From a herpetological point of view, New Zealand may not be the most species rich country in the world but it is nevertheless interesting. Part of the Australo-Pacific area, and the furthest major islands south of that zone, it has a surprisingly high number of endemic species for what is in fact a temperate climate. These species, notably the skinks and geckos, show adaptations to cope with this. At the same time the current state of New Zealand's herpetological fauna stands as a warning against what can happen if the ecology of a land is not taken into account, as many of its endemic reptiles and frogs are now restricted to a few offshore islands where they are rigorously protected by human agency.
The herpetofauna of New Zealand has been largely dictated by the isolation of the country and its distance from other land masses. New Zealand and New Caledonia are the visible parts of a continental crust known as Zealandia. Australia and Zealandia once formed part of the supercontinent Gondwana but split from the latter in the Cretaceous era, 90-95 million years ago. At some point in the Cretaceous it also split from Antarctica, and around 83 million years ago began to separate from Australia, this process forming the Tasman Sea that now separates the two countries. By 75 million years ago, Zealandia was separated from both Australia and Antarctica. Much of the continent was subsequently submerged by about 23 million years ago, and remains so today. Robb suggests that the Lord Howe Rise to the north of New Zealand may once have provided islands and land as stepping stones from the rest of the world to New Zealand before it too became largely submerged, so that now only Lord Howe Island, a comparatively recent volcanic extrusion, remains above sea level.
Thus New Zealand's flora and fauna had already been isolated from the rest of the world early in the Tertiary Period. In parts of South Island, particularly Fiordland, the wildlife was then further tested by the glaciation of the Ice Ages, in particular the Last Glacial Maximum about 20,000 years ago, though most of the country was unaffected. The lowering of sea levels in this period did however mean that both North and South Islands were joined to each other and to Stewart Island.
Human impact on the herpetofauna (and indeed avifauna) of New Zealand came in two waves. The first was the Maori settlement that commenced around 1280 AD, before which New Zealand is believed to have been unpopulated by humans and to have had only a small number of mammals, including marine species. Apart from their own immediate impact on the birds of New Zealand by their hunting, the Maori also brought with them the Kiore or Polynesian Rat, Rattus exulans. The rodent, implicated in other extinction events on Polynesian islands by its commensal travel with the Polynesians, has a very adaptable diet and includes lizards and eggs in its prey items. Although the species restricts breeding to spring and summer rather than being constantly fertile as its congenerics in other parts of the world, the kiore was still able to spread throughout the islands. By the sixteenth century all species of moa had become extinct.
The second wave took place during the European visits to the islands, commencing in the seventeenth century. Settlement of Europeans began in earnest in the nineteenth century, and partly in response to the lawless behaviour of some of the settlers, the British effectively took over the running of the islands in 1840. The real impact came however with the accidental introduction of other rodents on to the islands from visiting ships (these being notorious for unwillingly carrying rats and mice with them), the first Rattus norvegicus believed to have come (ironically) from Captain James Cook's ship, the Endeavour. Rabbits were introduced in the 1800s, the Australian bush-tailed possum in 1837, the Australian magpie in 1860, hedgehogs in 1873, and ferrets and stoats and weasels between 1879-1885 in an attempt to control the rabbits. By 1860 the ship rats had spread throughout North Island, and just ten years later had achieved the same in South Island. Another well-meaning but ultimately detrimental step was the forming of Acclimatisation Societies, a move that started in France but which was enthusiastically adopted in English speaking dominions such as New Zealand. The societies sought to introduce fauna and flora from their home countries into the lands they now occupied, either for agricultural or commercial purposes (including also recreation in the form of hunting and fishing) or in the belief that the local wildlife was somehow impoverished. One source has suggested that nostalgia for the "old country" may also have played a part. Whatever the reasons, the impact of a large number of non-native mammalian species in a largely reptilian- and avian-dominated ecosystem was profoundly negative. The societies themselves soon realised that they had unleashed problems, even without reference to the native fauna, as the introduced small birds became a nuisance to the farmers and red deer had become a pest by the 1930s. Even so the attitude that native predators on valuable introduced annimals were pests took a long time to die out. There also appears to have been little interest in the native herpetofauna at times: for example, Chapple et al point out that almost nothing was published on the distinctive skinks of New Zealand for the first half of the twentieth century.
The twentieth century saw a revision of attitudes. Although the introduced animals could not all be removed, a large number of national parks was set up, protection removed from some non-native mammals and given instead to endemic species. Active measures included the removal of rats from Kapiti Island and the reintroduction of threatened native birds there, and the saving of the Black Robin (Petroica traversi) from extinction.
