Tuatara are New Zealand’s largest reptile. Adult males measure up to about:
- 0.5 metres in length, and
- weigh up to 1.5 kg when fully grown.
The male has a distinctive crest of spines running along the neck and down the back. He can erect these spines to attract females or when fighting with other males.
The colour of tuatara ranges from olive green to brown to orange-red. They can also change colour over their lifetime. They shed their skin once per year.
What they eat and like
Their diet consists primarily of invertebrates such as:
- millipedes, and
The remainder of what they eat is made up of lizards, seabird eggs and chicks. They even, on occasion, eat their own young.
Unusual for reptiles, tuatara can be active in cool weather. Experimentally, it has been found that they don't thrive in constant temperatures over 25 C°. Even so, in the wild they will seek out sunny places to bask. When temperatures are low they will remain in their burrows.
Lifespan – around 60 years
Tuatara have one of the slowest growth rates of any reptile. They keep growing until they are about 35 years old. A tuatara’s average life span is about 60 years but they probably live up to 100 years.
Where they are
Tuatara once lived throughout mainland New Zealand but naturally wild populations are now only found on islands off the northern east coast of the North Island and some islands in the Marlborough Sounds.
Significantly, these islands are free of rodents and other introduced mammalian predators that prey on eggs and young of tuatara as well as compete for their invertebrate food.
The islands are usually occupied by colonies of breeding seabirds. These seabirds contribute to soil fertility and thus the richness of invertebrate and lizard fauna, both of which are tuatara prey.
Advances in the captive incubation and raising of tuatara have allowed the species to be translocated to a further four islands that they presumably inhabited in the past. The ability to eradicate rodents from islands has also enhanced these efforts.
Only surviving member of the order Sphenodontia
Tuatara are the only surviving members of the order Sphenodontia. This order was well represented by many species during the age of the dinosaurs, some 200 million years ago. All species except the tuatara declined and eventually became extinct about 60 million years ago.
Because of this tuatara are of huge international interest to biologists. They are recognised internationally and within New Zealand as species in need of active conservation management.
The tuatara is a single species Sphenodon punctatus. A second species Sphenodon guntheri was recognised in 1989 but discontinued in 2009 when research concluded tuatara is best described as one species.
Find out more facts
Rats are considered the most serious threat to the survival of tuatara. This is because they’re:
- easily transported as stowaways on boats, and
- usually the first alien animals to arrive unnoticed in new places.
Islands with rats have few nocturnal invertebrates or reptiles. Here, rats rely on seeds, fruits, and other plant material for food because there is little else to eat.
There are three kinds of rats in New Zealand.
Kiore are small rats weighing up to 80g and have been in New Zealand for at least 1000 years. Adult tuatara can co-exist with kiore but tuatara eventually die out where kiore are present.
Kiore would have preyed on eggs and small hatchlings. The slow breeding rate of tuatara means they cannot compensate for such predation pressure.
There were probably few if any, tuatara left on the North and South Islands by the time European settlers arrived in New Zealand.
Norway rats are the largest and weigh up to 450g. Ship rats weigh up to 200g. These two species arrived in New Zealand with European visitors and settlers.
These rats eat and destroy whatever is available, and become prolific breeders when food is plentiful.
Mice are less devastating compared to rats. But they damage natural communities by eating seeds and small insects that native reptiles and birds normally eat and also kill small lizards
Because tuatara only survive on islands, they’re very vulnerable to changes in the islands’ habitat. For example, fires on an island and trampling from illegal landing by people.
In 1895 tuatara were protected by law, one of New Zealand’s first native species to be so protected. Before then, hundreds of specimens were shipped overseas for museums and private collections. Poaching is still a problem, although this has diminished because of tuatara’s legal protection and remote habitat locations.
Low genetic diversity
Low genetic diversity is a significant threat to survival of many tuatara populations. While a few populations are large and healthy, some populations on very small islands have naturally low genetic diversity because the islands are too small to carry a large healthy population. Many other populations were reduced to just a handful of old tuatara by rats before the rats were eradicated. In these latter cases, the populations started to recover but with permanently decreased genetic diversity.
That makes the whole population susceptible to a disease or global warming as it has not evolved with enough variability so that some of the population can adapt to those new circumstances. A further complication is that each island tuatara population is isolated from others so no ‘genetic mixing’ can naturally take place.
The continued conservation of tuatara relies largely on public goodwill in preventing rodents establishing on their island refuges.
On most islands, this means complying with the 'no-landing' rule. But on others you must make sure no pests go ashore with you by checking your gear. For example: