The gradual rise in sea level until it reached its present level 3-4 thousand years ago, isolated the Tuatara on many of New Zealand’s offshore islands. This island isolation has been their savoir. Since the arrival of the first humans about 1000 years ago, the range of Tuatara has since declined from both main lands to only 33 offshore islands. The main reasons attributed to this decline are that humans introduced predators and modified their habitat. (Image of Brother Islands)
Most of the Tuatara islands are difficult to access. Some are cliff-bound and frequently exposed to strong winds. The vegetation is stunted and salt tolerant. Many of the Tuatara inhabited islands have populations of breeding sea birds. The bird burrows honeycomb the islands’ surface. Although Tuatara are capable of digging their own burrows, some reluctantly share with a seasonally nesting sea bird.
The turning of the soil, with the addition of mineral enriched guano from the nesting birds, creates ideal conditions for ground dwelling insects like weta and darkling beetles, which form a major part of the Tuatara diet. Tuatara will also eat young sea birds, such as priors and petrels. They have also been reported to eat the bird’s eggs.
192-160 million years ago, New Zealand was connected to the great continent Gondwanaland with Australia, New Caledonia and Antarctica. At this time, Tuatara and other life forms, such as insects and amphibians, would have migrated to New Zealand. Continental plate movement separated New Zealand before mammals and snakes evolved, hence the only native mammals New Zealand has are two species of bat.
Tuatara do not like temperatures in excess of 28 degrees Celsius and can be active in cool temperatures where other reptiles and lizards are not so active. They have the ability to hibernate if the temperature becomes too cool, below 5 degrees Celsius.
Ultra Violet Light
Reptiles require exposure to the sun to regulate their body temperature. As they sun bath they absorb ultraviolet light rays that stimulate the production of vitamin D within the epidermis (layer under the skin). Long term without vitamin D, Tuatara will suffer from calcium deficiencies that effect bone and egg quality.