Over winter and spring, the male establishes and defends a ‘nest’ – usually a hollow beneath a rock. The male turns very dark, from brown to completely black, while defending the nest. When a female is ready to lay eggs, she enters the nest and turns upside-down to lay 1,000–20,000 oval eggs in a close-packed, single layer attached to the nest's ‘ceiling’. The male then fertilises the eggs. The female leaves the eggs in the care of the male, which guards them until they hatch two to four weeks later. Females may lay more than once over the spawning season, and one male may defend the eggs of more than one female.