Tuatara (Sphenodon punctatus): New Zealand's Living Fossil

A reptile, but not a lizard

At first glance a tuatara looks like a stocky, spiny lizard, and when a skull reached the British Museum in 1831 it was described as one. In 1867 the zoologist Albert Günther noticed that its skeleton differed from lizards in many ways, and he placed it in an order of its own, Rhynchocephalia, meaning “beak heads”, after the beak-like tip of the upper jaw.

Today the tuatara is recognized as the sole survivor of that order. Its closest living relatives are the squamates, the group that contains lizards and snakes, and together they form the Lepidosauria. Genome studies suggest the two lineages split around 250 million years ago. Rhynchocephalians were once the most common small reptiles in many parts of the world, but they declined during the Cretaceous and disappeared everywhere except New Zealand. What sets the tuatara apart is explained in Is a tuatara a lizard?

The name tuatara comes from the Māori language and means “peaks on the back”, a reference to its crest. Since 2009 scientists have recognized just one species. The small, olive-brown tuatara of North Brother Island in Cook Strait, once treated as a second species (Sphenodon guntheri), is now considered a subspecies.

Appearance: how to recognize a tuatara

Tuatara are heavy-bodied reptiles with a large head, strong legs and a thick tail. Their color ranges from olive green through gray and brown to brick red, often mottled and sprinkled with small pale spots, and an individual’s color can change over its lifetime. The skin is covered in small, grainy scales. Adults shed it about once a year, juveniles three or four times.

The most striking feature is the crest of soft, triangular spines running down the neck and back. It is much larger in males, which can stiffen it during displays and fights. Males also have a narrower belly than females.

Look closely at the head and you will see more differences from a lizard. There is no ear opening and no visible eardrum, although tuatara can hear low-pitched sounds. The tip of the upper jaw forms a chisel-like point. Inside the mouth are two rows of teeth in the upper jaw and one in the lower jaw, which slots between them when the mouth closes. These teeth are fused to the bone and never replaced, so they slowly wear down with age.

Hatchlings have one more unusual feature: a third eye on top of the head. This parietal eye has a lens and a simple retina and shows as a translucent patch, but after four to six months it is covered by scales and pigment. It probably helps to set daily and seasonal rhythms rather than to form images. The tuatara’s parietal eye is the most developed of any living four-legged animal; see Do iguanas have a third eye? for how it compares with that of lizards.

How big do tuataras get?

Tuatara are New Zealand’s largest reptiles. Males are clearly bigger than females, reaching about 61 cm (24 in) from snout to tail tip, while females measure about 45 cm (18 in). Some sources cite lengths of up to 80 cm (31 in), but animals that large are exceptional.

Adult males usually weigh up to about 1 kg (2.2 lb), and the heaviest reach about 1.5 kg (3.3 lb). Females weigh up to about 0.5 kg (1.1 lb).

Habitat and range

Tuatara once lived across both main islands of New Zealand, and their bones still turn up in caves and sand dunes. They had vanished from the mainland by the time Europeans arrived, mainly because of the Polynesian rat, or kiore, which eats eggs and hatchlings. For more than a century wild tuatara survived only on about 32 offshore islands free of introduced mammals, off the northeast coast of the North Island and in Cook Strait and the Marlborough Sounds.

These islands are often steep and windswept, with coastal forest and scrub and dense colonies of burrowing seabirds such as fairy prions, petrels and shearwaters. Tuatara shelter in the seabirds’ burrows or dig their own, and the birds’ droppings enrich the soil and feed the beetles and other invertebrates that tuatara eat. The largest population, on Takapourewa (Stephens Island) in Cook Strait, numbers in the tens of thousands.

Since the 1990s, rats have been cleared from many islands, and tuatara have been returned to islands and to fenced mainland sanctuaries. The first mainland release was at Zealandia in Wellington in 2005, and a wild-hatched youngster was found there in 2009. More detail is in Where do tuataras live?

What do tuataras eat?

Tuatara are sit-and-wait predators that feed mainly on invertebrates. Beetles, crickets, wētā (large flightless insects related to crickets), spiders, millipedes, earthworms and snails make up most of the diet. They also eat lizards, frogs where present, and the eggs and chicks of seabirds. On some islands, fairy prion chicks and eggs are an important food in summer. Adults sometimes eat young tuatara.

A hunting tuatara waits motionless until prey moves, then lunges. Its jaw is built for shearing: after the mouth closes, the lower jaw slides forward, so the teeth saw through tough insect shells and even small bones. Thanks to its slow metabolism, a tuatara needs far less food than a bird or mammal of similar size. Old animals whose teeth have worn down switch to softer prey such as worms, larvae and slugs.

Behavior: a reptile of cool nights

Adult tuatara are mostly nocturnal, hunting at night and resting in burrows by day, though they often bask in the sun near the burrow entrance to warm up. Hatchlings are more active by day, probably to keep out of the way of cannibalistic adults.

