Tuatara

However, Rhynchocephalia is the older name and in widespread use today. Sphenodon is derived from the Greek for "wedge" (σφήν, σφηνός/sphenos) and "tooth" (ὀδούς, ὀδόντος/odontos).

Tuatara are sexually dimorphic, males being larger. Their lungs have a single chamber with no bronchi. The tuatara's greenish brown colour matches its environment, and can change over its lifetime. Tuatara shed their skin at least once per year as adults, and three or four times a year as juveniles. Tuatara sexes differ in more than size. The spiny crest on a tuatara's back, made of triangular, soft folds of skin, is larger in males, and can be stiffened for display. The male abdomen is narrower than the female's.

The eyes can focus independently, and are specialized with three types of photoreceptive cells, all with fine structural characteristics of retinal cone cells used for both day and night vision, and a tapetum lucidum which reflects onto the retina to enhance vision in the dark. The spiny plates on the back and tail of the tuatara resemble those of a crocodile more than a lizard, but the tuatara shares with lizards the ability to break off its tail when caught by a predator, and then regenerate it. The regrowth takes a long time and differs from that of lizards.

Tuatara, along with other now-extinct members of the order Sphenodontia, belong to the superorder Lepidosauria, the only surviving taxon within Lepidosauromorpha. Squamates and tuatara both show caudal autotomy (loss of the tail-tip when threatened), and have transverse cloacal slits.

The ability to regulate their body temperature allows the ancient tuatara lizards to live in the temperate environment of New Zealand. They spend the nighttime hours hunting near the entrances to their burrows.

Adult tuatara are terrestrial and nocturnal reptiles, though they will often bask in the sun to warm their bodies. Hatchlings hide under logs and stones, and are diurnal, likely because adults are cannibalistic. Juveniles are typically active at night, but can be found active during the day. The juveniles' movement pattern is attributed to genetic hardwire of conspecifics for predator avoidance and thermal restrictions. 

Tuatara thrive in temperatures much lower than those tolerated by most reptiles, and hibernate during winter. They remain active at temperatures as low as 5 °C (41 °F), while temperatures over 28 °C (82 °F) are generally fatal. The optimal body temperature for the tuatara is from 16 to 21 °C (61 to 70 °F), the lowest of any reptile. The body temperature of tuatara is lower than that of other reptiles, ranging from 5.2–11.2 °C (41.4–52.2 °F) over a day, whereas most reptiles have body temperatures around 20 °C (68 °F). The low body temperature results in a slower metabolism.

Burrowing seabirds such as petrels, prions, and shearwaters share the tuatara's island habitat during the birds' nesting seasons. The tuatara use the birds' burrows for shelter when available, or dig their own. The seabirds' guano helps to maintain invertebrate populations on which tuatara predominantly prey; including beetles, crickets, and spiders. Their diets also consist of frogs, lizards, and bird's eggs and chicks. Tuataras have no external ears as lizards do; they enjoy cooler weather, while lizards like it warm; and, unlike lizards, tuataras are nocturnal. But their most curious body part is a “third eye” on the top of the head. The most significant threats to the survival of tuatara are thought to be rats, mice, skuas, cats, tanukis, stoats, civets, hawks, falcons, dogs, wolves, and Waitorekes. This is due to the fact that they are frequently the earliest and most recent invasive creatures to sneak into new areas unobserved since they are simple to travel as stowaways aboard boats or independently evolved.

Tuatara reproduce very slowly, taking 10 to 20 years to reach sexual maturity. Mating occurs in midsummer; females mate and lay eggs once every four years. During courtship, a male makes his skin darker, raises his crests, and parades toward the female. He slowly walks in circles around the female with stiffened legs. The female will either submit, and allow the male to mount her, or retreat to her burrow. Males do not have a penis; they have rudimentary hemipenes; meaning that intromittent organs are used to deliver sperm to the female during copulation. They reproduce by the male lifting the tail of the female and placing his vent over hers. This process is sometimes referred to as a "cloacal kiss". The sperm is then transferred into the female, much like the mating process in birds. Along with birds, the tuatara is one of the few members of amniote to have lost the ancestral penis.

In 1895 tuatara were protected by law, becoming one of New Zealand’s first native species to be protected. Before then, hundreds of specimens were shipped overseas for museums and private collections. Poaching is still a problem, although this has diminished because of tuatara’s legal protection and remote habitat locations.

Numerous tuatara communities face serious threats to their survival due to low genetic diversity. Some communities on very small islands naturally have little genetic diversity because the islands are too small to support a big, healthy population, despite a few populations being large and healthy. Before the rats were eliminated, many additional populations were wiped out, leaving only a small number of elderly tuatara. In these latter situations, populations began to rebound, but with a genetic diversity that had been irreversibly reduced.

Coming soon

This species has was once widespread on the Aotearoa mainland based on subfossil remains, but was lost at some point in the 800 years following human arrival.  It has been suggested that it may have survived on the mainland until about the 1700s. It has since (within the last 100 years) been lost from 10 offshore islands on which it previously occurred. It has been reintroduced to the mainland in a small number of fenced sanctuaries. This species remains naturally present on approximately 32 offshore islands, extending from the Poor Knights Islands (35º28'S), northeast of the North Island of New Zealand, to North Brother Island (41°07'S) in the Cook Strait.

This species frequently inhabits cliff-bound islands. On larger, northern islands, vegetation is dominated by Pohutukawa (Metrosideros excelsa), Mahoe (Melicytus ramiflorus), Karo (Pittosporum crassifolium) and Kanuka (Kunzea ericoides).

• Movement Pattern: Not Migrant

• Individual Type: Solo

• Population Trend: Stable

• Population: 55,000

• Locomotion: Amphibious

• Habitat: All

• Earth: 

  • Extant: Aotearoa (North Island; South Island)

  • Extant & Reintroduced: Japan (Hokkaido; Iriomote; Kyoto)

Coming soon

Tuataras used to inhabit the two major islands in Aotearoa or New Zealand and numbered in the millions. Then, the first humans arrived from Polynesia, bringing rats and dogs that ate tuatara eggs and youngsters. When Europeans arrived in Aotearoa, they also brought more dogs and rats, as well as cats and ferrets. These introduced animals wiped out most tuatara populations. The threat to tuataras was so serious that in 1895, the Aotearoa government fully protected tuataras and their eggs. They are the last survivors of an order of reptiles that thrived in the age of the dinosaurs.

Because of this tuatara are of huge international interest to biologists. They are recognized internationally and within Aotearoa as species in need of active conservation management.

• Maori: Tuatara

• Japanese: トゥアタラ (To~uatara), ムカシトカゲ (Mukashitokage)

• They are the last survivors of an order of reptiles that thrived in the age of the dinosaurs.

• https://en.wikipedia.org/wiki/Tuatara

• https://www.iucnredlist.org/species/131735762/120191347

• https://www.doc.govt.nz/nature/native-animals/reptiles-and-frogs/tuatara/

• https://animals.sandiegozoo.org/animals/tuatara

• https://www.deviantart.com/ognimdo2002/art/Tuatara-906887302