The Canterbury gecko (Woodworthia brunnea) is a gecko found in the South Island of New Zealand. It is also known by the Māori names Waitaha gecko and Moko-pāpā, and as the brown gecko. It had previously been placed in a different genus and called Hoplodactylus brunneus, but further study split the genus Hoplodactylus into six genera, with some groups close to the former Hoplodactylus maculatus "Canterbury" being assigned to the new genus Woodworthia.
The forms are separated geographically but have evolved from a common ancestor. Woodworthia geckos belong to the subfamily Diplodactylidae, known to be a primitive group found only in Australia, New Caledonia and New Zealand. The significant differences between New Zealand and Australian Diplodactylids may suggest that geckos have been in New Zealand since it broke away from the Gondwana supercontinent 85 million years ago. The geckos are usually brown and highly patterned, including striped morphs. The eye colour ranges from green, brown to bright yellow and they can occur over a variety of habitats including dune-lands, forests, shrublands, river terraces and bluffs. The gecko is endemic to New Zealand.
Species description and identification
Geckos are specialised lizards, with large eyes that are permanently open, and large fleshy tongues that are used to clean the eyes and scales of the lips. They have "broad scale-like plates on the lower surfaces of their toes which employ millions of microscopic setae (hair-like structures), each with an attracting magnetic force" that gives adhesion to smooth surfaces. Woodworthia gecko species are often darker in colour than other New Zealand gecko species. Canterbury geckos are usually brown, grey or olive with pale bands, blotches or stripes that are bright, and large blackish patches (often on the intact tail).
The eye colour varies from green to brown to bright yellow and they usually have a narrow or broad pale stripe running from eye to nostril. The rostral scale contacts or virtually touches the nostril. Their undersides are usually pale and uniform in colour, although a few individuals have been observed with spotted bellies. They have pink mouths with a pink tongue that is tipped with grey. It has been observed that specimens from coastal dune habitats are smaller than those from forest/rocky habitats, measuring around between snout and vent, as opposed to . Their tail length is usually the same as snout-vent length when intact. Canterbury gecko toes have "9-12 lamellae" and straight distal phalanges, while the soles of their feet are usually light grey. They can be highly variable in colour and patterning which may explain the difficulties in classifying them as their own species in earlier years.
Geographic distribution and habitat
Canterbury gecko are a species endemic to the South Island of New Zealand, from southern Marlborough to mid-Canterbury and the Banks Peninsula. They are also found inland in the Canterbury plains and on coastal hills south to around the Rakaia River. They have been observed on Kaitorete spit in their smaller dune-land size. Around the Banks Peninsula and the Port Hills, they are locally abundant but have been lost in many parts of the Canterbury plains due to habitat loss/land use change.
The Canterbury gecko has a range of habitat preferences primarily in lowland areas which include trees in forests as they retreat to sites beneath loose bark or in deep hallows especially in standing dead trees. They also live in creviced rock outcrops, rock tumbles, bluffs and associated scrubby vegetation as well as dune lands among driftwood, scrub, rocks and pohuehue, and along coastlines, especially Birdlings Flat/Kaitorete Spit.
The climate around the Banks Peninsula consists of an average rainfall of around per year, as the rainfall in New Zealand varies quite a bit we can see that the geckos prefer the East Coast compared to the West Coast as it is a lot drier on the East. The average temperature ranges from a high of 23 degrees to a low of 4 degrees in summer and a high of 13 degrees to a low of 2 degrees in winter. Canterbury has around 2100–2300 hours of sunshine annually. The Canterbury gecko exhibits high site fidelity and has very small home range. They have also adapted to widespread habitat modifications and can be seen in shelterbelts and other wild areas in the agricultural landscape.
Canterbury geckos are a generalist/facultative species, as they inhabit the coastal, lowland, and montane/subalpine regions of the South Island, in a wide variety of habitats. They are restricted below the tree line in most areas. On predator-free islands, they have been found inhabiting seabird burrows and can be found frequently in modified environments such as inorganic debris and buildings, close to human habitation. Small-leaved coprosmas are a favourite of New Zealand lizard species, as they offer a protective habitat in their tangled branches. Pohuehue (Muehlenbeckia complexa) is another favourite, as many invertebrates are found on it, and the fruit is ideal for lizards.
The New Zealand Department of Conservation has them listed as "bio status category: Indigenous (Endemic)", with a New Zealand threat classification of declining.
