status: Endangered, ESA
range: New Zealand
Description and biology
The tuatara (pronounced too-a-TAR-a) is a lizardlike reptile. It is olive green and speckled with yellow. It has a medium-sized head and a strong tail. The tuatara's feet and hands each have five clawed digits (toelike projections). A crest of soft spines stretches along its back to the base of its tail. An average female tuatara measures 20 inches (51 centimeters) long and weighs about 1 pound (0.45 kilogram). An average male measures 24 inches (61 centimeters) in length and weighs about 2.6 pounds (1.2 kilograms).
The tuatara has certain physical characteristics that separate it from lizards. Among other things, it has extra holes in its skull and bony projections on its ribs. Males of the species lack a copulating (breeding) organ. It has a single row of teeth in its lower jaw and a double row in its upper jaw. When the tuatara's mouth is closed, its bottom row of teeth fit neatly between its upper two rows. None of these teeth are replaced
when worn out or damaged. This reptile also has a third eye—called a pineal eye—on the top of its head. The eye contains a simplistic lens and retina and is connected to the brain by a nerve. Since this eye is covered by opaque scales, not much light gets through. Some biologists (people who study living organisms) believe the eye may function as a light sensor, determining how much time the tuatara spends basking in sunlight.
The tuatara is mainly nocturnal (active at night). It feeds on worms, snails, beetles, crickets, birds' eggs, small lizards, and frogs. During the day, when not basking in the sun, the tuatara spends time in burrows built as nests by shearwaters and petrels (both sea birds).
Since males do not have copulating organs, tuataras breed like birds. When mating, a male and female bring their cloacae into contact. A cloaca (pronounced klow-AH-ka) is a cavity in the body of birds, reptiles, amphibians, and most fishes that has an opening to the outside through which sperm and body wastes such as feces pass. Once having mated, a female tuatara lays a clutch of 6 to 10 eggs in a burrow or tunnel sometime between October and December. The female abandons the eggs after covering them with soil and the eggs hatch 13 to 15 months later. Tuataras can live up to 100 years.
Habitat and current distribution
The tuatara is found on about 30 islands around New Zealand. Biologists estimate that the current tuatara population is between 60,000 and 100,000. More than half of all tuataras exist on Stephens Island.
History and conservation measures
Tuataras are the most ancient of all living reptiles. They are the last surviving members of a family of reptiles that stretches back to the early Mesozoic Era, about 200,000,000 years ago. During the age of reptiles, tuataras lived alongside dinosaurs. With the extinction of the dinosaurs 65,000,000 years ago, the age of mammals began and the tuatara soon disappeared from everywhere on Earth except New Zealand.
Humans first came to the New Zealand islands from nearby Polynesian islands sometime between 1,000 and 2,000 years ago. They brought with them the kiore, or Polynesian rat. The kiore quickly became a predator of tuatara eggs and young. As more humans came to the New Zealand islands, bringing with them predators such as pigs and cats, the tuatara suffered. By the end of the nineteenth century, the reptile had become extinct on the main islands of New Zealand.
Efforts are currently underway to remove rats from tuatara island habitats. On the island of Tiritiri Matangi, all rats have now been eliminated. The island now teems with rich plant life, insects, lizards, forest birds, and tuataras. All islands on which tuataras are found are designated either wildlife sanctuaries or flora and fauna reserves. Both of these designations limit the number of humans who can visit these islands.
Tuataras (class Rhynchocephalia) superficially resemble lizards (class Reptilia), but the two known species are actually members of the smallest terrestrial vertebrate class on Earth, the Rhynchocephalia, a unique and ancient evolutionary lineage whose fossils (from Asia, Europe, North and South America, and Africa) first appeared in the early Triassic more than 220 million years ago. Today, Tuataras are found only on about thirty islands off the coast of New Zealand; their ancestors on other continents became extinct around 65 million years ago.
Male Tuataras lack a penis or other copulatory organ (unlike mammals, turtles, reptiles, crocodilians, and birds), possess a skull with two pairs of arches (like crocodilians), exhibit teeth on the palatine bones of the jaw (unlike lizards), and have teeth that are set squarely on the jawbone (with limited ability for replacement when lost, unlike the class Reptilia); old individuals may have teeth worn entirely away. Tuataras lay shelled eggs on land (unlike the class Amphibia), and the eggs may take as long as fifteen months to hatch. Tuataras live in burrows, emerging mostly at night but sometimes during the day to bask in the sun.
Tuataras are long-lived, apparently reaching over one hundred years of age. Males are larger (up to 61 centimeters [2 feet] in length and 1 kilogram [2.2 pounds] in weight) than females (45 centimeters [1.4 feet], .15 kilograms [.33 pounds]). They are insectivorous (depending on insects for food), but will opportunistically prey on small vertebrates. Tuatara is a Maori word meaning "peaks or spines on the back," in reference to the conspicuous middorsal crest on the back and tail of males and, to a lesser extent, females. Access to much of the remote island habitat of this animal is difficult, providing it with protection from human disturbance; historically, on those islands where access was less daunting, humans arrived, and the tuataras became extinct.
see also Amphibian; Crocodilians; Extinction; Reptile
Joseph T. Collins
Pough, F. Harvey, et al. Herpetology. Upper Saddle River, NJ: Prentice Hall, 1998.
Robb, Joan. New Zealand Amphibians and Reptiles. Auckland, Australia: Collins, 1986.