Compared with other countries New Zealand has few kinds of frogs and reptiles but the native frogs and the tuatara are among the world's most curious and interesting living fauna.
Reptiles are a class of vertebrate animals whose living forms include the crocodiles, turtles, snakes, lizards, and the lizard-like tuatara, found only in New Zealand. Apart from the tuatara, the reptile fauna of New Zealand consists of two kinds of lizards –geckos and skinks. Occasionally large marine turtles and sea snakes are recorded from New Zealand shores as strays from warmer northern waters. New Zealand has no terrestrial snakes and their importation for any purpose is forbidden.
New Zealand's lizards include only two families of the more than 20 known in the world. Both the geckos (Gekkonidae) and the skinks (Scincidae) are widely distributed families, but the New Zealand native geckos are the only members of this family to give birth to live young. All other geckos lay eggs.
Geckos are small, with a soft loose skin which is dull and granular in appearance. The pupil of the eye appears as a vertical slit in bright light, but in darkness it becomes large and round. Rough plates or lamellae on the underside of the fingers and toes enable the animal to climb smooth surfaces, even glass.
Geckos are nocturnal. The green gecko (Naultinus elegans) is an exception, for it shelters in foliage during the day, but other species emerge from their daytime hiding places only at dusk. Hoplodactylus pacificus, frequently found on shingle beaches, is probably the most commonly encountered New Zealand gecko. Duvaucel's gecko (Hoplodactylus duvauceli) which can attain 10 in. in length, is the largest species and is restricted to some of the islands in Cook Strait and to others off the northern coast of the North Island. The species of the genus Heteropholis found in the South Island are among the most beautiful members of the family.
Skinks are active, rapidly moving lizards which have a surface covering of shiny overlapping scales, smooth and glossy to touch. Skinks are distinguished by a slender head, neck, and body, and by long slender fingers and toes which lack the toe pads of geckos. They move about with amazing speed in hot weather, feeding and basking in the sun by day and retiring to shelter at night. The common skink, Leiolopisma zelandica, has a wide distribution and can easily be found on stony beaches.
Nine species of indigenous geckos and 18 species of skinks have been identified in New Zealand. Lizards sometimes come in with foreign cargoes, but none of these is known to have become established.
The frogs are members of the class Amphibia, a group of cold-blooded vertebrate animals whose larval young live in water and breathe by means of internal or external gills, and later metamorphose into an adult form which breathes air by means of lungs. The class includes the frogs, toads, newts, salamanders, and some limbless, wormlike, burrowing forms. New Zealand has a sparse amphibian fauna, limited to three species of native frogs and three frog species introduced from Australia in European times.
The native frogs belong to a genus (Leiopelma) restricted to New Zealand, which shows some of the most primitive skeletal and anatomical features of any known frog or toad.
Leiopelma archeyi occurs only on the Coromandel Peninsula, overlapping sometimes with Leiopelma hochstetteri which are also found in the coastal areas south of the Peninsula and at Warkworth and in the Waitakere Ranges. Leiopelma hamiltoni, the “Stephens Island Frog”, found on Stephens Island in Cook Strait, is now known to occur also on Maud Island in Pelorus Sound. The breeding of these frogs is of particular interest, for the few heavily yolked eggs laid are surrounded by a gelatinous capsule. The frogs undergo most of their development within this capsule and they hatch as well-developed froglets with a tail. At least two of the species are known to lack the free-living tadpole stage usually occurring in frogs. The native frogs are perhaps unique in that they are protected by law.
The introduced Australian frogs all belong to a single genus, Hyla, of a widespread family of tree frogs. The earliest successful introductions took place in 1867 and at least one of the species, the “Golden Bell Frog” (Hyla aurea), has become the most commonly encountered frog in both Islands. A second species, the “Brown Tree Frog” or “Whistling Frog” (Hyla ewingii), is found in Westland and in southern areas of the North Island. This frog produces a distinctive shrill piping call by means of vocal sacs on the throat.
The third species, the “Great Green Tree Frog” (Hyla caerulea), has rarely been found and possibly it is no longer present in New Zealand.
by Richard Essex Barwick, M.SC.(N.Z.), Lecturer, Zoology Department, School of General Studies, Australian National University, Canberra, A.C.T.