Life cycle/phenology
Among New Zealand species of geckos and skinks, females will typically mate and begin vitellogenesis in autumn, storing the sperm over winter and ovulating in the spring. The pregnancy usually lasts around three months, although gestation length may reach 14 months as it is temperature dependent. This quality is especially the case for nocturnally foraging species such as the Canterbury gecko Cree & Hare state in 'New Zealand Lizards' that "male geckos and skinks exhibit spermiogenesis during summer and/or autumn, with prolonged or continuous spermatocytogenesis and no period of complete testicular regression." Lizards in cool climates in South America and Tasmania exhibit similar features to the New Zealand species, such as "autumn mating with prolonged vitellogenesis, [the] possibility of a secondary mating season in spring, prolonged pregnancies with sometimes less-than-annual reproduction in females". Native geckos (and skinks) reach sexual maturity and start to reproduce around three years of age, with variations according to species and condition. The main determining factor in the ability to mate appears to be size. There have been cases of geckos in captivity that have mated and produced viable progeny at two years of age, although their first birth is often one hatchling rather than the norm of two.
Canterbury geckos are primarily nocturnal but have been known to sun bake at the entrance to their retreats. They often form large social aggregations, especially in areas without predators where they are abundant in numbers. The Canterbury gecko is known to have the highest recorded longevity of any New Zealand gecko species, at 53 years of age in the wild. Young are born in late February to March, with females often giving birth to a maximum litter of two. They are viviparous, meaning the eggs hatch in the female's oviduct before the young are born - "Vivipary is thought to be an adaptation to New Zealand's cooling climate during the ice ages – most other viviparous lizards occur in colder regions of the world". They mate once a year, usually in spring or summer. "Geckos are very responsive to the influence of temperature and in cooler climates will draw out the reproductive cycle", with females sometimes producing a litter every second or third year instead of every year. They are thermoregulators, basking in the sun either directly or through a thin cover object, and many New Zealand geckos and frogs can lighten or darken their colouration to enable the absorption of thermal energy.
Diet
Most New Zealand native lizard species, including Canterbury geckos, are omnivorous, eating a range of arthropods and sometimes other lizards and berries, and nectar and pollen from flowers. Canterbury geckos are primarily insectivores (e.g. eating moths and flies) but will also feed on fruit (berries), in particular from the Coprosma spp. New Zealand gecko species are known to drink nectar from many native plants such as cabbage trees, flax, southern rātā and pōhutukawa, and likely play a minor role in the pollination of these species. Divaricating plant species such as mingimingi (Coprosma propinqua) produce small black/blue berries that are a favourite of lizards. In the paper 'The role of lizards as seed dispersers in New Zealand' it was suggested that New Zealand lizards are "effective dispersers, and white-blue fruits and divaricating shrubs are adapted to lizard dispersal". It was found that lizards eat the fruits of around 23 native species, of which five are divaricating, and favour white-blue fruits to red, even though these are less present in the flora. White-blue fruits are often found in open habitats, which can be near the rocky habitat of the Canterbury gecko. It was also discovered that "Seeds in lizard scats have germination percentages≤control seeds in four species tested. Lizards generally disperse seeds <, but allow seeds to escape parent plants and reach safe establishment sites." The researchers concluded that lizards may be important seed dispersers even at their low numbers on the mainland, and potentially assist in the dispersal of more seeds than previously thought: "In shrublands lacking frugivorous birds, lizards may be the only remaining dispersers".
Lizard species vary their behaviour according to weather or habitat opportunities: when it is cold, they may remain inactive or employ the "sit and wait" method for food, and in warmer weather, they may roam their habitats in search of food. Hare, Pledger, Thompson, Miller, & Daugherty studied the metabolic rate of nocturnal Diplodactylidae species in New Zealand emerging for either foraging or thermoregulating through most of the day and found that "their Vo2 [rate of oxygen consumption] is usually elevated only during the active (foraging) phase. ̇Thus, many nocturnal lizards are active at suboptimal temperatures and emergent and thermoregulating when their metabolic rate is low." It was noted that as their metabolic rate would increase with the "corresponding increase in temperature from diurnal thermoregulation," that the lower metabolic rate during the day may not be significant to their physiology.
Predator/prey
Canterbury geckos in the wild have been recorded as having low levels of red mites. All New Zealand geckos have two main threats which are predation and habitat destruction. The main predators of the Canterbury gecko include mammalian pests such as mice, rats, weasels, hedgehogs, cats, stoats, ferrets, pigs and possums. With the evolving suburban areas in Canterbury, the geckos are being pushed out of their natural habitat and with conversion by burning and ploughing, this is threatening geckos that live in rock outcrops.
Introduced mammals represent one of the biggest threats to many of New Zealand's native species, including the Canterbury gecko. Birds and lizards filled the role of land mammals in New Zealand before the arrival of humans, and due to the absence of these predatory mammals, many species are somewhat naïve to the dangers of predators. Native lizards are predated on by cats, mustelids, possums, hedgehogs and rats (both the European rats and the Polynesian kiore). Some lizards on the mainland and smaller islands went extinct after the introduction of kiore, and many more after the arrival of the various European predators. The Department of Conservation has estimated that New Zealand's population of 1.4 million domestic cats kill "at least 18.76 million animals a year, including 1.12 million native birds".