TUATARA: Sphenodontidae

PHYSICAL CHARACTERISTICS

At a glance, each of the two species of tuatara could be mistaken for a lizard. A closer look, however, reveals how different they really are. One difference is in their teeth. Tuataras have not one, but two rows of teeth lying side by side in the upper jaw. When the mouth closes, the single row of teeth in the lower jaw fits between the two upper rows. Tuataras have ears as lizards do, but lizards have an ear opening on each side of the head and tuataras do not. Baby tuataras have another unusual feature. They have a pale patch on the top of the head, which some people have called a "third eye." The patch becomes covered with scales as the animal grows up. Scientists are unsure of the patch's purpose but believe it may allow the reptile to see light from the sun. Such information about the sun's location may help the animal find its way.

A tuatara has a large head on a sturdy body that ends in a thick tail. Its skin is wrinkly and covered with noticeable beady scales. A white crest runs along the back of the head and down the middle of the back. The tail also has a row of toothy spines down its center. Males are larger and heavier than females, and they also have larger crests on the head and back. The biggest of the two species, the northern tuatara, can grow to more than 24 inches (61 centimeters) long from head to tail and weigh at least 2 pounds (1 kilogram). The smaller females of the species usually reach 16 inches (40.6 centimeters) and 1 pound (0.5 kilograms) at most. The other species, known as Brother Islands tuatara, is slightly smaller.

The Brother Islands tuatara is often a bit greener in color than the greenish brown northern tuatara, but both are sometimes reddish to almost black in color. The two species have white and black blotches and spots, but the Brother Islands tuatara usually has more white spots. Young tuataras of both species are commonly light grayish brown with light V-shaped patterns running along the back and dark markings by the eyes.

GEOGRAPHIC RANGE

Tuataras have a small range, living on about 30 tiny and hard-to-reach islands off New Zealand's shore.

HABITAT

Although neither species is widespread, the northern tuataras make their homes over a bigger area than the Brother Islands tuataras. The northern tuataras live on 26 islands off northeastern North Island and on four islands of Cook Strait off the northern coast of South Island. The Brother Islands tuatara lives only on North Brother Island in Cook Strait. Both species are burrowers and live in shady forests where the trees grow thick enough to block the sun almost completely from reaching the ground.

DIET

Usually active at night, the tuataras often hunt by ambush, which means that they sit still and wait for a prey animal to come to them. They also forage (FOR-ej), which means that they wander about looking for food. They use their sticky fat tongues to catch and eat mainly non-flying grasshoppers, beetles, and other crawling invertebrates (in-VER-teh-brehts), which are animals without backbones. The unusual arrangement of their teeth is not only excellent for crushing invertebrates but is also well-suited to the occasional meal of a seabird, lizard, or perhaps a smaller tuatara. The younger tuataras are more likely than the adults to hunt during the daytime. This practice may help them avoid being eaten by adult tuataras.

BEHAVIOR AND REPRODUCTION

Tuataras are most active at night, which is when they do the majority of their hunting. During the daytime, each one lives alone in its underground burrow, occasionally coming to the burrow entrance to sunbathe, or bask, and warm their bodies. Tuataras live on very small islands that may become rather crowded, sometimes with tuatara burrows less than 3 feet (0.9 meters) apart. In some cases, 810 tuataras may share a single acre of land (2,000 per hectare). They get along quite well, but males will fight one another for small territories, where they hope to attract females for mating. The battles begin with two males lining up next to each other, with each facing in the opposite direction. They then puff up the throat, stiffen the crest spines on the back so they stand on end, open wide the mouth, and snap the jaws shut tight. Usually this display is enough for one of the two males to surrender and leave the area. Occasionally, however, neither one retreats, and the two males engage in biting matches.

Females mate once every two to five years, but males mate every year. Males set up their territories in summer and fall and begin doing what is called a "proud walk" to catch a female's eye. Doing some of the displays he does when battling males, he tries to attract a female by slowly strutting around her while stiffening his back crest and puffing up his throat. If she is interested, she stays. If not, she simply walks away. After mating, a female must wait until the following spring to lay her eggs. Most lay four to 13 eggs, but the larger northern tuataras from Cook Strait often lay eight to 15. Each female makes a hole that may be very shallow or up to 20 inches (50 centimeters) deep, lays her eggs, and covers them loosely with dirt. The eggs do not hatch until 12 to 15 months later. As in many other reptiles, the temperature of the nest controls whether the eggs hatch into males or females. In the case of the Brother Islands tuatara, warmer nests produce mostly males, and cooler ones produce mostly females. Tuataras cannot mate until they are up to 13 years old. They live to be at least 60 and possibly much longer.

