Tuatara at the Karori Wildlife Sanctuary

Adult tuataras are terrestrial and nocturnal reptiles, though they will often bask in the sun to warm their bodies. Hatchlings hide under logs and stones, and are diurnal, likely because adults are cannibalistic. Tuataras survive in temperatures much lower than those tolerated by most reptiles, and hibernate during winter. They can maintain normal activities at temperatures as low as 7° C, while temperatures over 28° C are generally fatal. The optimal body temperature for the tuatara is from 16 to 21° C, the lowest of any reptile.[10] The body temperature of tuatara is lower than that of other reptiles ranging from 5.2–11.2° C over a day, whereas most reptiles have body temperatures around 20° C.[11] The low body temperature results in a slower metabolism.

Burrowing seabirds such as petrels, prions and shearwaters share the tuataras' island habitat during the bird's nesting season. The tuataras use the bird's burrows for shelter when available, or dig their own. The seabirds' guano helps to maintain invertebrate populations that tuataras predominantly prey on; including beetles, crickets and spiders. Their diet also consists of frogs, lizards and bird's eggs and chicks. Seabirds may provide beneficial fatty acids.

Tuatara juvenile Tuatara juvenile

Tuataras reproduce very slowly; taking ten years to reach sexual maturity. Mating occurs in midsummer; females mate and lay eggs once every four years. During courtship, a male makes his skin darker, raises his crests and parades toward the female. He circles himself around the female while slowly walking with stiffened legs. The female will either submit, and allow the male to mount her, or retreat to her burrow.  Males do not have a penis; they reproduce by the male lifting the tail of the female and placing his vent over hers. The sperm is then transferred into the female.

Tuatara eggs have a soft, parchment-like shell. It takes the females between one and three years to provide eggs with yolk, and up to seven months to form the shell. It then takes between 12 and 15 months from copulation to hatching. This means reproduction occurs at 2 to 5 year intervals, the slowest in any reptile. The sex of a hatchling depends on the temperature of the egg, with warmer eggs tending to produce male tuataras, and cooler eggs producing females. Eggs incubated at 21° C have an equal chance of being male or female. However, at 22° C, 80% are likely to be males, and at 20° C, 80% are likely to be females; at 18° C all hatchlings will be females. There is some evidence that sex determination in tuataras is determined by both genetic and environmental factors.

Tuataras probably have the slowest growth rates of any reptile, continuing to grow larger for the first 35 years of their lives. The average lifespan is about 60 years, but they can live to be over 100 years old.

Conservation status

Tuataras, like many native New Zealand animals, are threatened by habitat loss, and introduced species such as mustelids and rats. They were long confined to 32 offshore islands free of mammals.[1] A mainland release occurred in 2005 in the heavily fenced and monitored Karori Wildlife Sanctuary.

Sphenodon guntheri is present naturally on one small island with a population of approximately 400, and has been reintroduced to two others. Sphenodon punctatus naturally occurs on 29 islands and its population is estimated to be over 60,000 individuals.

There are several Tuatara breeding programmes within New Zealand. Southland Museum and Art Gallery in Invercargill, was the first to have a tuatara breeding programme; they breed Sphenodon punctatus. Hamilton Zoo and Wellington Zoo also breed tuataras for release into the wild. The Victoria University of Wellington maintains a research programme into the captive breeding of tuataras, and the National Wildlife Centre at Pukaha Mount Bruce keeps a pair and juvenile. The WildNZ Trust has a tuatara breeding enclosure at Ruawai.

Etymology and cultural significance

The name "tuatara" derives from the Māori language, meaning "peaks on the back".[8] Tuataras feature in a number of indigenous legends, and are held as ariki (God forms). Tuataras are regarded as the messengers of Whiro, the god of death and disaster, and Māori women are forbidden to eat them.[15] The tuatara is featured on one side of the New Zealand 5 cent coin, to be phased out in October 2006 .

Sphenodon is derived from the Greek language for "wedge" (sphenos) and "tooth" (odon(t)); punctatus is Latin for "spotted"; guntheri alludes to Albert Günther, keeper of Zoology at the British Museum in London.

This guide is licensed under the GNU Free Documentation License. It uses material from the Wikipedia.

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