Why Do Bearded Dragons Puff Up? The Black Beard Display

What is a bearded dragon’s beard?

The “beard” of the central bearded dragon is a pouch of loose skin under the throat, covered with rows of pointed scales. Most of the time it lies flat and looks like a spiny collar. When the lizard displays, small bones and muscles in the throat, called the hyoid apparatus, push the pouch down and outward. The scales then stand out, and the throat looks like a bristling black beard.

Both sexes have a beard, but males have larger ones and display them more often. During the breeding season, male beards can turn almost jet black, while females usually show a paler gray or brownish beard.

How does a bearded dragon puff up?

A full threat display combines several actions:

• Beard expansion: the throat pouch is pushed outward, and its spiny scales stand on end.
• Body flattening: the lizard spreads its ribs sideways and fills its lungs with air, so the body looks wide and flat from above and tall from the side.
• Color change: the beard, and sometimes the head and body, darkens.
• Gaping: the dragon opens its mouth wide to show the pale lining.
• Hissing and lunging: a cornered dragon may hiss softly and make short jumps toward the threat.

Each part makes the lizard seem bigger, rougher or more alarming. To a bird of prey or a snake, a spiny, wide-bodied lizard with an open mouth is a less appealing meal than a small, slim one.

Why do bearded dragons puff up at rivals?

Most beard displays happen between dragons. Adult males defend territories and the best basking perches, and they advertise their status with a dark, expanded beard, a tall stance and fast head-bobbing. A rival that is smaller or less confident usually answers with a slow arm-wave, the submission signal described in Why do bearded dragons wave?.

If the rival does not back down, both males may flare their beards, circle each other, lash their tails and eventually fight, biting at heads and tails. Display usually settles the dispute first, which saves both animals from injury.

Why do male bearded dragons puff up at females?

During the Australian spring and summer, roughly September to March, males court females with an intensely dark beard and vigorous head-bobbing. The black beard is a breeding signal as well as a warning, telling the female that a mature, healthy male is present. A receptive female answers with arm-waves and slow head-bobs.

Why do bearded dragons puff up at predators?

In the wild, central bearded dragons are hunted by birds of prey, goannas (monitor lizards), snakes, dingoes and introduced foxes and cats. Their first defense is to stay still and blend in, or to sprint to cover. When a predator gets close and escape is not possible, the dragon turns to face it and puts on its full display.

This is a bluff. The bearded dragon is harmless to large animals and has only a modest bite, but a sudden change from a slim brown lizard to a wide, dark, spiny, gaping one can make a predator hesitate long enough for the dragon to escape.

Is an open mouth always a threat?

No. Bearded dragons often sit quietly with their mouths open while basking on a hot rock or branch, without any puffing or darkening. This behavior, called gaping, lets moisture evaporate from the mouth and helps the lizard shed extra heat once it is warm enough. A threat gape is different: it comes with an expanded beard, a flattened body and a lizard turned to face the danger.

Is the black beard only about mood?

Not entirely. Bearded dragons change the shade of their skin for more than one reason. Field studies of free-living central bearded dragons have shown that they darken their backs when cool, which helps them absorb sunlight faster, and lighten as they warm up. This is a temperature effect, separate from the social signal of the beard.

The beard itself can also look darker when a dragon is cool or stressed, so a dark throat does not always mean a display. A true display is easy to recognize, because the beard is expanded and usually combined with posture, gaping or head-bobbing. For more on how reptiles manage their temperature, see Are reptiles cold-blooded?.

Which other lizards puff up?

Puffing up is a common lizard defense. In Australia, the frilled lizard, a relative in the same family, opens a huge frill of skin around its neck. Many lizards worldwide inflate their bodies or throats in threat displays, and North American horned lizards puff up to look bigger and harder to swallow. The bearded dragon’s beard is one of the best-known versions of this widespread strategy.