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Tuatara Graces the Coins of New Zealand
 | By Dennis G. Rainey
December 05, 2007 |
On July 31, 2006, an interesting circulating coin depicting one of the most fascinating animals alive today sadly went out of circulation. The coin is the New Zealand five cents, first put in circulation in 1967 and honored a reptile, which is neither a lizard, snake, crocodilian or turtle. At first glance it looks like a large lizard but it is not a lizard. I wrote about this intriguing reptile in World Coin News 17 years ago (1990, Vol. 17, No. 1). What is it, and why am I devoting this column to this amazing animal? The reptile is the tuatara (Sphenodon punctatus), and in 2007 New Zealand issued $5 coins (KM 150) in cupronickel and silver honoring this reptile, and these are the latest in that nation's limited edition endangered animals coin collection. Also, in 2007 a new 10 cents commemorative uncirculated coin was issued with the same tuatara design. So, it is time to revisit this creature.
Tuatara is the Maori name and means "peaks on the back" from the crest of spiny scales on the head, neck, back and tail. Sphenodon refers to two wedge-shaped front teeth and punctatus refers to yellowish spots on the body of young animals. Exactly what kind of reptile is the tuatara if it is not a lizard? The genus is the only living representative of the reptilian order known as "beak-headed" reptiles, the members of which were common in the time of dinosaurs in many places on earth. The tuatara has not changed much in some 225 million years, and its closest relatives all died out about 60 million years ago, possibly due to the rise of true lizards. So, we are safe in calling the tuatara a "living fossil."
When I wrote about the tuatara in 1990 there was only the single species, S. punctatus, but now there are two with punctatus divided into two subspecies. In 1877 W. L. Buller described a new species of tuatara that he named Sphenodon guntheri, but this was ignored until 1990 when Charles Daugherty, et al., using genetics resurrected this species. Its common name is Brothers Island tuatara because it is found only on tiny North Brothers island in Marlborough Sounds. This species was named after Dr. Albert Gunther, curator of the British Museum in London, who was the first (in 1867) to declare tuataras were not lizards. (literature cites on request.)
The subspecies, S. p. punctatus, the northern tuatara, is found on numerous islands from the Bay of Plenty north on the east side of North Island, and an unnamed subspecies, the Cook Strait tuatara, is present on Stephens and Trio Islands in Marlborough Sounds between North and South Islands. In the past 100 years tuataras became extinct on 10 islands. S. guntheri is listed as vulnerable in the 2000 IUCN Red List and S. punctatus is lower risk.
In 2001, there were approximately 400 Brothers Island tuataras, 10,000 northerns and 45,000 (some say 50,000) Cook Strait tuataras. In addition to these wild tuataras, there are many captives in New Zealand and several places overseas. There is considerable international demand for tuataras (zoos, nature parks, researchers, etc.), and New Zealand authorities considers this to be a threat (possible poaching).
How do tuataras differ from lizards? Tuataras have a unique dentition. A single row of teeth in the lower jaw fits into a groove between two rows of teeth in the upper jaw. Also, the jaw movement when chewing allows for a shearing effect. The ribs have a small bone lacking in lizards and the males lack a copulatory organ (called hemipenes in lizards). Males fertilize females by pressing their cloaca (common opening of the digestive, urinary and genital tracts) against the females' cloaca and sperm passes to the females. Lizards have an external ear opening that is lacking in tuataras. Also, there is a "third eye" on top of the head that is visible only in very young animals as it is covered by scales in about six months. Its function is speculated to be the recipient of ultra violet rays from the sun that results in formation of vitamin D.
Lizards are cold-blooded, and typically they must bask in sunlight to get warm enough to conduct daily activities. Tuataras are also cold-blooded, however, adult tuataras are nocturnal and conduct their activities in the dark and at temperatures perhaps in the low 40s F. Sometimes adults do bask in sunlight for warmth. Very young individuals usually forage in daylight perhaps to avoid being eaten by adults. In general, tuataras require an optimal temperature range of 41 F to about 83 F, along with frequent heavy rainfall and high relative humidity.
Over the last 1,000 to 2,000 years tuataras have declined substantially. They occurred formerly on both North and South Islands but became extinct on both islands in the late 1700s. They now survive only on 35 offshore islands, three of which have had recent introductions. The 32 islands with wild tuatara populations were originally free of mammalian predators (rats and cats), and tuataras coexisted with breeding colonies of seabirds that added to the fertility of the islands thereby adding to the invertebrate and lizard fauna that tuataras ate. Tuataras share burrows dug by nesting shearwaters or mutton birds as they are called in New Zealand. Why have they survived only in New Zealand? Probably two factors are responsible - the cool climate and lack of mammalian predators on both North and South Islands and offshore islands.
Let's describe a tuatara. Males attain a length of about 2 feet with a long tail and weigh about 2 pounds in about 36 years. Females are smaller. The head is large and the crest of spines along the mid-dorsal line is larger in males. Color may be greenish or brown with specks of white or yellow. Hatchlings are brown or gray with a pink wash and striped throat. S. guntheri may be more brick red in color with noticeable light spots over the body and is slightly smaller. The average life span of Sphenodon is about 60 years, but it is said they can live to 100 years although there appears to be no confirmed record of living that long.
What are the causes of tuatara decline? Evidence points to the presence of rats - Norway rats (Rattus norvegicus), also called brown rats, the ship rat (Rattus rattus), also called house or black rat, and most importantly the Pacific rat (Rattus exulans), also called Polynesian rat. Pacific rats have been in New Zealand for some 1,000 years, but Europeans brought in the other two. Biologists found that on islands with rats the tuatara population was low, adults in poor condition and few juveniles. Studies indicated that rats ate tuatara eggs and babies, and were in direct competition for food resources (invertebrates, lizards and small petrels). It was found that when rats were eradicated from an island the tuatara population recovered. Some islands also had feral cats, which impacted tuataras. The New Zealand Department of Conservation has eradicated rats from all but three islands with tuataras.
What do tuataras eat? They consume crickets, beetles, moths, worms, snails, small lizards, small nesting seabird eggs and young birds (especially fairy prions and diving petrels).
It takes a long time for tuataras to have young due to their slow growth rate. Most of the research on reproduction has been done on Stephen's Island. They reach sexual maturity in 11-13 years, but males may not breed until much later because bigger males will prevent them from obtaining females as they are very territorial. Females breed at 13 years. Mating occurs in January to March, and the female will carry the eggs in her oviduct while shell formation occurs and laying is in October to December. The resulting fertilized eggs have a very slow rate of egg yolk production preventing females from breeding annually. The average time between clutches is four years.
Eggs (9-10) are laid in shallow excavations in the open and then covered to be incubated by the sun. The incubation period is 11 to 16 months, and many eggs are destroyed by desiccation, insects and other females covering their own eggs. Only about 42 percent make it to hatching, and the young are diurnal for some two months and then become nocturnal. It has been discovered that incubation temperatures influence the sex of the young.
The Department of Conservation has done a magnificent job in protecting and managing tuataras over the past several decades. There is an active DOC program to make citizens fully aware of their national treasure by promoting accessibility to captive individuals as they can even be handled without harm and also promoting controlled public access to certain wild populations. There has been a highly successful "tuatara road show" conducted by Victoria University. Through superb management, tuataras are safe from extinction for now.
A recommended publication from the New Zealand Department of Conservation is: Tuatara Recovery Plan 2001-2011. Threatened Species Recovery Plan No. 47. (Go to http://www.doc.govt.nz/ for the department's web site.)
If you are interested in the literature I have used, would like to make comments or have questions, you may contact me at denrain@charter.net.
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