Each of the two gecko genera has a preferred environment:
- The green geckos in the genus Naultinus are diurnal and tree dwelling.
- The mostly grey or brown Hoplodactylus geckos are nocturnal, and live on the ground or in trees.
Some Oligosoma skinks are diurnal and live mostly in open habitats, while others are nocturnal and live mainly in damp, thickly vegetated lowland areas in northern New Zealand.
Some lizard species are widespread, but others need particular habitats. For example, the Fiordland skink (Oligosoma acrinasum) lives only on foreshore rocks and boulder beaches on the Fiordland coast. The egg-laying skink (O. suteri) forages near rock pools and in the intertidal zone of the northern North Island. The scree skink (O. waimatense) is found only on unstable screes in mountains of the eastern South Island. The species with one of the most limited distributions – and arguably the most extreme habitat – is the black-eyed gecko (Hoplodactylus kahutarae). It lives only on alpine bluffs 1,300–2,200 metres above sea level in the Kaikōura Range and on Mt Arthur, near Nelson.
Sun and snow
Most lizards worldwide live in warm climates, yet the South Island’s subalpine tussocklands are a centre for lizard diversity. Many species occur only in these regions, which have an extreme climate. In summer, temperatures can exceed 30°C by day then drop below freezing at night. Snow can cover the ground for weeks in winter, and may fall even in summer. How these small reptiles can cope with such extreme conditions is not known.
Diversity in cold regions
There is an unusual diversity of species in the colder parts of the country. Lizards rely on the sun for warmth so are more common in warm climates worldwide. Yet at least six species occur on cool Stewart Island, and at least eight are in the South Island high country. Of these, two are active at night when temperatures are coolest: the harlequin gecko (Hoplodactylus rakiurae), which is found only in the southernmost parts of Stewart Island, and the alpine black-eyed gecko.
Today, at least one species of small diurnal skink and a small nocturnal gecko can be found virtually everywhere in New Zealand, except in some urban areas where cats have killed most lizards. There were many more species before mammalian predators were introduced. For example, Northland once had more than 17 species of lizards. Up to 12 still live on some rat-free northern islands, but only eight remain on the mainland.
Lizards are easy to miss, but they can be surprisingly common. In suitable microhabitats there may be one lizard per square metre. At Pukerua Bay, north of Wellington, there are about 4,900 common skinks per hectare, as well as lesser numbers of several other species.
Skinks and geckos eat insects. Some species also eat fruit or nectar, and lizards on islands will eat the partly digested food spilt by seabirds feeding their chicks. The large scree skink includes smaller lizards in its omnivorous diet.
Pollinators and seed dispersers
Insect-eating lizards are not usually associated with pollination and seed dispersal. But geckos drink nectar from the flowers of a number of native plants, including cabbage trees, flax, southern rātā and pōhutukawa, and presumably transfer pollen from one plant to another. They are probably not crucial to pollination, as the flowers are also visited by birds or insects. Some lizards eat fruits of certain tightly divaricating plants such as mingimingi (Coprosma propinqua), which produce small blue or black berries and seem to rely primarily on lizards to disperse them.