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Why do male tuatara inflate their bodies and raise their crests?
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tuatara
The species is the sole living member of the reptile order Rhynchocephalia.
Male tuatara inflate their bodies and raise their crests as part of their social and reproductive behaviors, specifically for territorial defense and courtship.1
During the mating season, a male uses these displays to defend his territory against other males. In these confrontations, the physical enlargement is often accompanied by head-shaking, mouth-gaping, and sometimes aggressive chasing or biting.1
When interacting with a female, the male performs a similar display—inflating his body and erecting his spines—to initiate courtship. This body enlargement is further accentuated by a stilted, stately walk as he circles the female before mating.1