Geckos

Geckos are the most species rich group of lizards worldwide, with a series of common traits found in almost all species. These traits include: a transparent scale in the place of eyelids (which they lick to keep clean – skinks blink, geckos can’t blink); excellent night vision in nocturnal species; the ability to self amputate their tails (autotomy); the ability to adhere to most surfaces; a loose or ‘saggy’ skin (compared to the tight smooth skin of skinks); small granular body scales, and an excellent sense of smell, sight, & hearing.

Geckos are renowned for their ability to climb vertical structures; their toes have millions of microscopic hairs called setae which create a special bond called van der waals force, allowing them to adhere to smooth surfaces. Read more about van der waals force and how geckos defy gravity.

Geckos can self amputate their tails as an escape mechanism, a process called caudal autotomy. Geckos will shed their tail to escape the grasp of a predator, before attempting a getaway as the predator is distracted by the still wriggling detached tail. As the tail is a major fat storage organ for geckos individuals may return to attempt to consume the dropped tail once the threat has passed. The new tail is always shorter than the original and contains cartilage instead of bone, with the skin of a regenerating tail differing in texture and appearance from that of the original tail. In some cases the new tail will grow back forked. Here’s a link to a great video explaining autotomy.

Geckos are ectothermic, relying on environmental heat sources to generate energy. ‘Sunbathing’ is a common behaviour in our native reptiles, either individually or in groups. All geckos shed their skin at intervals to accommodate growth, with shed skin coming off either in strips or whole.

Most species of New Zealand gecko are vocal, communicating by clicks & squeaks. When acting aggressively they arch their backs, open their mouths in a threatening manner (mouth gaping), & flick their tails from side to side.

All New Zealand geckos are ovoviviparous, a rare reproductive strategy whereby embryos develop inside eggs which are retained in the mother who then gives birth to live young. Ovoviviparity allows the mother to behaviourally manipulate their body temperature (e.g. sunbathing) to control incubation temperature, with incubation temperatures influencing the sex of offspring. New Zealand geckos generally give birth to twins in summer.

New Zealand geckos exhibit a high level of morphological conservatism (in simple terms, different species and subspecies can have very similar appearances), which can make identification of species difficult. With the advent of DNA technology, genetic studies have focussed on resolving the phylogenetic (evolutionary) relationships of New Zealand’s gecko taxa. As a result there are currently 9 described species of Naultinus (green geckos), and 11 other described species (1 extinct and 10 extant/still existing) that were formerly classified together within the Hoplodactylus genus, but have recently been split into 6 taxonomic groups (including Hoplodactylus and 5 new genera). Research continues, with a number of new, as yet unnamed taxa to be explored.

For a more in depth explanation of the taxonomic revision of New Zealand herpetofauna & current conservation classifications see:

• “Conservation status of New Zealand reptiles, 2012”
• “Dynamic taxonomy versus field identification: a dilema for New Zealand herpetologists”
• “New Zealand geckos (Diplodactylidae): Cryptic diversity in a post-Gondwanan lineage with trans-Tasman affinities”
• “A systematic revision of the New Zealand gekkonidae”