Short answer: Animals yawn for many of the same reasons people do. The leading theory is that a yawn’s deep breath and wide jaw stretch help cool the brain and shift the body between states such as sleep and alertness. Some animals also use yawns to communicate: stress in dogs, threat displays in baboons, and group synchrony in social species.
Yawning is one of the oldest behaviors in the animal kingdom. It appears in almost every vertebrate studied, from mammals and birds to reptiles, amphibians and fish, which suggests it serves a basic biological purpose. Here is what scientists have learned. (For humans specifically, see why do we yawn.)
Key facts at a glance
- Yawning has been observed in mammals, birds, reptiles, amphibians and fish.
- Across mammals, species with larger brains and more neurons tend to yawn longer, which supports the brain-cooling theory.
- Contagious yawning has been reported in chimpanzees, bonobos, wolves, dogs and some birds such as budgerigars.
- Dogs can yawn in response to human yawns.
The main theories for why animals yawn
1. Brain cooling
A yawn pulls in a large breath of air and stretches the jaw, which increases blood flow to the head. Researchers led by psychologist Andrew Gallup propose that this exchange helps cool the brain. The theory predicts that yawning should depend on air temperature. In a 2009 study, budgerigars yawned more when the room was warming toward body temperature than when it was cooler, which is consistent with that idea.
2. State change: waking up and winding down
Animals often yawn right before sleep, right after waking, and before switching activity, for example when a predator starts to prepare for a hunt. Yawning may help the body transition between states of arousal.
3. Communication
In some species, yawns are signals:
- Baboons and macaques: males often yawn widely to show off their large canine teeth as a threat display.
- Dogs: dogs often yawn in tense situations, such as at the vet or when scolded. Many trainers read this as a stress or “calming” signal.
4. Physical reset
Some “yawns” have a mechanical job. Snakes open their jaws wide after swallowing prey, realigning their jaws and helping the windpipe clear. Fish gape to move water over their gills.
Why do dogs yawn?
Dogs yawn when they are tired, but also when they are stressed, excited or uncertain. And yes, dogs can catch yawns from people. A 2008 study found that many dogs yawned after watching a human yawn, and later research suggested dogs are more likely to catch yawns from their owners than from strangers.
Why do cats yawn?
Cats yawn most often around sleep, and they sleep a lot. Their big yawns usually come with a full-body stretch as they transition from resting to moving. Unlike dogs, cats show little evidence of contagious yawning.
Why do birds yawn?
Birds yawn much like mammals: a wide gape, a deep breath and sometimes a stretch. Research on budgerigars found that yawning in birds is linked to temperature, and budgerigars even showed a form of contagious yawning with each other.
Is contagious yawning a sign of empathy?
This is still debated. In humans and chimpanzees, contagious yawning is often stronger between close friends or family, which some researchers link to social bonding and empathy. Others argue it may be a simpler form of copying behavior. Either way, it appears mainly in social species that benefit from moving and resting together.
Frequently asked questions
Do all animals yawn?
Almost all vertebrates yawn, including mammals, birds, reptiles and fish. Invertebrates such as insects do not yawn in the same way.
Why do mammals yawn?
Mostly to regulate brain temperature and alertness, especially around sleep. Some mammals also use yawns as social signals.
Can animals catch yawns from humans?
Dogs can. Studies show many dogs yawn after watching a person yawn, especially their owner.
Is yawning a sign of stress in dogs?
It can be. Frequent yawning in a tense situation often signals stress, while a yawn at bedtime just means your dog is sleepy.
Sources
- Gallup, A. C. et al. (2016). “Yawn duration predicts brain weight and cortical neuron number in mammals.” Biology Letters.
- Gallup, A. C., Miller, M. L. & Clark, A. B. (2009). “Yawning and thermoregulation in budgerigars.” Animal Behaviour.
- Gallup, A. C. et al. (2015). “Contagious yawning in budgerigars.” Animal Cognition.
- Romero, T. et al. (2013). “Familiarity bias and physiological responses in contagious yawning by dogs.” PLoS ONE.
- Joly-Mascheroni, R. M., Senju, A. & Shepherd, A. J. (2008). “Dogs catch human yawns.” Biology Letters.
- Campbell, M. W. & de Waal, F. B. M. (2011). “Ingroup-outgroup bias in contagious yawning by chimpanzees.” PLoS ONE.