Wildlife Guide · New Zealand — around 30 offshore islands and fenced mainland sanctuaries
Tuatara
Sphenodon punctatus (Gray, 1842) — family Sphenodontidae
Not a lizard. The last survivor of a reptile order that has been separate for 250 million years.
Image: AI-generated educational wildlife portrait — World Animal Rescue Network · AI visualisation, not a photograph
In brief
The tuatara is a New Zealand reptile that is the only surviving member of the order Rhynchocephalia, a lineage separate from lizards and snakes for around 250 million years; it lives over 100 years, thrives at 16–21°C, and survives only on predator-free islands.
By the WARN Research & Conservation TeamChecked against IUCN Red List & CITES sourcesLast updated
The tuatara looks like a lizard and is not one. It is the only surviving member of the order Rhynchocephalia, a lineage that separated from all other reptiles roughly 250 million years ago — before the first dinosaurs. Every lizard and snake alive today, from a gecko to a python, is more closely related to every other lizard and snake than any of them is to a tuatara. It is also biologically odd in ways that follow from that isolation. It has a functioning light-sensitive third eye on top of its head in juveniles, two rows of upper teeth that a single lower row bites between, the lowest preferred body temperature of any reptile, and a lifespan that can pass a century. It survives on around 30 New Zealand offshore islands, and essentially nowhere that has rats.
~250 million yr
Since the tuatara's order separated from lizards and snakes
1
Surviving species of an order that once spanned the globe
16–21°C
Preferred body temperature — the lowest of any reptile
100+ yr
Lifespan, with credible estimates well beyond
Figures sourced from IUCN Red List — Sphenodon punctatus, New Zealand Department of Conservation — Tuatara .
Tuatara: Quick Facts
| Length | Up to about 80 cm including tail |
|---|---|
| Lineage age | Around 250 million years separate from lizards and snakes |
| Preferred body temperature | 16–21°C — the lowest of any reptile |
| Lifespan | Over 100 years |
| Incubation | 12–15 months, one of the longest of any reptile |
| Sex determination | Temperature-dependent — warmer nests produce males |
Scientific Classification
| Kingdom | Animalia |
|---|---|
| Phylum | Chordata |
| Class | Reptilia |
| Order | Rhynchocephalia |
| Family | Sphenodontidae |
| Genus | Sphenodon |
| Species | Sphenodon punctatus |
Conservation Status
- IUCN Status
- Least Concern
- Population
- Roughly 60,000–100,000 across around 30 islands and sanctuaries
- Trend
- Stable under active management
- Assessed
- 2019
- CITES
- Appendix I
Stable only because of sustained invasive-predator control. Warming at nest sites is the emerging threat, since temperature-dependent sex determination would skew populations male.
Did you know?
Henry, a tuatara at Southland Museum in Invercargill, became a father at an estimated 111 years old — after roughly four decades of showing no interest in females, which staff eventually traced to a tumour.
Key Facts: Tuatara
- Tuatara are not lizards. They are the only living members of Rhynchocephalia, an order that diverged from the lizard and snake lineage around 250 million years ago.
- They have a parietal or third eye on top of the head — complete with lens, retina and nerve connection — visible in hatchlings and covered by scales as they mature.
- The teeth are fused to the jaw rather than set in sockets, arranged as two upper rows and one lower row that shears between them.
- They prefer body temperatures of 16 to 21°C, lower than any other reptile, and remain active at temperatures where most reptiles cannot function.
- Tuatara live over 100 years and mature very slowly, breeding for the first time at around 10 to 20 years and laying eggs only every two to five years.
- Sex is determined by incubation temperature, so warming nest sites skew clutches male — the opposite direction to most reptiles.
- Introduced Pacific rats eliminated them from the New Zealand mainland. They survive on around 30 offshore islands and in fenced sanctuaries.
Why the tuatara is not a lizard
The resemblance is superficial. Tuatara belong to Rhynchocephalia, a reptile order that was widespread and diverse in the Mesozoic and is now reduced to a single genus on a handful of islands. The split from Squamata — lizards and snakes — dates to roughly 250 million years ago, in the Triassic, before dinosaurs became dominant. The anatomical differences are substantial. Tuatara retain a complete diapsid skull with two temporal openings and a solid bony arch that lizards have lost, giving the skull a rigidity lizards do not have. Their teeth are acrodont, fused directly to the jawbone rather than sitting in sockets, and are not replaced when worn — an old tuatara has blunt teeth and switches to softer prey. They have no external ear opening and, uniquely among reptiles, no copulatory organ; mating is by cloacal contact, as in most birds.
The third eye
A hatchling tuatara has a visible parietal eye on top of its head: a small structure with its own lens, retina and nerve connection to the brain, covered by a translucent scale. It is not used to form images. Over the first few months, scales and pigment grow over it and it becomes invisible from outside, though it remains connected internally. Parietal eyes exist in some lizards and frogs too, but the tuatara's is the most fully developed in any living animal. Its function is thought to involve regulating circadian rhythm and seasonal cycles by measuring day length, and possibly thermoregulation — a tuatara that can sense sunlight on the top of its head has information about basking conditions without needing to look up. It is a genuine window onto a sensory arrangement most vertebrate lineages abandoned.
Living slowly, and what that costs
Everything about tuatara biology runs at low speed. They have the lowest metabolic rate of any reptile studied, are active at temperatures where other reptiles are torpid, grow until around 35 years old, and breed for the first time somewhere between 10 and 20. Females lay a clutch only every two to five years, and eggs incubate in the ground for 12 to 15 months — one of the longest incubation periods of any reptile. That pace is well suited to a cool, stable, predator-free island and catastrophically unsuited to anything else. A population that replaces itself this slowly cannot absorb losses. Introduced Pacific rats, brought by early Polynesian settlers, ate eggs and hatchlings faster than tuatara could produce them, and cleared them from mainland New Zealand entirely. It is the kākāpō problem in reptile form.
Conservation and the temperature problem
Tuatara are listed as Least Concern, which reflects a stable total population rather than security. They persist on around 30 offshore islands, several of which have had rats eradicated specifically to allow reintroduction, plus fenced mainland sanctuaries such as Zealandia in Wellington, where tuatara bred in the wild on the mainland in 2009 for the first time in around 200 years. The emerging threat is temperature. Tuatara have temperature-dependent sex determination running in the unusual direction: warmer nests produce males. Sustained warming at nesting sites would push populations toward a male bias and eventually toward reproductive failure. Because the islands are small and fixed, the animals cannot shift range in response. Management options — shading nest sites, translocation to cooler islands — exist, but they require the kind of continuous funded monitoring that a Least Concern listing tends not to attract.
What WARN Does
WARN publishes free, sourced species education. The tuatara is one of the clearest cases of a species that looks secure on paper and is not: a single surviving lineage, on small islands, dependent on continuing invasive-predator control that has to be funded every year without a crisis to prompt it.
If this guide helps you understand wildlife and the pressures it faces, a gift to WARN supports habitat protection and free public education in our partner countries.
Tuatara: Frequently Asked Questions
Is a tuatara a lizard?
Does the tuatara really have a third eye?
How long do tuatara live?
Where do tuatara live?
Are tuatara endangered?
Why do tuatara prefer cold temperatures?
Are tuataras dangerous?
What do tuatara eat?
How big is a tuatara?
Sources & References
Population figures, conservation status and biological facts on this page are drawn from authoritative scientific and intergovernmental sources.
Terms used on this page
Plain-English definitions, from our wildlife and conservation glossary.
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