks. Similarly, ravens invent motor sequences to engage in play with wolf pups. The relationship between ravens and wolves is a well-known mutualistic one: ravens follow wolves to access carcasses more efficiently, while wolves benefit from the ravens’ alerts to both potential prey and predators. However, this relationship, although widespread, does not develop automatically whenever the two species cohabit. It seems to rely on bonds established during their juvenile stage, notably through play. In Yellowstone National Park, for example, some ravens have invented a game where they pick up sticks, catch them in their talons, and fly in circles above wolf cubs, prompting the cubs to leap to catch them.
But aren’t these descriptions anthropomorphic? How can we be certain that animals truly play or invent?
As regards play, the criteria outlined above are operational, helping us identify it across species. Some might argue that the behaviours described here bear little resemblance to human play. Yet human play takes many forms – from children’s pretend play (not so far removed from some animal play), to chess, rough-and-tumble games, or football – all fitting the proposed definition despite their differences. One could object that this definition lacks certain features, such as explicit rules. However, rules are not always present, especially in children’s play. Above all, assuming play is unique to humans, and that its definition should exclude nonhuman animals, is no more justified than assuming it is universal across species and tailoring a definition accordingly. The criteria developed by play biologists strike a balance: broad enough for cross-species comparison, yet narrow enough to distinguish play from closely related behaviours, like exploration.
Her expertise and familiarity with Safi and Wister ensured that the behaviours she identified were indeed inventions
The question of invention is similar. Depending on the definition, we can either restrict inventiveness to humans (or to a few phylogenetically close species) by linking it to specific cognitive processes, or adopt a more inclusive framework enabling comparative studies. In the latter case, the definition must be precise enough to distinguish inventions from other behaviours (including in humans), but comprehensive enough to encompass several different species (including nonhuman ones). Therefore, it should rely less on presumed intentionality or neural mechanisms than on the relationship between the behaviour under study and the typical repertoire of the individual and its group.
An invention could thus be defined as a behaviour outside the animal’s usual repertoire and not learnt from others – unprecedented, at least for that individual and its social group (indeed, inventions can arise in different groups, just as René Descartes and Christiaan Huygens independently developed a lens to avoid spherical aberrations, Gottfried Wilhelm Leibniz and Isaac Newton infinitesimal calculus, Charles Darwin and Alfred Russel Wallace the theory of evolution). Invention is characterised by unpredictability, often marked by the researcher’s surprise – a hallmark that requires careful control of subjective biases through accurate knowledge of observed individuals and their habitual behaviours. This is what makes Smuts’s seemingly anecdotal observation so valuable: her ethological expertise and familiarity with Safi and Wister ensured that the behaviours she identified as new were indeed inventions. Invention in humans does not require additional criteria: it merely involves creating something new. One might argue that an invention must prove useful and be adopted by others, but in this case we speak instead of an innovation (a distinction also applied in animal behaviour literature).
In addition to the question of anthropomorphism, there is another, perhaps more decisive one: why should we care? Admittedly, animal play may not be as meaningless as once thought and reveals capacities we believed animals lacked. But why does that matter? On one hand, it challenges our sense of human exceptionality: neither play nor invention are unique to us. To identify what, if anything, sets us apart from other animals, we may need to look elsewhere – perhaps at our cumulative culture, which not only expands our repertoire (as in animals) but also refines and complexifies our innovations across generations. On the other hand, it encourages us to pay attention to behaviours we might otherwise dismiss as frivolous or perplexing. In Animal Play Behavior (1981), Fagen describes play as ‘irritating’, not because of its ‘perceptual incoherence as such’, but because ‘play taunts us with its inaccessibility. We feel that something is behind it all, but we do not know, or we have forgotten, how to see it.’ We struggle to make sense of play because it resists our theoretical frameworks, compelling us to reassess the utilitarian assumptions that underpin them.
It may even engage us to amend our theory of evolution. Indeed, play reveals that animals can develop new behaviours, and therefore new relationships with their environment – some of which might be unintended beneficial side-effects of play. This also means animals can influence the selective pressures exerted on them. For instance, through inventive play, ravens and wolves forge lasting bonds that facilitate their access to resources and improve their chances of survival and reproduction. Many examples suggest that animal innovations aid adaptation. A striking case is that of kestrels in Mauritius that survived the arrival of macaques – which systematically knock their nests from trees – by inventing a method of nesting on cliffs. As Darwin already emphasised (something that ‘orthodox’ evolutionary theory, relying on optimisation algorithms, seems to have forgotten), the struggle for existence, driving natural selection, is nothing other than the way organisms interact with their environment and others. A genetic variant has no value unless it benefits an organism’s interactions with its surroundings. Consequently, when an animal invents a behaviour that proves useful, it changes how it is affected by environmental pressures. And, if the behaviour spreads, contributing to the culture of the population, it can even reshape selective pressures for future generations, transforming evolutionary trajectories.
Could the most playful species also be the most capable of meeting ecological challenges?
Recent studies have highlighted the link between animal innovations and evolutionary change. One well-documented case is birdsongs. In many bird species, songs are learnt and form part of their local cultural heritage. In other words, they have been invented, with each population having its own song patterns. And the greater the difference between the songs, the harder it becomes for males from one population to mate with females from another, as they don’t know the local ‘dialect’. Indeed, populations with different dialects also seem to constitute distinct genetic subspecies, hinting at a speciation process sparked, or at least accelerated, by cultural diversity.
Another example involves black rats, which developed a technique for opening pinecones. This innovation gave them access to a new resource and enabled them to invade nearby forests. It is reasonable to hypothesise that this environmental shift will, over generations, lead these rats to evolve differently from their urban counterparts, as they now face distinct selective pressures – a change initiated by their pinecone invention. Moreover, acquiring this new technique imposes a cost on the rats, requiring the effort to invent or learn. This means that, if a genetic variant arose in the population that made the behaviour easier to develop and less costly to acquire, it would likely be selected – individuals carrying the variant would leave more offspring inheriting it. Therefore, innovations can alter selective pressures and, if the right genetic variations emerge, drive evolutionary change – a process known as the Baldwin effect.
If invention promotes the animals’ adaptation to new conditions and, in some cases, enables evolutionary change, and if play reveals their capacity for invention – and even appears to be the activity par excellence through which animals develop their inventiveness – should we go further and ask: could the most playful species also be the most capable of meeting ecological challenges? Could play itself sometimes drive adaptation and evolution? Some researchers have proposed this hypothesis but, for now, it lacks empirical evidence – or rather, empirical research. It is almost as if the hypothesis were too seductive for the gravitas of scientific enquiry, as though scientists preferred to conceal the fact that their research is driven less by the prospect of useful solutions than by the sheer pleasure of discovery.
The exploration and potential corroboration of this hypothesis could, nonetheless, offer a glimpse of another way of living with other animals – one not based on hierarchy or exploitation, but on playful relationships. Like Pippo and Albertine, Safi and Wister, ravens and wolves, we could perhaps co-create with other species the conditions for a shared world. This would not mean simulating shared activities, as in typical play, but drawing from interspecific play the effort to understand other species – an effort that could foster real collaborations, or at least ones that are realisable because they are desirable.
