The new zealand lizard fauna includes members of two very widely distributed, almost cosmopolitan families, the Geckos (Gekkonidae), and the Skinks (Scincidae). The indigenous geckos (there are also some ‘recent’ arrivals and accidental importations) are of particular interest, for they are the only known ovoviparous (i.e. the eggs develop within the oviducts and the young are born alive) members of the family. In this respect they show a high degree of specialisation, possibly as a result of the environmental factors to which they are subjected. The skinks are also viviparous, but this feature is not confined to the New Zealand species.

Geckos are generally soft, loose-skinned lizards with small scales and no perceptible gloss. The head is comparatively large with a moderately well-defined neck. The pupil is a vertical slit in bright light, but in darkness or very dull light the pupil becomes round. The under side of the fingers and toes are provided with special suction plates called lamellae arranged cross-wise. These plates enable the animals to climb smooth surfaces, including glass.

Geckos are normally nocturnal, emerging from their hiding places under cover of darkness or in very dull light, or, sometimes, to bask in the sun. The Green Gecko (Naultinus elegans) is an exception. It is diurnal and spends its time in foliage.

Skinks, unlike the geckos, are clothed in a well-fitting armour of somewhat large, glistening scales — they are smooth and glossy. The head is not well differentiated from the body by a distinct neck. The pupil is round at all times. The toes are usually long and slender and there are no marked suction plates as in the geckos. Nevertheless, the scales are referred to as lamellae. Although skinks are able to climb on comparatively smooth surfaces, they are quite unable to negotiate surfaces such as glass.

Skinks are diurnal and fast moving. During the day they may be seen moving through vegetation and debris, but retire to their shelters for the night. They are also common on shingle strips and may be seen gliding between the shingle, though on the slightest sign of danger they make for shelter with amazing speed.

Many lizards are able to change their colour or their colour-patterns to suit the surroundings. However, there is a limit to the range of colour change. The changes take place very gradually, so that it is not till the page 46 change has been completed that it is noticed. Colour-change, to blend with the surroundings, screens the animals from their enemies — it is one form of camouflage in Nature. There are some colour forms of the Green Gecko (N. elegans) but none are able to change colour. In their natural habitat, foliage, they are well camouflaged. Hence, Green Geckos are often overlooked and appear to be comparatively rare.

With the above exception, our geckos are able to change colour or colour-pattern in harmony with their surroundings. Accordingly, the same species or individual may appear very different under altered conditions. Some of the South Island species of the genus Heteropholis are able to alter their colour tones but not the pattern.

Skinks exhibit a variety of colour phases in keeping with growth or season, but are not able to alter as geckos do. The colours are ‘fixed’, and the change observed is due to the amount and angle of light striking the animal at different points at a given moment. Accordingly, an animal in dappled light is difficult to see, especially when it is moving rapidly.

Geckos and skinks are found in almost all parts of the world. Their comparatively small size, secretive habits and ability to withstand long periods of fast are conducive to easy transport as ‘passengers’ on driftwood or in cargo. Their great plasticity enables them to survive and adapt themselves in suitable new environments.

The family Gekkonidae includes about 50 genera and some 280 or more species throughout the world. Three genera with a total of 10 species are indigenous and endemic within the limits of the faunal area of New Zealand. Some species of gecko is found almost throughout the area with the exception of the Chatham Islands where no geckos seem to be recorded. The Common Gecko (Hoplodactylus pacificus) is met with in most places, but often abundantly along the shingle beaches on the coast. Duvaucel's Gecko (H. duvauceli) is restricted to some of the islands in Cook Strait and off the northern shores of the North Island. The Forest Gecko (H. granulatus) and the Green Gecko (Naultinus elegans) appear to be confined to the forested area of the North Island and some of its off-shore islands. In the South Island, apart from the occurrence of the Common Gecko, the genus Heteropholis replaces the genus Hoplodactylus. Some of the species of the genus Heteropholis are, perhaps, among some of the most beautiful members of the family.

