Tuatara: Sphenodontidae

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.