Lizard or Not?
Although tuataras resemble lizards externally, they belong to the order Rhynhocephalia, which indicates that they roamed the earth at the time of the dinosaurs. Hence, they are also called living fossils.
The name 'tuatara' translates to "possessing peaks on the back" in the Maori language. According to Maori mythology, these reptiles were regarded as messengers of the God of Death and Disaster, Whiro. Endemic to New Zealand, this reptile is now extinct on the mainland and is found only on about thirty-odd islands of the New Zealand mainland.
They disappeared from the mainland due to rats and other predators brought in by the explorers of the New World. Rigorous efforts are underway to reintroduce them to the mainland and other islands.
Tuataras are said to be living fossils as they continue to possess the characters that squamates (ancestor of lizards and snakes) were known to possess. Today, there are two known species of tuatara, the Northern tuatara or Sphenodon punctatus and the Brothers Island tuatara or Sphenodon guntheri. The Sphenodon punctatus has two geographical variants inhabiting the Bay of Plenty and other northern islands.
Tuatara Lizard Facts
▶ These reptiles inhabit coastal forest regions and low scrubs. They usually prefer relatively open areas with loose soil. Tuataras are seen to cohabit with colonies of breeding birds, as their droppings improve the fertility of the soil, which may cause greater abundance of prey.
▶ Adult tuataras are nocturnal and terrestrial in nature. Juvenile tuataras are terrestrial, but are seen to be active during the day in order to prevent being eaten by adult tuataras.
▶ These reptiles, like any other, hibernate during winter. They can, however, remain active at very low temperatures, i.e., around 5°C and can survive in temperatures up to 27°C, beyond which it can be fatal.
▶ The optimum body temperature ranges from 16°C to 21°C .
▶ Another interesting fact about these reptiles is that they sometimes use the bird's burrows for shelter or they may dig their own.
▶ Both males and females are seen to be territorial in nature and tend to bite and seriously injure intruders.
▶ Adults usually molt once a year, whereas juvenile tuataras are seen to molt 3-4 times a year.
▶ These reptiles predominantly feed on insects like crickets, spiders, beetles frogs, worms, and other lizards. Older tuataras tend to feed on softer preys like insect larvae and earthworms.
▶ Sometimes, they feed on bird eggs and young ones. They are also believed to feed on their own young ones.
▶ Males are larger than females. The average length of the male is about 61cm and females is about 45cm; the Brothers Island tuataras being slightly smaller.
▶ Both males and females have spines on their backs. The spines on males are more prominent than those on females.
▶ The abdomen in males is seen to be narrower than those in females.
▶ There is a third eye or a parietal eye present on the top of the head of the juveniles, which is seen to possess its own lens and cornea, the innervation is seen to be highly degenerated. It is believed that this third eye plays a role in the circadian cycle, thermoregulation, and uptake of sunlight for the production of vitamin D. In adults, the parietal eyes is covered with opaque scales.
▶ Like turtles, tuataras also lack external ears; they show a response to frequencies ranging between 100 Hz to 800 Hz.
▶ The arrangement of teeth in these organisms is unique. The upper jaw contains two rows of teeth, whereas the lower jaw has only one row. The lower row is, sort of, wedged between the two rows in the upper jaw.
▶ Another unique feature about the teeth is that they are sharp projections of the jaws bones, and thus are irreplaceable.
▶ Males lack external genitalia.
▶ Tuataras can break off their tail when caught by a predator, which is regenerated by the organism later.
▶ Males and Females take almost 15-20 years to reach sexual maturity. They reproduce sexually and fertilization takes place internally.
▶ These reptiles reproduce once in 2-5 years, and the eggs need to be incubated for about a year to 15 months. Thus, they are the slowest reproducing reptiles.
▶ Females usually bury their eggs and leave them unattended. The sex of the young one depends on the temperature at which the eggs have been incubated. Eggs incubated at 22°C are more likely to be males, whereas eggs incubated at 20°C are more likely to produce females.
▶ These reptiles are seen to continuously grow over a period of 35 years. The average lifespan of these individuals can be up to 60 years in the wild, and more than 100 years in captivity.
▶ The greatest threat to the tuatara population comes from Polynesian rats as they prey on the young ones and steal eggs from the nests of these reptiles. As the rate of reproduction of these reptiles is very low, elimination of these rodents is essential for the survival of the tuatara population.
▶ The Northern tuatara is classified as Least Concern on the International Union For Conservation of Nature (IUCN) Red List with their population in the wild believed to be around 50,000 to 60,000.
▶ With only 473 adults spanning across an area of 2.2 hectares, the Brother Island tuataras are classified as vulnerable on the International Union For Conservation of Nature (IUCN) Red List.
▶ As these individuals have low genetic diversity, the population of tuataras is easily susceptible to a number of diseases that can be feared to have far-reaching effects on their population.