Tuatara
The tuatara (Sphenodon punctatus) is New Zealand's largest reptile and a unique species that has remained largely unchanged for approximately 220 million years. It is distinct from lizards, exhibiting a preference for cooler climates and a nocturnal lifestyle as an adult. Tuataras possess several unique features, such as a spiny crest on males used for mating displays and defense, a parietal eye located beneath the skin on their head, and a specialized dental structure with teeth that are fused to the jawbone. Their diet primarily consists of insects, birds, and their eggs, and they have a notably long incubation period for their eggs, which can take up to sixteen months to hatch.
Historically, tuataras were once widespread across New Zealand, but their populations declined dramatically due to introduced predators, leading to their extinction on the mainland by the early 1800s. Conservation efforts have been implemented since the 1980s, aimed at protecting remaining tuatara populations on offshore islands and restoring their habitats. As of 2006, it was estimated that around 100,000 tuataras remain, predominantly on islands like Stephens Island. Although currently classified as at risk and a relict species, ongoing conservation initiatives have shown promising results in stabilizing and potentially increasing their populations.
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Tuatara
The tuatara (Sphenodon punctatus) is an ancient species that has not changed much in 220 million years. It is New Zealand's largest reptile. Males can grow up to sixty centimeters in length. Females are shorter at a maximum of about forty centimeters. It is found only on islands off the coast of New Zealand.
Tuataras range in color from olive and gray to brown and orange-red. While the tuatara looks like a lizard, it is not one. It prefers cooler weather and is nocturnal when an adult, while lizards like warmer weather and are active in the daytime. In addition, tuataras have a different type of skeleton and do not have external ears as lizards do. Instead, they have openings on either side of their heads. Tuataras have a spiny crest down their necks, backs, and tails. This crest is made of folds of skin and is more developed in the male. Males use their crest for courting females and defensive purposes. Tuataras shed their skin every year and can regrow their tail if it breaks off.
Two unusual characteristics are the tuatara's parietal eye and teeth. Like many lizards and some other animals, the tuatara has a third eye, but it is more developed than in most species. The eye is located under the skin at the top of its head; it is visible in very young tuataras but gets covered with scales and pigment as it grows. It has a retina, but it is not used for seeing. Scientists are unsure of its function but think it may be used to absorb ultraviolet rays and to help the tuatara perceive the circadian and seasonal cycles.
The tuatara's teeth are different from all other reptiles. Instead of being separate structures, they are sharp bony projections of the jawbone. They have two rows of teeth on top and one row on the bottom. The bottom row fits between the top rows, which allows the tuatara to rip apart hard insects and birds. Tuataras primarily eat insects, birds, bird eggs, worms, millipedes, spiders, and lizards. They will also eat juvenile tuataras. Scientists speculate that this may be why juveniles are active during the day, rather than nocturnal.
Tuataras have an exceptionally long incubation time. Males mate every year, while females mate every four or five years. Males have no external reproductive organ. Reproduction occurs when the pair makes physical contact with their cloacal regions. The females lay soft-shelled eggs in a burrow about a year after mating. It takes eleven to sixteen months for the eggs to hatch. The soil temperature in the burrow determines the tuatara's gender, with higher temperatures producing more males. Lower temperatures stop the development of the eggs temporarily. Neither parent cares for the hatchlings. They grow very slowly and reach sexual maturity between ten and twenty years. They reach full adult size when they are about thirty years old and can live up to ninety years or more.
Brief History
Tuataras are descendants of a group of reptiles that belonged to the order Rhynchocephalia, also known as Sphenodontia. These reptiles were widespread over 200 million years ago and became extinct about 60 million years ago. Tuataras are the only surviving descendants. They have a very primitive body structure, with an exceptionally primitive heart. Some skeleton features are similar to those of fish.
Tuataras were once widespread throughout both North Island and South Island of New Zealand. Māori named the tuatara; the name means "spiny peaks." The tuatara is mentioned in several creation stories, and some Māori groups consider them guardians of knowledge. When the first people arrived in New Zealand around 1300 CE, they brought rats with them. Rats preyed on tuataras and steadily decreased their populations. By the time European settlers arrived in the early 1800s, tuataras were extinct on the mainland. They survived on about thirty-five offshore islands. Most of these islands had few native predators, and tuataras were able to coexist with the seabirds who use the islands to breed. The birds' guano provides a hospitable environment for the invertebrates and lizards tuataras live on.
Rats and other introduced animals, such as cats, dogs, and foxes, eventually made their way to some of these islands and preyed on tuataras. By 1895, the tuatara was classified as endangered. The New Zealand government gave protection to the tuataras and their eggs, but nevertheless, they became extinct on several of the islands. For example, in 1984 rats killed all the tuataras on a ten-hectare island within six months. In the 1980s, the New Zealand Wildlife Service (now the Department of Conservation) initiated a programme to rid the islands of rats and other non-native species. It also began a recovery program in which conservationists raised hatchlings until they were well developed and then released them in the wild on rat-free islands.
In 1989, a group of about six hundred tuataras was found on Brothers Island. Scientists initially believed this was a separate species of tuataras and named it the Brother Island tuatara (Sphenodon guntheri). In 2009, genetic research determined that in fact it was only a geographic variant of Sphenodon punctatus.
Tuataras Today
In 2024, the population was estimated to be around 55,000. The majority of tuataras live on about thirty offshore islands in Cook Strait and off the north-eastern coast of North Island. Stephens Island in Cook Strait has the most tuataras, about half the total population.
The IUCN listed the tuatara as a rare species between 1982 and 1994 and as near threatened in 2024. In its 2022 report, the New Zealand Threat Classification Series classified the tuatara as at risk, relict, which indicated it had declined in the last 1,000 years and presently occupies less than 10 percent of its former range, but has a stable or increasing population.
Climate change has negatively affected the tuatara population. Temperature affects the sex of a tuatara egg. Warmer weather causes tuataras to produce more males. Experts believed this has the potential to cause tuataras to become extinct.
Numerous conservation efforts have been made by the New Zealand Department of Conservation, researchers, wildlife groups and other conservationists. These include removing rats and other predators from islands, habitat restoration and management programs, captive incubation programs, and juvenile raising and translocation programs, as well as monitoring, researching and public awareness programs.
In 2005, a group of tuataras from Stephens Island were translocated to a wildlife sanctuary in Wellington. The tuataras survived and successfully bred in the wild. Other groups also have been relocated to the mainland. In 2012 groups of tuataras were relocated to several locations on South Island. Scientists regularly monitor these populations to assess their survival and whether they need to be moved to cooler locations.
Bibliography
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