The tuatara, Sphenodon punctatus, a nocturnal reptile, is one of New Zealand's most unique animals. All other living reptiles are classified into three orders, but the tuatara is the only surviving representative of an otherwise extinct order of “beak-headed” reptiles, the Rhynchocephalia, which lived some 200 million years ago in Asia, Africa, Europe, and North America, and became extinct more than 100 million years ago.
The tuatara closely resembles some lizards in appearance, but, despite the superficial similarity, certain skeletal and anatomical features distinguish the tuatara from the lizards. The tuatara reaches a length of almost 2 ft, and has a lizard-shaped body with a crest of softish spines forming a midrow along the back of the head, and a row of smaller spines along the middle of the back. The spines, the skin folds of the neck, and the total weight and length all reach greater sizes in males than females. Adult males weigh up to 1,000 grams, almost twice the weight reached by females. The animal is usually an olive-green colour but specimens vary from slate grey to almost brick red and all have the background colour broken by numerous small lighter spots. The well-developed pineal organ, or so-called “third eye”, prominent in the young tuatara, is also found in lizards. So far as is known it does not function as a light receptor.
Once the tuatara inhabited the mainland of New Zealand but is now found only on 20 small exposed islands which are covered to some extent by scrub or low coastal forest. One group of islands is in Cook Strait, the others lie off the North Island between North Cape and East Cape. The tuataras make burrows in loose soil or use the burrows of sea birds such as prions, shearwaters, and diving petrels, and may even share burrows with birds incubating eggs or rearing chicks.
Mating is believed to occur in January, and between October and December the females lay from eight to 15 oval eggs in a clutch at the bottom of a shallow excavation about 5 in. deep. The parent abandons the eggs after covering them with earth. Some 15 months later the young cut their way through the flexible parchment-like shell of the egg with the small temporary “egg breaker” at the tip of the snout. The earth-coloured young then butt their way through the soil to the surface where they seek cover in rock crevices, under logs, or in small burrows which they excavate for themselves. Tuataras only become sexually mature after about 20 years of growth, and continue to grow slowly all their lives. Very large tuataras could be more than a century old, for the tuatara has one of the slowest rates of growth of any reptile.
Young tuataras feed readily on small ground animals, such as earthworms and small insects. Adults forage for wetas (wingless crickets), beetles, snails, and, occasionally, the eggs and young of petrels. As most of the islands lack streams or pools, tuataras probably get most of their water from their food or dew. Tuataras are active at night, remaining active in temperatures as low as 7°c and they can tolerate high temperatures for brief periods. W. H. Dawbin (1962) gives a detailed account of the life history and habits of the tuatara based on extensive field observations.
The New Zealand Government rigidly protects tuataras to ensure the continued existence of this species, a living relic of an ancient world.
by Richard Essex Barwick, M.SC.(N.Z.), Lecturer, Zoology Department, School of General Studies, Australian National University, Canberra, A.C.T.
- Reptiles, Bellairs, A. d'A. (1957)
- Tuatara, Vol. 2 (1949), “The Tuatara”, Dawbin, W. H.
- Endeavour, Vol. XXI (1962), “The Tuatara in its natural habitat”, Dawbin, W. H.
- Bulletin of the Auckland Zoological Society, No. 2 (1935). “The Tuatara (Sphenodon punctatus),” Falla, R. A.
- Kukenthal and Krumbrac Handbuch der Zoologie, 7 (1931), “Rhynchocephalia”, Von Wettstein, O. (Review of Tuatara technical literature).