For such a temperate climate the amphibian diversity is surprisingly low. The absence of tailed amphibians (newts and salamanders) is not so surprising given that most of these are found in the northern hemisphere and are absent from the Australo-Pacific region, but the paucity of tailless amphibians (frogs and toads) is perhaps more so. The native species all belong to the genus Leiopelma of the Family Leiopelmatidae, the so-called "tailed frogs" which are considered primitive and for that reason all the more interesting. These frogs are now confined to small pockets on outlying islands. Their places have been somewhat supplanted by three Australian frogs imported in the nineteenth century: Litoria aurea, L. ewingi and L. raniformis. It is interesting however that nineteenth century attempts to establish European anuran species such as Bufo bufo, the Common Toad, Rana temporaria, the Common Frog, and Rana esculenta, the Edible Frog (this latter apparently intended as food for wild ducks in Nelson), were unsuccessful, particularly given the experience of neighbouring Australia with the Cane Toad Bufo marinus. Perhaps the Cane Toad is simply bigger and hardier, or the introduction of the New Zealand amphibia was simply not handled carefully.
In some ways the reptilian fauna of New Zealand is unique in that for such a relatively large landmass the country has no tortoises or turtles, nor snakes, although marine turtles and marine snakes do appear around the shores. Since both orders of animal were already present when Zealandia started breaking away from Gondwana, their absence is perhaps more explicable in terms of oviparity being difficult in cool climates (though this has not prevented the tuatara's survival - see below), and of the subsequent difficulty for such creatures in rafting later to New Zealand, a proven method of colonisation for lizards. However, so far there has been an absence of fossils to confirm whether or not either order of animal did ever exist in New Zealand, so much remains conjecture. The absence of amphisbaenia, a group of legless, burrowing reptiles largely confined to the tropics, is less surprising since although relatively common in South America these have not been found so far in the Australo-Pacific region.
Some chelonians were subsequently imported into New Zealand in the nineteenth and twentieth centuries, including Chelodina longicollis, the Australian Common Long-Necked Tortoise, Trachemys scripta elegans, the Red-Eared Slider from North America, Testudo graeca, the Greek Tortoise from Europe, and Terrapene carolina, the Carolina Box Turtle (again from North America). For the most part these turtles did not thrive and most died within a relatively short period, even the normally hardy Red-Eared Sliders which have been so invasive elsewhere. Breeding only seems to have been successful where eggs were taken and incubated by human agency. Robb has details on these introductions, as well as a reference to an isolated story of a "small land tortoise" whose authenticity appears doubtful.
Of the marine turtles, the following are known to visit New Zealand, at least on occasion: the Leatherback, Dermochelys coriacea; the Green Turtle, Chelonia mydas; the Pacific Loggerhead, Caretta caretta gigas; and the Hawksbill, Eretmochelys imbricata squamata. Marine snakes known to visit New Zealand are all members of the Hydrophiidae: Pelamis platurus, the Yellow-Bellied Sea Snake with the widest distribution of any sea snake in the world, and the banded sea snakes Laticauda colubrina and L. laticauda. These are not common and appear often to be in a detrimental state when encountered: see Robb for details. Jewell does not mention L. laticauda in his guide.
The best known reptile species of New Zealand is undoubtedly the tuatara, Sphenodon (now in fact recognised as two closely related species). Tuataras are the last survivors of the so-called "beakheads" (Rhynchocephalia), a prehistoric reptilian group going back to the Mesozoic Age, about 200 million years. These slow-moving and long-lived creatures did undoubtedly benefit from New Zealand's isolation until the human era. Today they are confined to islands that have been cleared of rats and other mammalian predators.
The predominant reptile fauna of the islands are however lizards of the gecko and skink families. The geckos are all members of the Diplodactylinae whose relatives are found in neighbouring New Caledonia and Australia. Again, all are ovoviparous and many are active during the day. This, and their tolerance of cooler temperatures than many of their relatives, makes them unique. New Zealand's geckos belong to the genera Hoplodactylus and Naultinus, although Jewell also tentatively described Genus A and Genus B, and the genus Woodworthia has also been proposed, although this does not seem to have found acceptance yet. The skinks until recently were all considered members of the huge Australo-Pacific genus Leiolopisma. This latter has now been broken up somewhat, and the New Zealand endemic skinks allocated to the genera Cyclodina and Oligosoma. Of these, Oligosoma is the larger and more widespread. All however have suffered from the introduction of mammalian predators to the islands, and some, especially Cyclodina, are now confined to mammal-free islands off the coast of New Zealand, especially in North Island. The skinks show some interesting characteristics. All but one are ovoviparous (admittedly not unique in skinks, but a very predominant tendency in New Zealand), some are omnivorous, consuming berries as well as insects, and some are associated with coastline habitat, although this tendency is also found in skinks such as Cryptoblepharus and Emoia. Some live in association with seabird colonies, foraging around nests and burrows. Of more surprise is the choice of some Oligosoma skinks of alpine habitat, a few being even found in areas of partial snow, while others forage in pools and water on the coastline, even diving. These are not true marine lizards to the degree that the marine iguana Amblyrhynchus is, but their tolerance to what must be cool temperatures on the South Island coast is quite remarkable.
