Naultinus gemmeus
Written by Ben Valentine (Lincoln University)
July 2005
Edited by Michael Hudson, Lincoln University, May 2006
Taxonomy
- Scientific name: Naultinus gemmeus (McCann)
- Synonyms: Heteropholis gemmeus
- Popular Common names: Jewelled Gecko.
- Other common names: Jewelled Green Gecko.
- Kingdom: Animalia
- Phylum: Chordata
- Class: Reptilia (the reptiles)
- Order: Squamata (the scaled reptiles)
- Family: Geckonidae (the geckos)
- New Zealand Status: native (endemic)
- Taxonomy sources: Cogger & Zweifel (1998), Gill & Whitaker (1996), Hudson (1994), Hutton & Drummond (1923), O’Brien (1981), Whitaker et al. (2002).
Identification
Species Description
The jewelled gecko (Naultinnus gemmeus) is a bright green lizard with white or yellow stripes or splotches that run the length of its back. But male jewelled geckos in Canterbury are unique in that they are usually brown, grey and white (Gill & Whitaker, 1996). The splotches, resembling jewels to some, are what give this gecko its name. If you see a jewelled gecko open its mouth, you will instantly notice its bright blue colour (Whitaker et al., 2002). These geckos have hazel eyes and vertical slit pupils (Rowlands 1990, Hudson 1994). Unlike some lizards, the jewelled gecko does not have the ability to change colour (Rowlands 1999).
The average jewelled gecko is 160 mm long, including its tail that accounts for almost half of its overall length (Hudson, 1994). The jewelled gecko has long clawed toes that are adapted to climbing the trees and bushes they live in.
Unlike most reptiles, which are silent, the jewelled gecko uses “chirping and chattering communication calls and a loud croak of alarm or distress” (Gill & Whitaker, 1996).
Similar species
A gecko can be distinguished from other lizards by looking at its skin and its head. A gecko’s skin appears lose and has a uniform granular texture, like a bucket of small beads. Its head will also be wider than the rest of its body, and it will have a defined neck.
To differentiate the Naultinus geckos (commonly called green geckos) from Hoplodactylus geckos, New Zealand’s other gecko genus, note the time of day they are active. Green geckos are diurnal, which means they are active during the day, while Hoplodactylus geckos are nocturnal, or active at night. As the name suggests, green geckos are generally greener than Hoplodactylus geckos, but the dull coloured male jewelled gecko in Canterbury is a notable exception (Whitaker, 1976).
If you find a green gecko on Banks Peninsula or the Otago Peninsula with splotches or stripes running down its back, it is most likely a jewelled gecko because other Naultinus geckos are much less decorated (Hayden & Morris, 1995).
Geographic Distribution
Natural and Naturalised Range
The jewelled gecko is endemic to New Zealand, which means it is the only place it occurs naturally. New Zealand is also the only place you can expect to see one in the wild, as it has not been naturalized elsewhere (DoC, 2002).
New Zealand range
Jewelled geckos live in the south-eastern part of the South Island, east of the Southern Alps and from mid- Canterbury south to Stewart Island. The most significant populations occur on Banks Peninsula near Christchurch and the Otago Peninsula near Dunedin (Whitaker et al., 2002).
Canterbury Natural Range
Although they may live elsewhere, jewelled geckos are primarily found on Banks Peninsula (Whitaker et al., 2002).
Natural History in Canterbury
Habitats
The jewelled gecko dwells in forests, shrubland, and tussock grasslands (Gill & Whitaker, 1996). Particular environments and plant species it is commonly found in are listed below:
| Area | Type | Notable Species Present |
|---|---|---|
| Forest | Montane Beech | Nothofagus species |
| Lowland Broadleaf | ||
| Shrubland | Seral | Kanuka (Kunzea ericoides) |
| Manuka (Leprospermum scoparium) | ||
| Matagouri | Discaria toumatou | |
| Subalpine | ||
| Exotic | Gorse | Gorse (Ulex europaeus) |
| Pine | Pinus sp. |
Adapted from Whitaker et al., (2002)
Jewelled geckoes have been found in shrubland as high as 1,000 metres above sea level (Whitaker et al., 2002).
