The tuatara lives in burrows, either digging one itself or sharing the burrow of a nesting seabird (2) (4) (8). A nocturnal species, the tuatara emerges from its burrow at night to feed, but it may also come out to bask in the sun during the day (2) (3) (8) (9). This reptile has relatively few natural predators, although it may potentially be taken by birds of prey, kingfishers and gulls (9). If attacked, the tuatara is able to shed its tail and then grow a new one (8) (10).
A ‘sit and wait’ predator, the tuatara generally waits for prey to approach (4) (18), and it hunts mainly by sight (2). Its diet includes a variety of small animals, particularly invertebrates such as beetles, crickets and other large insects. It also eats spiders, snails, worms and small lizards, and will even take the eggs and chicks of seabirds (2) (4) (8) (9) (18), as well as occasional adult birds and some carrion (8) (18).
Most prey is seized in the tuatara’s mouth and crushed between its jaws. Small prey may be eaten whole, but larger animals may be killed by persistent biting and then gnawed (18). The tuatara has a unique jaw motion which gives its teeth a shearing, sawing action, allowing it to process food more efficiently (2) (9) (19).
The tuatara mates in the summer, between January and March (2) (4) (9). At this time, males become territorial and will attempt to warn off intruders by inflating their bodies and raising their crests. Aggressive encounters may also involve head shaking, opening and closing the mouth, and sometimes chasing and biting (3) (4) (7). When courting a female, the male tuatara erects its crest and circles the female in a slow, exaggerated, stiff-legged walk (3) (4) (10).
The female tuatara does not lay her eggs until the spring, from October to December (2) (3) (4) (8) (9). At this time, the female chooses a suitable nesting site, typically in an open, sunny area on a warm, north-facing slope, and digs a shallow hole (4) (9). Up to 18 or 19 oval, soft-shelled eggs are laid, and the female then back-fills the hole and may cover it with leaves and grass (4) (8). The female tuatara may guard the nest for a few days to prevent other females digging it up (4) (20), but the eggs are then abandoned (2) (8) (9).
The tuatara’s eggs hatch after 11 to 16 months (3) (9), one of the longest incubation periods known for any reptile (2) (8). The newly hatched tuatara are active by day for the first two months of life, only later starting to burrow and becoming nocturnal (2) (9) (10). As in many reptiles, the sex of the tuatara is determined by the temperature at which the eggs are incubated (4) (9), but this species is unusual in that higher temperatures produce males and lower temperatures produce females, rather than the other way around (2) (21) (22).
Tuatara grow slowly and do not reach sexual maturity until they are around 9 to 13 years old (2) (23). Growth may continue for many more years, and the tuatara can potentially live to over 60 years old (7) (23), or possibly even to over 100 (2) (8). As well as developing slowly, the tuatara also reproduces very slowly, and females are thought to lay eggs only once every four years on average (3) (4) (9). Tuatara on North Brother Island breed even more slowly, producing eggs only around once every nine years (24), and laying relatively small clutches of three to eight eggs (24) (25).