Tuatara

Did you know tuatara animals are indigenous New Zealand lizards of the genus Sphenodon? The tuatara is a lizard-like reptile that is exclusively found in New Zealand. It is sometimes characterized as a living fossil from the dinosaur era!

Does that mean we have a living dinosaur species? Let’s find out. Despite their resemblance to most lizards, they belong to a separate lineage known as Rhynchocephalia. Their name comes from the Mori language and means "back peaks." The solitary species of tuatara (Sphenodon punctatus) is the only living member of its order, which evolved about 250 million years ago and thrived throughout the Mesozoic epoch. The squamates are their most recent shared ancestor with any other living group (lizards and snakes). As a result, the tuatara is of importance in the study of lizard and snake evolution, as well as the reconstruction of the appearance and behaviour of the earliest diapsids, a group of amniote tetrapods that also includes dinosaurs (including birds) and crocodilians. 

Tuatara Scientific Name

Sphenodon punctatus is the scientific name for the tuatara. The term "sphenodon" is derived from the Greek terms "sphen," which means "wedge," and "odon," which means "tooth." Punctatus is a Latin word for "pointed."

Tuatara Appearance

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Tuatara animals are greenish-brown and grey in colour, measuring up to 80 cm (31 in) from head to tail tip and weighing up to 1.3 kg (2.9 lb). Males have a spiky crest along the back that is especially prominent. They are the only extant species with two rows of teeth in the upper jaw that overlap one row in the lower jaw. 

They are also unique in that they have a prominent photoreceptive eye, the third eye (tuatara three eyes), which is considered to be important in the establishment of circadian and seasonal cycles. They can hear despite the lack of an external ear and have unique skeletal characteristics, some of which appear to have been maintained from fish evolutionarily. Tuatara animal is frequently referred to as "living fossils," which has sparked heated controversy among scientists. This word is no longer used by palaeontologists and evolutionary biologists. 

Despite the fact that tuatara has maintained the morphological features of their Mesozoic predecessors (240–230 million years ago), there is no evidence of a continuous fossil record to back this up. Researchers who have been sequencing its genome revealed that the species contains between 5 and 6 billion base pairs of DNA sequence, which is roughly twice that of humans. Since 1895, the tuatara (Sphenodon punctatus) has been legally protected. The Brothers Island tuatara (S. guntheri, Buller, 1877) was recognized as the second species in 1989, however, it has been reclassified as a subspecies since 2009. (S. p. guntheri). 

Tuatara Population

Tuatara populations - one of the world's oldest species - may be found on select tiny islands throughout New Zealand, as well as in an increasing number of mainland sanctuaries where tourists can have the rare opportunity of seeing this dinosaur survivor. Tuatara populations may currently be found on around 35 islands. Seven of these islands are located in Cook Strait, between Wellington on the southernmost tip of the North Island and Marlborough - Nelson on the southernmost tip of the South Island, and are home to an estimated 45,500 animals. An additional 10,000 northern tuatara live on islands around Auckland, Northland, the Coromandel Peninsula, and the Bay of Plenty.

Species

While there is presently only one extant species of tuatara, two have been identified: Sphenodon punctatus, or northern tuatara, and the rarer Sphenodon guntheri, or Brothers Island tuatara, which is restricted to North Brother Island in Cook Strait. The particular name punctatus is Latin for "spotted," and guntheri alludes to British herpetologist Albert Gunther, who was born in Germany. A 2009 research re-examined the genetic basis used to differentiate the two alleged species of tuatara, concluding that they simply reflect regional variations and that only one species should be recognized. As a result, the northern tuatara was renamed Sphenodon punctatus punctatus, while the Brothers Island tuatara was renamed Sphenodon punctatus guntheri. 

Based on jaw morphology, individuals from Brothers Island could not be differentiated from other current and fossil samples. The skin of the Brothers Island tuatara is olive-brown with yellowish patches, but the skin of the northern tuatara ranges from olive green to grey to dark pink or brick red, frequently mottled and always with white spots. Furthermore, the Brothers Island tuatara is much smaller. William Colenso discovered an extinct species of Sphenodon in November 1885 after receiving an imperfect subfossil specimen from a local coal mine. Colenso gave the new species the name S. diversum.

Tuatara- Endangered Species?