Description of preferred habitats
Jewelled geckos prefer forest trees less than 2 metres high. Their slender clawed toes allow them to climb branches with ease, and their markings help them hide very well amongst the leaves (Hudson, 1994).
Phenology/Breeding
Jewelled geckos breed annually, mating in September and October and giving birth in May or June (Forster, 1970; Hayden & Morris, 1995; Rowlands, 1999). Although gestation is usually eight to nine months, studies show that geckos can delay fertilization (Rowlands, 1999).
Along with the New Caledonian rough-snouted gecko (Rhacodactylus trachyrhynchus), New Zealand Geckos (Naultinus sp. and Hoplodactylus sp.) are the only geckos in the world to give birth to live young. Researchers hypothesize this is most likely due to the need to keep developing geckos warm in the cool climate (Cogger & Zweifel, 1998). Gecko live-births aren’t exactly like mammalian live births; the baby geckos develop in the eggs which remain in the oviduct until they hatch prior to birth, known as ovoviviparity. Each litter usually consists of twin geckos, each nearly half the length of the mother at birth. The young generally remain with their parents, although no parental care is provided (Rowlands 1999).
Geckos generally reach sexual maturity after three years, although some studies believe that sexual maturity is a factor of size rather than age, and therefore is dependent on climate and food availability (Rowlands, 1999).
Longevity
The exact lifespan of the jewelled gecko is unknown, but is believed to be surprisingly long for a creature its size. Other Naultinus geckos live upwards of 20 years in captivity, and many of New Zealand’s lizards live for 10–12 years in the wild (Whitaker, 1976; Rowlands, 1999).
Diet
Jewelled geckos are insectivores. They stalk flies, beetles, and other insects very slowly before suddenly lunging and capturing their prey with their mouths. A common misconception is that geckos catch prey with their tongues, but the tongue is merely used to hold down the prey after it has been caught in a gecko’s mouth. Geckos will also eat soft fruit and berries, but hardly ever eat dead insects (Whitaker, 1976; Rowlands, 1999).
Behaviour
Because they are ectothermic (cold-blooded) and diurnal (active during the daytime), jewelled geckos regulate their body temperature by moving in and out of the shadows provided by the plants they live in (Rowlands, 1999). They are expert climbers, using their long, clawed toes and prehensile tail to get around. Their tail is strong enough to hang by, and geckos use it like another leg. Geckos can purposefully lose their tail if threatened as a means of defence, but because is so useful, they are less likely to drop it than other lizards are. The tail will regrow, but will never be as long as the original, nor have the same colour or patterning (O’Brien 1981, Gill & Whitaker 1996, DoC 2002).
Jewelled geckos shed their skin every six to eight weeks during the summer (Whitaker, 1967).
A gecko’s eyelids are always closed, but are transparent so that it can still see. When a gecko’s eyelids get dirty, it will lick them clean with its tongue (Gunson, 2004).
Predators
Prior to the introduction of new animal species by humans, only a few species of native birds ate the jewelled gecko, and only the kingfisher (Halcyon sancta) ate very many. Tuatara (Sphenodon sp.) also occasionally known to eat jewelled geckos when the two occurred in the same area.
Today the story is different; rats (Rattus spp.) are the primary threat to jewelled gecko populations, with cats (Felis silvestris), stoats and weasels (Mustela spp.) close behind. Introduced bird species, including myna ( Acridotheres sp.) and starling (Sturnidae sp.), also eat jewelled geckos (Rowlands, 1999).
Parasites
In the wild, jewelled geckos are not affected by any known parasites, but in captivity red skin mites can be a problem (Rowlands, 1999).
Abundance and Conservation Status
- New Zealand: threatened
- Canterbury: threatened
The jewelled gecko is classified as a threatened species by the Department of Conservation, with human induced gradual decline (DoC, 2002).
Loss of habitat is the largest threat to the jewelled gecko, followed by rats and other introduced predators. The majority of habitat loss is due to the clearing of forest and scrubland for agricultural purposes. Because of the slow breeding rate, gecko populations are slow to recover in regenerating forests, and sometimes never do. This attractive gecko is also appealing to the illegal pet market (Rowlands, 1999; Whitaker et al., 2002).
