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Tuataras (Sphenodon punctatus)



Tuataras (Sphenodon punctatus)
The two recognized species of tuatara (Sphenodon punctatus and Sphenodon guntheri) are found on approximately 30 small, relatively inaccesible, islands off the coast of New Zealand. The species was once widely distributed throughout New Zealand, but became extinct on the mainland before the arrival of European settlers



Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Reptilia
Order Rhynchocephalia
Family Sphenodontidae
Species Sphenodon punctatus

Habitat

The geographic range which the tuatara inhabits is a difficult niche for any species, particularly a reptile. The islands are generally cliff-bound, frequently exposed to strong winds, and support a natural, often stunted, vegetation of salt and wind tolerant species. Most islands are also home to several species of sea birds, whose nutrient-rich guano helps support the island's ecosystem. The habitat is cold and damp, with temperatures rarely exceeding 70 degrees Fahrenheit, and a humidity level of about 80 percent. The temperature may often approach freezing, but the tuatara is able to maintain normal activities at temperatures as low as 45 degrees Fahrenheit. Preferred body temperature is between 60 and 70 degrees, this is the lowest optimal body temperature of all reptiles. At temperatures above 76 degrees, tuataras show signs of distress, and most will die if the temperature exceeds 82 degrees.
 
Physical Description
Mass
0.40 to 1 kg
(0.88 to 2.2 lbs)


Tuataras may be grey, olive, or brickish red in color. They range in adult length from about 40 cm (female) to 60 cm (large male), with the male generally reaching larger proportions. They lack external ears, have a diapsid skull (two openings on either side), and posess a "parietal eye" on the top of their head. Other lizards also have this "third-eye," which contains a retina and is functionally similar to a normal eye, though the function has not been clearly recognized and a scale grows over it in adult tuataras. The male tuatara displays a striking crest down the back of the neck, and another down the middle of the back. The female has a less developed version of this. Unlike all other living toothed reptiles, the tuatara's teeth are fused to the jaw bone (acrodont tooth structure). The tuatara has a very slow metabolism and is a very long-lived species. It's not uncommon for an individual to live for over 100 years.
 
Reproduction

It takes between 10 and 20 years for a tuatara to reach sexual maturity. The female, on average, lays between 5 and 18 eggs only once every 4 years, the longest reproductive cycle of any reptile. Mating occurs from mid-summer to early autumn (January-March) and the eggs are laid the following spring or early summer (October-December). Incubation takes from 12 to 15 months, with the development of the embryo stopping during the winter months. Thus, a hatchling tuatara would have been conceived over two years earlier. The male is devoid of any external sex organs, and copulation is achieved by a meeting of the cloacal regions in what is known as a "cloacal kiss."
 
Behavior

Tuataras live singly in burrows, which they sometimes defend. Males combat each other, inflating their bodies, elevating their crests, and darkening the skin between the shoulders and neck crest. Males also approach females in this manner prior to breeding. Tuataras are most active at night, but occassionally bask at the entrance to their burrows if it is sunny.
 
Food Habits

Diet consist of arthropods, earthworms, snails, bird eggs, small birds, frogs and lizards, and a native cricket-like insect the size of a mouse called a weta. Young tuataras are also occassionally cannibalized. Due to its low metabolic rate, the tuatara eats much less frequently than other reptiles.
 
Conservation Status

In 1895, the country of New Zealand awarded the tuatara strict legal protection. It is currently considered a CITES (Convention on the International Trade in Endangered Species) Appendix I species. This is the most restricted classification for a species. In order for a zoo to posess this species, very demanding rules must be followed, and the public display of tuataras has only recently been allowed. Access to the islands that the tuatara inhabit is strictly regulated, and for many years no tuataras have been removed from any island for any reason.
 
Other Comments

The tuatara is the only living descendent of the order of reptiles known as Rhynchocephalia. This fact distinguishes it from all other modern day reptiles. Rhynchocephalians were a much larger order of reptiles a few hundred million years ago, with a considerable number of species during the Triassic period. All except for the tuatara apparently went extinct around 60 million years ago, in the late Cretaceous period. The tuatara has been falsely called a living fossil. Though very similar to its extinct ancestors, it has developed features unique to its own modern species. As well, it has been likened to a living dinosaur, due to its diapsid skull and other anatomical features shared with prehistoric reptilians.

Contributors
Bruce Musico (author), University of Michigan.

References
Newman, Don. 1987. "Tuatara." Endangered New Zealand Wildlife Series. John McIndoe, Limited. Dunedin, New Zealand.

 
Wright, Kevin DVM. 1994. "Tuataras." Vol.2, No.1. Reptiles magazine. Fancy Publications. Irvine, California.
 
Robb, J. 1977. The Tuatara. Meadowfield Press, Limited. Durham, England. 




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Musico, B. 1999. "Sphenodon punctatus" (On-line), Animal Diversity Web. Accessed June 20, 2006 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Sphenodon_punctatus.html.

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