The tuatara, like many other native New Zealand species, is threatened by habitat loss and imported predators such as the Polynesian rat (Rattus exulans). Tuatara was extinct on the mainland, with the surviving populations restricted to 32 offshore islands, until 2005, when the first North Island release into the tightly guarded and monitored Karori Wildlife Sanctuary (now renamed "Zealandia") took place. 

While there are huge populations of tuatara on certain islands, and breeding programs are effective, the species is still threatened by predation.

When Polynesian immigrants came to New Zealand between 1250 and 1300AD, they brought with them kiore / Pacific rats that preyed on tuatara. The tuatara was nearly extinct on the mainland by the time European colonization began in the 1840s. While some islands afforded temporary refuge, they were soon overrun by rats and other animal predators brought by European immigrants. Tuatara and the islands they inhabited were accorded legislative protection as early as 1895, yet the reptiles continued to dwindle.

Are There Any Conservation Efforts Being Taken?

If you are wondering, if any conservation efforts are being taken to save tuatara, the answer is Yes! Hauturu / Little Barrier Island, located in the Hauraki Gulf between Auckland and the Coromandel, is an example of how a threatened tuatara population has been saved from extinction through conservation initiatives. When the Department of Conservation (DOC) began a captive management program on Little Barrier in 1991, no tuatara had been seen on the island for 14 years - though the rats thrived. Then eight adult surviving tuatara were located, caught, and kept secure from the rats.

The tuatara ultimately bred as a result of the safe habitat. The eggs were incubated in captivity, and the chicks were reared in rat-free environments. Kiore rats had been fully eliminated from the island by 2004, allowing for the release of juvenile tuatara back into the wild in 2006.

Do We have a Living Dinosaur Species Among Us?

The tuatara is a rare, medium-sized reptile endemic to New Zealand. An adult can reach a length of 24cm and a weight of 500 grams. Are tuatara lizards the same?

Though there are some physical similarities, it is not the same as lizards, crocodiles, or amphibians. Because of their basic body shape, they appear to have altered little in the last 220 million years, making them one of the world's oldest and most unevolved animals.

Because tuataras are sluggish breeders, they are vulnerable to predators. Females deposit soft-shelled eggs nine months after mating, with the eggs hatching in 12 to 15 months. The temperature of the soil determines the sex of the newborn. A juvenile tuatara can take anywhere from 9 to 14 years to grow, and they reach maximum size between the ages of 25 and 35. The tuatara can live for 60 to 100 years or more.

Behaviour

Adult tuatara is both terrestrial and nocturnal reptiles, however, they may frequently bask in the sun to warm themselves. Hatchlings are diurnal and hide beneath logs and stones, most likely because adults are cannibalistic. Tuatara survive at temperatures considerably lower than most reptiles can endure, and they hibernate during the winter. Temperatures as low as 5 °C (41 °F) keep them active, whereas temperatures above 28 °C (82 °F) are typically deadly. The tuatara's ideal body temperature ranges from 16 to 21 °C (61 to 70 °F), the lowest of any reptile. Tuataras have lower body temperatures than other reptiles, ranging from 5.2–11.2 °C (41.4–52.2 °F) during a day, although other reptiles have body temperatures around 20 °C (68 °F). 

A sluggish metabolism is caused by a low body temperature. During the breeding seasons, burrowing seabirds including petrels, prions, and shearwaters share the tuatara's island habitat. The guano of seabirds contributes to the survival of invertebrate species that tuatara mostly feed on, such as beetles, crickets, and spiders. They also consume frogs, lizards, and bird eggs and chicks. In complete darkness, no feeding attempts were seen, and the lowest light intensity at which an effort to snare a beetle was detected was 0.0125 lux. The eggs and young of seabirds, which are available periodically as food for tuatara, may provide beneficial fatty acids. 

Tuatara of both sexes protects their territories by threatening and finally biting intruders. The bite has the potential to cause significant damage. When confronted, a Tuatara will bite and will not release go easily.

Reproduction

Tuatara breed slowly, maturing sexually after 10 to 20 years. Mating takes place in the middle of summer, and females mate and lay eggs once every four years. A male darkens his complexion, raises his crests, and marches toward the female during courting. With tensed legs, he moves slowly in circles around the girl. The female will either yield and let the male ride her, or she will flee to her burrow. Males lack a penis and instead have rudimentary hemipenes, which are intromittent structures that transfer sperm to the female during copulation. 