A VERY OLD REPTILE

The tuatara is the only descendant of an ancient group of reptiles that were common in the late Triassic and Jurassic periods about 180 to 220 million years ago. At that time, they were spread out over Europe, Africa, and North America. They started to disappear during the dinosaurs' reign, and almost all of them were completely gone by the early Cretaceous Period, which followed the Jurassic. A tiny group, however, survived on a piece of land that broke off the mainland and eventually formed the islands of New Zealand. This group of animals, called a lineage (LIN-ee-ej) because it connects species through time to their ancestors, gave rise to the two current-day tuatara species.

TUATARAS AND PEOPLE

The people of New Zealand hold the tuatara in high regard and consider them to be living treasures. Tuataras have also caught the eye of the science community. In the 1800s, for example, so many scientific institutions wanted their own tuataras to study that the local government in 1895 was forced to protect the reptile before its population dropped too low.

CONSERVATION STATUS

The World Conservation Union (IUCN) considers the Brother Islands tuatara to be Vulnerable, which means that it faces a high risk of extinction in the wild. The U.S. Fish and Wildlife Service lists both species as Endangered or in danger of extinction throughout all or a significant portion of their range. One of the greatest threats to the tuataras comes from introduced species, especially rats, which attack and kill the reptiles. Several programs are under way to remove the rats and to prevent any other predators from reaching the islands; these efforts are helping the tuataras to make a comeback. In addition, other programs are helping to return tuataras to those places where they once lived but had disappeared.

NORTHERN TUATARA (Sphenodon punctatus): SPECIES ACCOUNT

Physical characteristics: The northern tuatara is a beady-skinned, lizard-looking animal with a crest on the back of its head and on its back. Its color may be gray, greenish gray, red, or black. Males can reach more than 24 inches (61 centimeters) long and 2 pounds (1 kilogram). Females are smaller, usually growing to no more than 16 inches (40.6 centimeters) and 1 pound (0.5 kilograms).

Geographic range: The northern tuatara lives on about 30 islands off New Zealand's coast.

Habitat: Northern tuataras spend much of their lives in or around their underground burrows.

Diet: Their diet is about 75 percent invertebrates, especially beetles and grasshoppers. They occasionally eat lizards, small birds, and other vertebrates (VER-teh-brehts), which are animals with backbones.

Behavior and reproduction: During the day, northern tuataras remain in their burrows, occasionally coming to the entrance to bask in the sun. They do most of their hunting at night. Although they get along quite well, considering that they may sometimes live less than 3 feet apart, the males do fight, especially during the breeding season. Males mate every year, but females mate only once every 2 to 5 years.

Northern Tuataras and people: Local people respect this reptile. The New Zealand government is very strict in its protection of the tuataras, even limiting travel to the islands where the reptiles live.

Conservation status: The World Conservation Union (IUCN) does not consider this species to be at risk, but the U.S. Fish and Wildlife Service considers it to be Endangered or in danger of extinction throughout all or a significant portion of its range. Efforts are under way to remove introduced predators, especially rats, from the tuatara's islands. ∎

FOR MORE INFORMATION

Books:

Tesar, Jenny. What on Earth is a Tuatara? Woodbridge, CT: Blackbirch Press, 1994.

Periodicals:

"Quick Bits: Tuatara." Ranger Rick. August 1999, vol. 33, page 12.

"Tuataras 'The Living Fossil' Explained." Monkeyshines on Health & Science. Spring 1998, page 14.

Web sites:

Musico, B. "Sphenodon punctatus." Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Sphenodon_punctatus.html (accessed on December 20, 2004).

"The Tuatara." Kiwi Conservation Club. http://www.kcc.org.nz/animals/tuatara.asp (accessed on December 20, 2004).

"Tuatara." San Diego Zoo. http://www.sandiegozoo.org/animalbytes/t-tuatara.html (accessed on December 20, 2004).

"What Can You Tell Me About Tuatara?" Museum of New Zealand Te Papa Tongarewa. http://www.tepapa.govt.nz/TePapa/English/CollectionsAndResearch/FAQs/FAQs_NaturalEnvironment.htm#tuatara (accessed on December 20, 2004).