The family Scincidae comprises some 40 genera with about 600 species. Only two genera with 22 indigenous species occur within the limits of our fauna. Within our area the 38° S. parallel appears to form a natural boundary for some species, so that we find different species restricted to the areas north and south of that parallel. In addition, Cook Strait also forms a partial barrier. Other species are peculiarly insular. The Common Skink (Leiolopisma zelandica) is the most widely distributed and ranges from south of the 38° S. parallel all through the area, but is most commonly found along the shingle beaches. The Chatham Islands hold closely allied species.

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The New Zealand geckos, which are ovoviviparous, usually develop two eggs only in the ovaries. These eggs pass into the oviducts where the young develop until they are ready to emerge. Once the young are born the parent takes no further interest in them, and they must fend for themselves. The adults are generally very tolerant of the young and both young and old may be found living together under the same stone.

Skinks may produce one or more young at birth, as many as seven having been recorded from a single individual. Unlike the geckos, skinks are not tolerant of their young and will feed on them as readily as any other creatures they can overpower.

The period at which geckos are born varies with the species. The Common Gecko produces its young in late spring and early summer; Duvaucel's Gecko and the Forest Gecko somewhat later, about March to May; the Green Gecko is, perhaps, the latest breeder, producing its young at the end of May or early June.

Skinks produce their young about late spring onwards. Most young are born by the middle of summer. The time of birth may vary somewhat from place to place depending much on the climatic conditions.

The food of lizards consists mainly of small insects and other arthropods, but some show a distinct aversion to some forms of insect life and a preference for others. We have yet a lot to learn of the feeding habits of the individual species. Some will feed readily on plant secretions and honey (a useful food substitute for captive lizards). Geckos feed largely on flies, moths and beetles. Skinks on the other hand are more omnivorous and will feed on almost anything that they can overpower, including their own young and the smaller members of their own species. A favourite ‘diet’ of skinks is the tail of a neighbour! Skinks will also feed on berries and honey, and, on some of the islands, they will feed on the oil ejected by nestling birds, such as petrels, mollies, etc.

Both Geckos and Skinks drink water. The latter swim well and will deliberately sport in water.

Some lizards are able to shed their tails in the face of an enemy or on injury. Tail-shedding is a protective device which enables the animal to escape although it loses part of its reserve store. The wriggling of the detached tail distracts the enemy and allows the animal to escape to grow a new one. The new tail is never an exact replica of the original. Slight injury may result in a forked tail.

Periodically lizards shed their skin, or slough. With the increase in size, as growth proceeds, the skin becomes tight or worn and must be shed, just as we alter a suit! Young shed their skins more often than do adults. The exact periods at which the skin is shed and how often a year is not definitely known, but it appears to be approximately every two to three months in adults during the period when they are actively feeding.

Reptiles, being ‘cold-blooded’ animals, are largely dependent on the temperature of the air for their warmth and activity. When temperatures are too low lizards seek shelter and retire for the winter. In New Zealand page 48 there does not appear to be true hibernation, for, although lizards will seek shelter during the cold months, they will often come out of hiding on warm days to bask in the sun. During this period feeding is reduced to a minimum or they do not feed at all, but the animals are able to survive on the reserve they have stored up in their bodies during the warmer months of the year.

Both geckos and skinks, although of ancient lineage, still display a high degree of plasticity and, in consequence, a considerable power of variability. Their correct determination frequently constitutes a herpetologist's ‘headache’. A ‘foolproof’ key to such variable species is almost impossible. Hence the keys given below are only rough pointers — the full descriptions must be consulted for final determination of the species.

The keys have been extracted from a larger paper dealing with the Lizards of New Zealand — Bulletin No. 17 of the Dominion Museum, Wellington (1955).

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Before proceeding with the keys themselves it is, perhaps, advisable to differentiate between the two families:

Key to the Genera of New Zealand Gekkonidae

Key to Exotic Genera (Accidental Importations)

Key to the Species of Gehyra

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Key to the Species of Hoplodactylus

Key to the Species of Heteropholis

Key to New Zealand Scincidae