Geckos, Cryptic Creatures
Written by Freya Bacon-Bootham
Aotearoa is known for having a large diversity of manu/birds; however, it is also the land of the mokomoko/lizards. The most species-rich group of mokomoko worldwide are geckos – who are fascinating and cryptic creatures. Of Aotearoa’s native land vertebrate species, 50% are mokomoko. Within these mokomoko, there are 48 known species of geckos.
Geckos can be identified by their broad head, rounded snouts, defined necks, and skin that looks loose and rough. They have no eyelids; instead, there is a clear scale in front of their eye, which they lick to keep moist and clean. As omnivores, geckos are a key part of native plant life, spreading pollen when drinking their nectar and seeds after eating fruit.
At Zealandia Te Māra a Tāne, at there are two species of geckos and another three possibly present. Geckos are cryptic and inconspicuous, making it difficult to know for certain how many are in the sanctuary despite the conservation team carrying out surveys. However, these surveys have found ngahere and raukawa geckos in the sanctuary.
If you’ve spotted a gecko at Zealandia Te Māra a Tāne and are trying to figure out which species it is, ngahere and raukawa geckos have some distinct differences. Ngahere geckos are local to Whanganui-a-Tara/Wellington. They are light grey-dark brown with rows of V or W-shaped blotches along their backs and a bright orange mouth and tongue. Raukawa geckos are common across the North Island and are normally found on the ground. They are grey/brown with irregular markings, and their mouth and tongue are pink.
There is a possibility that barking geckos are in Zealandia Te Māra a Tāne, although they have yet to be found. They are a tricky species to spot as they live high in the canopy of trees and have excellent camouflage. The pacific and gold stripe geckos are also local to Te Whanganui-a-Tara but have not been seen inside the sanctuary yet. We don’t know all the species that are inside the fence, as mokomoko can move in and out of the sanctuary by themselves.
The geckos in Aotearoa are very long-lived, with some living up to 40 years old, compared to the two years of a tropical gecko. Due to living long lives, geckos in Aotearoa are slow breeders who don’t mature till they’re a few years old. They give birth to live young, an adaptation that improves survival by protecting their young from cold temperatures during development. It has also been found that birth can be delayed until temperatures improve.
Two intriguing parts of gecko anatomy are their tails and feet.
Geckos have fascinating sticky feet that have inspired many inventions worldwide. They can walk along any angle and even upside down, all because of them.
A gecko’s foot is bulbous and covered in lamellae, which are skin folds. Each lamella is covered in hundreds of tiny hairs called setae. These setae are made from stiff keratin, the same material that makes up human nails and hair. They branch off at slanting, nearly horizontal angles and split into hundreds of tiny hairs called spatulae. Having hundreds of hairs increases the surface area the gecko has to stick to a surface, allowing them to support more weight.
Credit: Janice McKenna
Geckos’ sticky feet are made possible because of what is called ‘Van der Waals force’. Van der Waals force is very weak bonding between the atoms of the gecko’s feet and what they are sticking to. It occurs because the atoms get close enough to each other to act like magnets. Utilising this weak force allows geckos to climb sheer surfaces and walk upside down but still be able to move quickly.
Credit: Janice McKenna
Geckos also have the ability to make their tails drop off – this skill is called caudal autonomy. This is a talent they use to thwart predation attacks, leaving their tail behind to distract the predator while they run off and hide. Along the gecko’s original tail, multiple spots are designated as breaking points, allowing the tail to drop off without causing pain. Once the gecko has lost part of its tail this will regrow but using different materials than the original. The regrown tail is obvious compared to the old one. Visually, the new tail will often be shorter, have different skin colouring and sometimes may grow back forked. Internally this tail is also different; instead of the new tail growing with a spinal cord, it grows from cartilage. Cartilage provides structure to the new tail and means it can’t break off along the regrown tail again. Sometimes scientists use the difference between the tails as a crude measure of how heavy predator pressure is.
Geckos are cryptic, inconspicuous, and fascinating mokomoko. See if you can spot them around Zealandia Te Māra a Tāne and watch their interesting bodies in action. To help out geckos at home, you can create habitats for them to thrive. They need places to hide with lots of crevices; you can create this by having loose rocks and branches and planting native dense spreading shrubs like coprosma. Geckos are also threatened by predation, so ensuring your gecko habitat is safe from cats, rats, and mice will keep any visiting geckos safe.