Tuatara are New Zealand’s own dinosaurs of very ancient lineage. They have remained virtually unchanged since walking with other dinosaurs some 100 million years ago. They are long-lived (50-plus years) and don’t breed until they are 10 to 15 years old. They produce eggs only every two to five years. They can lay between four and 13 eggs and these are buried in the soil and can take 10 to 16 months to hatch. The sex of the hatchlings depends on the incubation temperature. Temperatures greater than 22C produce males, and females are produced at temperatures below 22C.
They have some interesting quirks, such as no ears or eardrums and a third eye in the middle of their foreheads that can sense light and is particularly sensitive in juveniles.
Sedentary tuatara can move quickly if required.
They are cold-blooded, so their metabolism depends on the temperature of their environment. The warmer it is, the quicker they can move. Tuatara can remain active at quite low temperatures. They have two rows of teeth in their upper jaws and one row in their bottom jaw that lock together to mangle their prey. They are sedentary predators, feeding on what walks past them, such as insects, skinks and geckos and young seabird chicks, though they can move quickly if required. They are often found living among seabird colonies, sometimes even sharing their burrows. They are nocturnal, but enjoy sun-basking.
Juveniles are often more obvious in the daytime; one reason is the belief that this helps prevent them being eaten by adult tuatara. Tuatara were once widespread throughout New Zealand, but now survive on predator-free islands and in some mainland sanctuaries.
Te Hauturu o Toi/Little Barrier Island has its own dinosaurs. Tuatara probably arrived on Hauturu with other flightless creatures when the sea level was much lower, some 18,000 years ago in the last Ice Age. Hauturu was then connected to Aotea/Great Barrier and Coromandel by a vast plain that is now the Hauraki Gulf/Te Moananui o Toi. Much later humans arrived on the island bringing with them predators such as kiore and, later, cats.
By 1980, cats had been removed from Hauturu, but kiore remained and it appeared that very few eggs or young tuatara were surviving. A survey in 1990 found only eight adults, four of each sex. A breeding programme was started with these eight animals being housed in an enclosure, provided by the Little Barrier Island Supporters Trust, to protect them from predation by kiore. For many years, the trust working weekenders would weed and prune in these enclosures, with the added bonus of maybe spotting a tuatara. The trust also provided some funding towards extra food supplies for the growing population. This breeding programme lasted almost 25 years, aided by Victoria University taking eggs to incubate to ensure the best outcome and an even mix of male and female hatchlings. The young were then returned to the island.
In 2004, kiore were removed from the island and the juvenile tuatara could be released. By 2017, some 290 juveniles had been released back into the wild.
The breeding programme was deemed a great success and has now been discontinued. Tuatara are now free to roam and breed on the island once again.
Lyn Wade, Little Barrier Island Supporters Trust