How to find a JEWELLED GECKO
Jewelled geckos are masters of camouflage and are very difficult to find. The best time of year to spot one is during late autumn or early winter. At this time of year, look on the ground or in low branches for pregnant females (Forster, 1970; O’Brien, 1981).
One possible sign that a jewelled gecko is in the area is its moulted skin, but this too could be difficult to spot. If you are close, the gecko may let out a “chek chek” in an attempt to scare you off (Hayden & Morris, 1995).
Significance for people
Traditional Maori significance and uses
Although there are no mentions of the jewelled gecko in particular, we know that the Maori were aware of the little creatures, and many carvings seem to represent geckos (Rowlands, 1999). The Maoris believed geckos, particularly green geckos, to be bad omens. As Sir W. Buller reports in an early 20th century account:
…this lizard, on being molested, emits a peculiar chattering sound, which the Maoris term laughing, and of which they have a wide-spread superstitious dread. The laugh of the green lizard was enough to terrify the bravest warrior, and its occult power for evil was strangely believed in by all the tribes in every part of the country. The reptile itself, whether dead or alive, was an object of universal fear among them...
(Hutton & Drummond 1923).
Modern Uses
Geckos are popular pets, and the jewelled gecko is certainly no exception. Because it is a threatened species, there is a lot of paperwork involved in owning one. Since 1981, permission must be obtained from the Department of Conservation (DoC) to possess a jewelled gecko, and the gecko itself must be acquired from an existing breeder, as it is illegal to remove one from its natural habitat. The DoC permit must be renewed every three years, and a cage inspection is part of the issuing and renewal procprocess. Records of births, deaths, and exchanges between breeders must also be kept. Nevertheless, they remain a pet that brings excitement and discovery to many intrigued owners (Rowlands 1999).
Summary
The jewelled gecko is a fascinating creature, and is unique in many ways. At first glance, its colourings and masterful camouflage amaze observers. Others are captivated by their hunting method, if they lucky enough to witness the event. Being one of very few geckos in the world to give birth to live young is nothing to scoff at either. Because their decline is human induced, it is our responsibility to protect these wonderful geckos.
References
Cogger, H.G. & Zweifel, R.G. (1998) Encyclopedia of Reptiles & Amphibians 2nd Ed. Academic Press, San Diego, USA.
Department of Conservation (2002). Threat Class Spreadsheet. Department of Conservation, Wellington, New Zealand.
Forster, R.R. & L.M. (1970). Small Land Animals of New Zealand. John McIndoe, Dunedin New Zealand.
Gill B.J. & Whitaker A.H. (1996). New Zealand Frogs and Reptiles. Bateman, Auckland New Zealand.
Gunson, D. (2004). Dave Gunson’s New Zealand Wildlife. Penguin Books, Auckland, New Zealand.
Hayden, P & Morris, R. (1995). Wild South’s Living Treasures of New Zealand. Harper Collins, Auckland NZ.
Hudson, B. (1994). Reptiles & Amphibians in New Zealand. Print Media Specialists, Auckland, New Zealand.
Hutton, F.W. (1904). Index Faunæ Novæ Zealandiæ. Dulau & Co., London, England.
Hutton, F.W. & Drummond, J. (1923). The Animals of New Zealand. 4th Edition. Whitcombe and Tombs, Auckland NZ.
Natusch, S. (1967). Animals of New Zealand. Whitcombe & Tombs Ltd, Christchurch, New Zealand.
O’Brien, C. (1981). AA Book of New Zealand Wildlife. Lansdowne Press, Auckland, New Zealand.
Rowlands, P.R.V. (1999). New Zealand Geckos: A Guide to Captive Maintenance and Breeding. Eco Print, Auckland, New Zealand.
Whitaker, A.H. (1976). New Zealand Lizards. Forest and Bird, 202, 8–11.
Whitaker, T., Tocher, M., & Blair, T. (2002). Conservation of lizards in Otago Conservancy. Department of Conservation, Auckland, New Zealand.
Search for Naultinus gemmeus in New Zealand science online
New Zealand Journal of Ecology articles containing Naultinus gemmeus.
Search NZ Royal Society journals for articles containing Naultinus gemmeus.