The male lifts the female's tail and places his vent over hers to procreate. This is known as a "cloacal kiss" in some circles. The sperm is subsequently transported into the female, similar to how birds mate. The tuatara, like birds, is one of the only Amniota members that have lost the ancestral penis. Tuatara eggs have a delicate, parchment-like 0.2 mm thick shell made of calcite crystals embedded in a fibrous layer matrix. Females require one to three years to produce eggs with the yolk and up to seven months to develop the shell. From copulation until hatching, the process takes between 12 and 15 months. This implies that reproduction takes two to five years, which is the slowest of any reptile. 

At the age of 111, "Henry," a male tuatara at Southland Museum in Invercargill, New Zealand, became a father (perhaps for the first time). The sex of a hatchling is determined by the temperature of the egg, with warmer eggs creating males and colder eggs producing females. Eggs incubated at 21 degrees Celsius (70 degrees Fahrenheit) have an equal probability of becoming male or female. However, at 22 °C (72 °F), 80 percent of hatchlings will be males, and 80 percent will be females; at 18 °C (64 °F), all hatchlings will be females. Tuataras have one of the slowest growth rates of any reptile, becoming bigger over the first 35 years of their existence. The typical lifespan is around 60 years, but they may live to be well over 100 years old; the tuatara is the reptile with the longest longevity, except tortoises. At 111 years old, one of these males successfully bred for the first time with an 80-year-old female.

Cultural Significance

Tuatara appears in several indigenous stories and is revered as Ariki (God forms). Tuatara is considered messengers of Whiro, the deity of death and catastrophe, and Mori women are banned from eating them. Tuatara also represents tapu (the boundaries of what is holy and limited), beyond which there is mana, implying that crossing that barrier might have dire effects. The tuatara appeared on one side of the New Zealand five-cent coin, which was discontinued in October 2006. Tuatara was also the name of the journal published by the Biological Society of Victoria University College, and afterwards by Victoria University of Wellington, from 1947 until 1993. The New Zealand Electronic Text Centre, which is also located in Victoria, has now digitized it.

Popular Significance

• A tuatara named "Tua" appears heavily in John Green's 2017 novel Turtles All the Way Down.

• The tuatara inspired Tuatara, a member of the Global Guardians and a DC Comics superhero with a third eye.

• There is a Tuatara-themed craft beer brand in New Zealand that makes frequent use of the third eye in its advertising.

• The Tuatara hypercar, created and produced by SSC North America in Tri-Cities, Washington, is named after the reptile, citing its quickly changing DNA and "peaks on the back" as inspiration for the car's development.

• The Auckland Tuatara, one of two expansion clubs for the 2018/19 Australian Baseball League season, selected the tuatara name to honour the ancient reptiles' persistence and to raise awareness of New Zealand's dedication to species conservation.

• Tuatara Day is celebrated on May 2 to commemorate the day that the tuatara was discovered to be a bird rather than a reptile.

Age Determination

There are now two methods for identifying the age of a tuatara. Hematoxylinophilic rings in the phalanges and femur can be detected and quantified via microscopic examination. Tuatara can be treated with phalangeal hematoxylinophilic rings until they are 12–14 years old when they stop forming. Femoral rings follow a similar pattern, although they are only helpful for tuatara between the ages of 25 and 35. Femoral rings stop forming at that age. Because tuatara lives for considerably longer than 35 years, more study on age determination methods for tuatara is needed. Examining tooth wear and tear is one option, as tuatara have fused pairs of teeth.

What do Tuataras Eat?

Because tuataras are unusual among reptiles, many people wonder, "What do tuataras eat?"

In this regard, tuataras are similar to many other lizards and reptiles of comparable size. Beetles, earthworms, crickets, and spiders are their primary prey. They have been observed eating snails, frogs, bird eggs, skinks, and even their own young in the absence of these insects.

Tuatara Predators and Threats

Tuataras alternate between being listed as an endangered species and being listed as “at-risk” or “vulnerable,” which is a step below. However, due to effective conservation efforts, the IUCN has upgraded it to the least concern.

The greatest severe threat to wild tuataras is the introduction of mammalian predators to the islands through human settlement. Dogs and rats have had the greatest influence on tuatara populations, although other species like ferrets and cats have also had an impact. Because imported predators devastated natural tuatara populations in such a short period of time, the New Zealand government proclaimed tuataras and their eggs entirely protected in 1895. That protection is still in place today, and it helps to keep their numbers from diminishing.