Naultinus is a genus of geckos that are endemic to New Zealand. On account of their striking colouration, species in the genus Naultinus are commonly known as green geckos. There are nine described species in the genus. Species in the genus share a number of traits that set them apart as quite different from the rest of the world's two thousand odd gecko species, which are generally brown in colour, ovivaparous, short-lived and nocturnal. In contrast, Naultinus are green (with the exceptions of males in two South Island species which exhibit sexual dimorphism in colouration), ovovivaparous, live up to 30 years or more and are strictly diurnal. New Zealand has a temperate, maritime climate, and in terms of distribution Naultinus is one of the southernmost gecko genera in the world — some species live in habitats in the South Island which receive regular snowfall in winter. Animals in this genus possess several physiological and behavioural adaptations to cope with these periods of low temperatures and adverse weather.
While historically widespread and quite common in areas of native forest all over the country, all species in this genus are of conservation concern in the present day. All nine species of Naultinus are declining in the wild and are much harder to find than they used to be; the populations of the various species are fragmented and approaching extinction, while others in the genus have already gone extinct. Entire populations of certain species, with unique traits and distinctive genetic profiles, have disappeared in the last 20 years. The primary known agents of this catastrophic decline include predation by invasive mammalian and avian species, habitat destruction and poaching for the illegal pet trade. Vespid wasp predation is speculated to be another possible contributing cause. Legal protection in the form of longer prison sentences for poachers caught with New Zealand protected species has been increased in recent years and translocations of various species to pest free islands have been undertaken with mixed results, but the task of saving these animals remains daunting. The behavioural and visually cryptic nature of these animals also pose challenges to their conservation management. The genus is, in general, in "dire need of research, particularly into factors that are causing their apparent decline", certain aspects of which remain unexplained.
Taxonomy
The following nine described species are recognized as being valid. A binomial authority in parentheses indicates that the species was originally described in a genus other than Naultinus.
- Naultinus elegans – Auckland green gecko
- Naultinus flavirictus <small>Hitchough, Nielsen, Lysaght, & Bauer, 2021</small> – Aupouri green gecko, North Cape green gecko, yellow-lipped green gecko
- Naultinus gemmeus – jewelled gecko
- Naultinus grayii – Northland green gecko, Gray's tree gecko
- Naultinus manukanus – Marlborough green gecko, northern tree gecko
- Naultinus punctatus – Wellington green gecko
- Naultinus rudis – rough gecko, natural tree gecko
- Naultinus stellatus – Nelson green gecko, starry tree gecko
- Naultinus tuberculatus – West Coast green gecko, Lewis Pass green gecko
Defining what constitutes a species among different populations within this genus has proved difficult and is still a matter of some scientific debate. Genetic evidence suggests that all nine species share an ancestor which is "very recent" in deep time terms and that hybridization between them is quite common. All species will interbreed in the wild, which has led some biologists to reject the notion of multiple Naultinus species and to instead view each "species" as a separate "race" or subspecies of a single, widespread species of this genus. However, there are a number of clear differences between recognized species in colouration, breeding times and even scale morphology. Multiple neighbouring species have slightly different mating seasons and behaviour, which is thought to explain why the species maintain their differences despite "strong reproductive compatibility". These differences are the basis for the present consensus in the scientific community that Nautilnus is constituted of nine species instead of nine races of a single species.
{| class="wikitable"
|-
! Hoplodactylus !! Naultinus
|-
| Mainly grey-brown || Mainly green
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| Nocturnal || Diurnal
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| Terrestrial, sometimes on tree trunks || Arboreal, on foliage
|-
| Active-prey-searching || Sit-and-wait predator
|-
| Generally fast-moving|| Generally slow-moving
|-
| Can change intensity of skin colour || Skin colour intensity cannot be changed
|-
| Wide, non-prehensile tails, readily shed || Narrow, tapering prehensile tails, reluctantly shed
|-
| Some have wider toe pads with claws, adapted for climbing smooth, vertical surfaces || Thin toe pads adapted for grasping twigs and foliage
|}
Distribution and habitat
The nine described species of Naultinus are found throughout the North and South islands of New Zealand and on a number of offshore islands. Historically, Naultinus species lived throughout the length of New Zealand, from the coast to as much as 1400 metres above sea level. However, all species have now undergone massive declines, and populations nationwide are fragmented and few (see "Conservation") Four species; elegans, grayii, flavirictus and punctatus are found only in the North Island. What was previously thought to be a distinct population of grayii, found only in the far north on the Aupōuri Peninsula has been determined from genetic work in the early 2000s to be a new species, more closely related, in fact, to elegans.
None of the Naultinus gecko populations are sympatric, presumably because each species is finely adapted to its local environment and also because their respective ecological niches are incredibly similar.
Behaviour and ecology
Activity patterns and diet
Most of the world's two thousand-odd species of geckos are active by night (nocturnal) whereas all species of Naultinus are active by day (diurnal). All New Zealand geckos will supplement their primarily insectivorous diet and consume nectar and berries (the small purple fruits of Māhoe for example) and there is evidence that, in doing so, they may have a function in New Zealand ecosystems as pollinators and seed dispersers for certain species of native plant. All four North Island Naultinus species will exhibit "gaping" behaviour when threatened but in addition grayi and punctatus will lunge aggressively at the potential predator in question, often barking as they do so. Elegans, grayii and punctatus can all be kept on an "A permit", which is the entry level license given to new keepers, while the remaining species in the genus require a "B permit" for which several years experience keeping geckos is required. In the past, animals could be collected from the wild to add to captive collections and this is how people typically used to enter the hobby;
Naultinus are also kept in captivity by enthusiasts in overseas countries but it should be stressed that trade is incredibly difficult, and one must obtain adequate CITES permits for importation and exportation. This process is regulated by the CITES Management Authority, which ascertains whether or not founding stock were obtained by a keeper in a particular country prior to 1981. This is often quite difficult, and usually prohibitive of international trade between Europe (where most stock resides outside of New Zealand) and other countries.
Threats and decline
Collectively, the species of genus Naultinus have a wide range over most of New Zealand's land area and yet all of them are now increasingly rare and hard to find. This is in stark contrast to anecdotal reports among NZ herpetoculturalists who found them abundant in suitable habitat (such as regenerating bush in the Marlborough Sounds) in the 1960s from which they have now all but vanished. The three major factors thought to be responsible for this decline are; habitat destruction, predation by introduced mammalian species and poaching for the illegal pet trade.
Barking geckos were common in shrublands all around the Wellington region up until the 1960s and 1970s and the Convention on International Trade in Endangered Species (CITES). In an effort to clamp down on continual poaching, DOC attempted to get tighter controls placed on trade in Naultinus in 2002 under the CITES agreement but the request was denied, The Judge for the case, Judge Raoul Neave commented that "a significant increase in the sentencing could be desirable" in such cases.
Conservation
There is a critical lack of scientific research that has been done on Naultinus species and this fact, combined with the behaviourally and visually cryptic nature of the genus pose major challenges to their conservation management. For multiple Naultinus species, (examples include grayii,stellatus and rudis) there is a complete lack of accurate data in key areas such as distribution, abundance and recruitment rate (primarily because they are visually and behaviourally cryptic)- these types of information are critical to developing conservation management plans and make the conservation status of these species difficult to determine;