Skinks and geckos
New Zealand has two types of land reptile – lizards and the tuatara. Lizards are a diverse group worldwide, but in New Zealand there are only two families – skinks (Scincidae) and geckos (Gekkonidae).
There are two genera of New Zealand geckos and one genus of skink, in each of which there are many species. The gecko genera are found nowhere else, while species in the skink genus are also found on Norfolk and Lord Howe islands. Although these islands are Australian territories, their plants and animals are closely related to those in New Zealand.
It is not certain how many skink and gecko species there are in New Zealand. The last review, published in 1994, listed 62, many of which were yet to be named. Since then, species have been discovered faster than taxonomists can describe and name them. There are probably at least 80 species that are endemic (occur only in New Zealand). New Zealand has more lizard species relative to its land area than many other countries. It can be difficult to identify them, as the most up-to-date field guide, New Zealand frogs and reptiles (1996), does not include all known species.
There is only one introduced lizard species – the rainbow skink (Lampropholis delicata), which probably arrived from Australia in a ship’s cargo.
Skinks and geckos are easily distinguished:
- Skinks are smooth-skinned, sleek and shiny, with small legs. They have small eyes and can blink.
- Geckos have scaly skin that feels silky and looks one size too large, and stout legs. Their eyes are large and cannot blink.
Most of New Zealand’s skinks and geckos are small, and the few species people usually see are dull-coloured. Until recently these lizards attracted little attention from zoologists.
New Zealand lizards are unusual in that only one, the egg-laying skink, lays eggs. The others are viviparous – they give birth to live young. The eggs hatch in the female’s oviduct before the youngsters are born. Common skinks (Oligosoma nigriplantare) and possibly other species grow a placenta, and the developing embryo is nourished by its mother. Vivipary is thought to be an adaptation to New Zealand’s cooling climate during the ice ages – most other viviparous lizards occur in colder regions of the world.
New Zealand skinks and geckos produce fewer young than most species overseas. New Zealand geckos normally have two young each time they breed. Most breed once a year, but Duvaucel’s gecko (Hoplodactylus duvaucelii) and the Macraes (Central Otago) gecko (H. maculatus Macraes form) breed every second year. A Macraes gecko’s pregnancy lasts 14 months, perhaps because cool temperatures slow the foetus’s development. Most other New Zealand geckos mate in spring or summer and give birth in autumn or winter.
Skinks usually have between two and five young at yearly intervals.
New Zealand lizards have unusually long lives. One Duvaucel’s gecko lived for at least 36 years, and many of the smaller common geckos live more than 20 years. Skinks do not live as long – the largest live about 10 years.