How Long Do Tuataras Live? Slow Growth and Long Lives

Average lifespan and maximum age

New Zealand’s Department of Conservation gives the average lifespan of a tuatara as about 60 years and says they can live to 100. Wild tuatara are known to be still breeding at around 60, so this is not old age for the species. Several captive tuatara have lived past a century.

Some experts have suggested that captive tuatara could live as long as 200 years, but that figure is speculation rather than a documented age. It is safest to say that tuatara commonly reach 60 years or more and that individuals older than 100 are known.

Henry: a father past 100

The most famous old tuatara is Henry, a male who hatched on Takapourewa (Stephens Island) sometime between the 1890s and 1910s. He arrived at the Southland Museum and Art Gallery in Invercargill in 1970. Early attempts to breed him failed: in the 1980s he bit off the tail of a female named Mildred, and he was so aggressive toward other tuatara that he was kept alone.

In 2009, at an age widely reported as about 111, Henry became a father for the first time. Eleven of the eggs laid by Mildred, herself thought to be 70 to 80 years old, hatched, and the story made headlines around the world. In 2024 Henry and other tuatara moved to a new enclosure in Invercargill’s Queens Park while the museum is rebuilt.

Henry’s exact age is unknown, as with almost all old tuatara, but there is no doubt that he has lived well over a century.

Slow growth and late maturity

Tuatara probably have the slowest growth rate of any reptile. Hatchlings are small enough to sit in the palm of a hand, and it takes decades for them to reach full size: they keep growing until they are about 35 years old, when males reach about 61 cm (24 in) and up to 1 kg (2.2 lb) or a little more, and females about 45 cm (18 in) and 0.5 kg (1.1 lb).

Breeding is just as slow. Tuatara usually mature at 10 to 20 years old. A female then needs one to three years to supply her eggs with yolk and up to seven months more to form the shells, so she lays only every two to five years, the slowest rate of any reptile. The eggs take about 12–15 months to hatch. A long life is what allows tuatara to produce enough young to replace themselves.

Why do tuatara live so long?

There is no single explanation, but several factors work together:

• A cool, slow body. Tuatara are active at temperatures as low as about 5 °C (41 °F), and their preferred body temperature of 16–21 °C (61–70 °F) is the lowest of any reptile. A cool body runs a slow metabolism, and across the animal kingdom slow-living species tend to age slowly.
• Few enemies as adults. On rat-free islands an adult tuatara has few natural predators, so there has been little pressure in its evolution to breed quickly before something kills it.
• A slow life history. Animals that mature late and breed rarely, as tuatara do, generally have long lifespans, because each adult must survive many years to raise enough young.
• Possible genetic factors. The tuatara genome contains genes linked to protection against cell damage, and some researchers have suggested they may contribute to its longevity. This is an idea under study, not a proven explanation.

Like other reptiles, tuatara depend on outside heat to warm their bodies; how this works is explained in Are reptiles cold-blooded?

How do scientists work out a tuatara’s age?

Measuring the age of an old wild tuatara is surprisingly hard. Like tree rings, bones lay down growth rings, and scientists can count them under a microscope. In tuatara, though, the rings in the toe bones stop forming at about 12–14 years, and those in the thigh bone at about 25–35 years. After that the bones no longer record the years.

For older animals, researchers rely on long-term studies in which individual tuatara are marked and recaptured over many years, on records of captive animals of known history, and on clues such as tooth wear, since tuatara never replace their teeth. That is why the ages of the oldest tuatara, including Henry, are always given as estimates.

How tuatara compare with other long-lived reptiles

Among reptiles, only the giant tortoises are known to live clearly longer. Jonathan, a Seychelles giant tortoise on St Helena, is thought to have hatched around 1832, which would make him roughly 190 or more; see Who is Jonathan the tortoise? Tuatara are often ranked just behind the tortoises, ahead of crocodilians and nearly all lizards and snakes.

For a wider view of which animals live longest, from tortoises and whales to sharks and clams, see the longest-living animals.