What sets the tuatara apart from almost every other reptile is its tolerance of cold. Tuatara remain active at temperatures as low as about 5 °C (41 °F), and their preferred body temperature of about 16–21 °C (61–70 °F) is the lowest known for any reptile. Heat is the bigger danger: temperatures above about 28 °C (82 °F) are generally fatal. In the coldest months they become much less active and spend most of their time in their burrows.

Both males and females defend territories around their burrows. A threatened male inflates his body, raises his crest and darkens his skin, and rival males may fight and bite.

Reproduction and life cycle

Tuatara breed more slowly than any other reptile. They take 10 to 20 years to mature, and females lay eggs only every two to five years, often about every four. Mating takes place in late summer, around January to March. A courting male darkens, raises his crest and walks stiffly in circles around the female. Males have no penis: as in most birds, sperm passes when the two cloacas are pressed together.

A female needs one to three years to supply her eggs with yolk, and up to seven months to form the shells. In spring, around October to December, she lays about 5 to 18 soft, parchment-shelled eggs in a shallow nest burrow, and some females guard the nest for up to about ten days against other females looking for a nest site. The eggs take roughly 12 to 15 months to hatch, with development pausing in winter, one of the longest incubation periods of any reptile.

As in many reptiles, the temperature of the nest decides the sex of the young. Warmer eggs produce more males and cooler eggs more females: at about 21 °C (70 °F) the sexes are roughly equal, while at 22 °C (72 °F) about 80% of hatchlings are male. This has raised concern that a warming climate could skew some populations toward males.

Hatchlings are independent from the start. They grow extremely slowly and keep growing until they are about 35 years old.

How long do tuataras live?

Tuatara are among the longest-lived reptiles. Their average lifespan is often given as about 60 years, wild tuatara are known to be still breeding at around that age, and some individuals pass 100. The most famous is Henry, a male at the Southland Museum and Art Gallery in Invercargill, who hatched on Takapourewa sometime between the 1890s and 1910s. In 2009, at an age widely reported as about 111, he fathered 11 hatchlings with a female named Mildred.

Exact ages are hard to measure, because the growth rings in tuatara bones stop forming after a few decades. What is documented and what is estimated is explained in How long do tuataras live?, and other record-holders appear in the longest-living animals.

Threats and conservation status

The IUCN Red List classifies the tuatara as Least Concern (assessed in 2019), reflecting a total population usually estimated at roughly 60,000–100,000 animals, most of them on a few large, protected islands. New Zealand’s own threat classification lists it as At Risk – Relict, meaning it now survives in only a small part of its former range. Tuatara have been protected by law since 1895, are absolutely protected under the Wildlife Act 1953 and are listed on CITES Appendix I, which bans commercial international trade.

The main threat is introduced mammals. Rats, especially kiore, eat eggs and hatchlings and compete for insect food; on rat-infested islands adult tuatara hung on for decades but stopped producing young. Other risks include fire, poaching, low genetic diversity in small island populations and climate change. Conservation has been a real success: rats have been eradicated from many islands, eggs have been incubated and juveniles raised in captivity, and between 1995 and 2020 tuatara were moved to 14 islands and 5 mainland sanctuaries.

Myths and facts

Myth: The tuatara is a dinosaur. It is sometimes nicknamed a “living dinosaur”, but it is not one. Tuatara belong to a separate reptile line that lived alongside the dinosaurs and is more closely related to lizards and snakes.

Myth: Tuatara have not changed for 200 million years. “Living fossil” is a popular label, but many biologists avoid it. Early relatives of the tuatara looked similar, yet there is no continuous fossil record showing an unchanged species, and the living tuatara has its own specializations. The same debate surrounds the coelacanth.

Myth: Tuatara have no real teeth, just a jagged jaw. Microscope studies show they have true teeth, with enamel and dentine, firmly fused to the jawbone.

Fact: Tuatara can drop their tails. Like many lizards, a tuatara can shed part of its tail when grabbed by a predator and slowly regrow it.

Tuatara and people

For Māori, tuatara are taonga, treasured species, and are regarded as kaitiaki, guardians of knowledge. In tradition they are messengers of Whiro, the god of death and disaster, and they mark the boundaries of tapu, places that are sacred or restricted. Iwi (tribes) connected to tuatara islands are partners in their conservation, and the tuatara genome, published in 2020, was sequenced in partnership with the Ngātiwai iwi.

The tuatara appeared on New Zealand’s five-cent coin until the coin was withdrawn in 2006. Today visitors can see tuatara in fenced sanctuaries such as Zealandia, on open sanctuary islands such as Tiritiri Matangi, and in New Zealand zoos and breeding centers that raise young for release. In 2016 Chester Zoo in England announced the first captive breeding of tuatara outside New Zealand.