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 Adult tuatara are about 50-80cm long and weigh between 400 -500g. However adult males are longer and heavier than females and can grow to 600cm long and weigh up to 1kg. The Brothers Island tuatara have brighter olive-yellow colouring than other tuatara which are more drab in colour. Tuataras are not lizards and one of the features that distinguish them from lizards are their teeth - they have a single row of serration like teeth on the lower jaw which fits between two upper rows of teeth on the upper jaw and the palate. The teeth move forward like shears when the mouth is closed and the grip is so strong the jaws cannot be prised open. Male tuataras also lack a copulatory organ.
One of the mysteries of the tuatara is its ‘third eye’ or pineal or parietal eye located in the middle of the forehead. Although it has a small lens and retina, it is covered with opaque scales and scientists believe it may be used as a light sensor rather than for actually forming images.
The tuataras, Sphenodon punctatus and Sphenodon guntheri, are the only surviving members of the order Sphenodontida, a lineage that stretches back at least 225 million years to the Mesozoic Age - the beginning of the ‘Age of the Reptiles’. All other members of the order (and family) shared the earth with dinosaurs and are known only from fossils.
Tuataras may become sexually mature when they are about 10 or more years old. Males establish territories and begin courtship displays in January or February - he puffs out his cheeks and holds his head up with the crest fully erect. Rival males will fight each other and often suffer serious injuries. After mating the eggs take another seven to eight months to develop within the female and are finally laid in November in nests in open sunny areas. They incubate for another 11-16 months to finally hatch in summer. The eggs absorb moisture from the ground and swell. Baby tuataras use their egg tooth - a sharp pointed spike at the end of the snout - to break the shell and emerge over a few hours.
Tuatara's live for at least 60-70 years but it is possible tuataras can live for as long as 100 or more years. There is no accurate way of aging tuataras which have stopped growing.
Endemic to New Zealand and now found only on offshore islands such as Stephens Island, the Mercury Islands group, Hens and Chickens and Poor Knights Islands. The Brothers Island tuatara are now classified as a separate species Sphenodon guntheri.
Tuatara choose to live in burrows in native forest, but also favour abandoned sheep pasture where possible nesting sites may be more numerous. Tuatara often share burrows with seabirds such as petrels and shearwaters.
Insects, spiders, earthworms, snails and small lizards. They will also kill and eat small seabirds and their eggs as well as juvenile tuataras.
Tuatara are mainly nocturnal and remain in their burrows during the day and prowl at night, when the temperature drops sharply and cold gusts of wind sweep over the islands. These animals are active at lower temperatures than other reptiles, and their body temperatures tends to be lower than that of their surroundings. Body temperatures ranging from 6.2-13.3 °C have been reported in nature. The preferred temperature seems to be about 12 °C. They will often come out during the day to bask in sun just outside their burrows. Although tuataras are do not actually hibernate during winter their metabolism slows down considerably and they can survive for up to six months without feeding over winter. Although most of their movements are slow like other reptiles, when hunting prey or escaping from danger tuatara can move extremely fast.
Until about a thousand years ago, tuatara existed throughout the North and South Islands. Since then fires, land clearing and predation by humans, dogs, cats, rats and other introduced mammals have exterminated tuatara from the lands they occupied for nearly 80 million years. They are now found only on about 30 remote offshore islands from the Brothers Islands in the south to the Poor Knights Islands in the north and are completely protected by law. The largest population is found on Stephens Island in the Cook Strait, where there are at least 30,000 tuatara. Of the other rat-free islands only seven are larger than ten hectares and accidental introduction of Norway or ship rats is a constant threat to all tuatara populations.
Apart from being a unique ancient species that is a survivor from an age when dinosaurs roamed the earth, tuatara are also special to New Zealand. This is the only place on earth that they are (and have ever been) found and they have adapted not only to the land but also to the arrival of humans and continue to survive by finding refuge on a few coastal islands. They deserve our respect and our commitment to ensuring their future here on earth.
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