More recently, a study on New Zealand's skinks using molecular and nuclear DNA concluded that all the endemic species belonged to a monophyletic (ie one common ancestor) group, and that therefore the most sensible decision from a classification point of view was to group them all into a single genus. For this reason Cyclodina has now been merged with Oligosoma. Dr Geoff Patterson kindly sent me a copy of this paper in January 2010.
In addition to chelonians, a number of non-native lizards found their way to New Zealand over the years, but it appears only the Australian skink Lampropholis delicata has become established, in upper North Island. The geckos Cnemaspis kendalli, Gehyra mutilata and Hemidactylus garnotii (the latter two being well-known travellers) have also variously been reported from New Zealand but do not appear to have become established.
Off the coast of North and South Island are several smaller islands which over the recent past have become sanctuaries for bird-, reptile- and frog life, having been systematically cleared of cats, rats and other mammalian predators. The principal islands in terms of herpetofauna are as follows:
The Kermadec Islands are 800-1000km northeast of North Island and a similar distance from Tonga. Interestingly, given the amount of inter-island rafting that has carried skinks in particular around the Pacific, there are no land reptile species on the islands, although sea turtles and sea snakes are found in the marine reserve.
Further afield and perhaps less pertinent to the herpetofauna of New Zealand proper, the Cook Islands are a self-governing dependency of New Zealand in the Pacific. They are home to three species of Emoia skinks (adspersa, cyanura and trossula) plus the larger skink Lygosoma bowringii, the diminutive Flowerpot Snake Ramphotyphlops braminus and the colubrid wolf snake Lycodon capucinus, and are visited by Chelonia mydas and Eretmochelys imbricata. None of these species or their genera are found on New Zealand or offshore islands (other than the sea turtles when occasionally passing through) and are more representative of the herpetofauna of the Pacific, especially Emoia which are noted migrants around the area.
The sub-Antarctic island possessions of New Zealand are, as one might expect, devoid of reptile and amphibian fauna.
This short essay derives from a few print sources and several online articles and pages (see below): any mistakes are my own. The aim of this essay is to raise awareness of New Zealand's native reptile and amphibian fauna among both local people and visitors. It seems to me that in the past the islands have been associated mainly with unique ferns and flightless birds, though the tuatara has now become known as a national symbol. Those of us interested in herpetology have long been fascinated by neighbouring Australia and New Caledonia but have read comparatively little on New Zealand, partly because books on its herpetofauna have until recently not been widely available for some reason. The last thing I intend is for this essay to produce an unhealthy interest in unscrupulous people in smuggling native animals out of the country. I have made my own criticisms of excessive wildlife laws elsewhere, but many of New Zealand's native reptiles and frogs are endangered and to smuggle them is not only illegal but highly immoral and would appear to produce no real gain for conservation. Limited legal commercial breeding of selected species, or giving individuals to reputable zoos around the world as has been done with the tuatara, would appear to offer a constructive way forward.
The tuatara, lizards and frogs of New Zealand, Richard Sharell, William Collins, Auckland 1975. Taxonomy now rather outdated, and with fairly general details on a selection of the principal reptiles and amphibians, but still useful, and also has a section on Sphenodon and its place in Maori culture. The 1975 edition contains an addendum on Leiolopisma suteri (now Oligosoma suteri).
New Zealand Reptiles and Amphibians, Joan Robb, William Collins, Auckland 1980. All native skinks herein are assigned to Leiolopisma, but the book still gives handy details and very useful maps.
A Photographic Guide to Reptiles & Amphibians of New Zealand, Tony Jewell, New Holland 2008. Handy pocket-sized field guide to the country's herpetology.
"Origin, diversification and systematics of the New Zealand skink fauna (Reptilia: Scincidae)", D G Chapple, P A Ritchie, C H Daugherty, Molecular Phylogenetics and Evolution 52: 470-487, 2009.
I have not read the following so cannot comment on them, but these may also be useful for further reading:
New Zealand Frogs and Reptiles, Brian Gill and Tony Whitaker, Bateman Field Guide 2001.
New Zealand Lizards: An Annotated Bibliography, Tony Whitaker and Bruce Thomas, New Zealand Department of Scientific and Industrial Research, 1989.
Wikipedia article on Geology of New Zealand
Wikipedia Timeline of the Environmental History of New Zealand
NZ government article on the historic acclimatisation process
New Zealand Herpetological Society
"A note on the lizards of the Slipper Island Group", D R Towns, 1974.
"Reptiles of Cuvier Island", J MacCallum and F R Harker, 1982.
Article on the release of Auckland Zoo-bred tuataras of Cuvier Island origin back to their home island.
"The Lizards of Whale Island", D R Towns, 1979.
New Zealand Department of Conservation article on Offshore Islands and Conservation
Electronic atlas of New Zealand reptiles and amphibians
Coupled with the above, a helpful comparison of the names used by Jewell's guides with those used in the electronic atlas, since Jewell's nomenclature has not been accepted by all authorities
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