These are the only living survivors of an order of reptiles that flourished during the Triassic Period. Although it is often called a living fossil, the two surviving species of tuatara have evolved significantly to suit their modern habitat and share few traits with their ancestors.

Description

The word "tuatara" is a Maori word that means "peaks on back," referring to the row of spines running from the head down the middle of the back. Males have much larger spines than females, and they can fan them out during courtship and as a threat display.

Tuataras may be gray, olive, or brick red in color, and their color may change as they age. An adult may be up to 31 inches long and weigh up to 3 pounds, with males being larger than females. Because they have a very slow metabolic rate, tuataras don't stop growing until about 30 years of age. That slow metabolic rate also make them very long-living, with ages of 100 years or more being fairly common.

Although it looks like a big lizard, the tuatara shares very few characteristics with its reptilian cousins. Like many lizards, a tuatara can regrow a lost tail. Unlike most lizards, however, tuataras lack external ears. Unlike any other toothed reptile, a tuatara's teeth are fused to the jaw bone, meaning they will not be replaced if broken off or worn down; this means that a tuatara's diet must get softer as gets older. The tuatara also has a "third eye" on the top of its head. Although that eye has a retina and nerve endings, it does not appear to serve any sensory purpose, and as the animal grows it becomes covered by scales and pigment, becoming almost invisible to the naked eye.

Distribution and Habitat

Tuataras were once found throughout New Zealand and surrounding islands but became extinct on the mainland after it was settled by humans; the dogs and rats that accompanied the humans decimated tuatara nests. Today they are only found on about 30 small, relatively inaccessible islands. Most of those islands are cliff-bound and subject to strong winds, with the majority of vegetation being stunted. The average temperature in the islands ranges from just above freezing to around 70 degrees Fahrenheit. Tuataras can remain active at temperatures down to 45 degrees, the lowest threhold of all reptiles, and will die if exposed to temperatures above 82 degrees.

Diet

Tuataras feed on arthropods, earthworms, snails, bird eggs, small birds, frogs, lizards, and even young tuataras. Since adults do almost all of their hunting at night, youngsters do theirs during the day to avoid becoming an adult's meal. One advantage of having a slow metabolic rate is that a tuatara can go longer between meals than any other reptile.

Reproduction

Tuataras do not reach sexual maturity until 15-20 years of age, the longest maturation period of all reptiles, and a female will only mate once every 3-4 years. Mating takes place from mid-summer to early autumn (January-March), but the eggs are not laid until the following spring or early summer (October-December). When she is ready, the female will bury her 5-18 eggs in a sunny place, after which she leaves them to incubate and hatch on their own. Because embryo development stops during the winter months, it takes 12-15 months for the eggs to hatch. Like some other reptiles, such as alligators, the temperature of the nest where it incubated as an egg determines a tuatara’s gender. It has been found that a difference of just one degree centigrade can change the young in a clutch of eggs from all females to all males.

Other Habits and Behaviors

The tuatara is solitary except at mating, and makes its home in a burrow that may or not be defended. It will willingly share its burrow with another animal, as long as it isn't another tuatara.

Males combat each other by inflating their bodies, elevating their crests, and darkening the skin between the shoulders and neck crest. They also approach females in this manner prior to breeding.

The animal's slow metabolism means it can go for up to an hour without breathing.

Although it is primarily nocturnal, a tuatara will bask at the entrance to its burrow entrance on sunny days.

Conservation Status

Tuataras have been protected by New Zealand law since 1895. Access to most of the islands on which they live is strictly limited, and even zoos must have special permission to take one out of the wild. The exact population of wild tuataras is unknown but is believed to be 50-100,000.

Scientific Classification

phylum Chordata
subphylum Vertebrata
class Reptilia
order Rhynchocephalia
family
genus & species
Sphenodon punctatus (common tuatara)
S. guntheri (Brothers Island tuatara)

SOURCE
Animal Diversity Web animaldiversity.org/accounts/Sphenodon_punctatus/

SEE ALSO
Alligators

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This page was last updated on June 22, 2017.