Geckos are small reptiles belonging to the lizard family Gekkonidae. These little lizards are characterized by a suite of some truly amazing features and traits, which include:
- Caudal autotomy: as a defence strategy, geckos are able to ‘drop’ their tails when seized by a predator, leaving the predator with just a tail, whilst their owners, whilst tail-less, are free to live another day. The tail eventually regenerates but interestingly it is usually a different colour and less patterned than the ‘original.’
- Oviparous: all geckos lay eggs (rather than giving birth to live young). They have very small clutch sizes, most only laying clutches of 2 eggs. Some species (or populations of a species) are actually parthenogenetic: all of the individuals are female and reproduce asexually via a mode of reproduction akin to cloning, producing genetically identical daughters.
- Small, round scales: their body surface is covered by many tiny, rounded scales. These scales are not particularly thick and so geckos are soft-bodied reptiles and lack the heavily-armoured body surface afforded by heavily keratinized scutes like those of crocodiles.
- Adhesive toe-pads: geckos have amazing climbing abilities and many of you will encounter them on vertical window panes or hanging unfazed upside-down on your ceiling. Their remarkable climbing ability owes to how a gecko’s toes bear large disc-like pads at the toe-tips. The amazing adhesive properties of the toes result from how these toe pads (also called subdigital pads or scansor pads) feature many transversely expanded rows of plate-like scales, known as scansors. Each scansor is covered with tens of thousands of microscopic projections (setae), each of which in turn bears one or more spatulate-shaped projections (spatulae). The microscopic spatuale on the tips of the setae create a very large surface area on the toes which exploit molecular attractive forces – known as Van der Waals forces – that enable them to grip to the smoothest of surfaces. This mechanism differs from that seen in tree frogs whose expanded toe pads adhesive properties result from capillary adhesion relying on a layer of liquid between the microscope cells of the toes and the substrate. Rather, in geckos this system is a dry adhesive system (doesn’t require water) with the bonding strength resulting from molecular attraction between closely associated surfaces due to changes in the distribution of electrons (the Van der Waals forces).
- Nocturnal lifestyle: almost all geckos are active during the night; during the day the escape the unwanted attention of predators and heat of the sun by hiding in crevices, burrows, under exfoliating bark, and in cracks in walls, trees or rocks. As an adaptation to their nocturnal lifestyle, geckos are characterized by very large eyes which have cat-like pupils.
- No eyelids: you’ll never see a gecko blink because they lack eye-lids! Instead the pupils are covered by clear discs that are periodically cleaned with the gecko’s tongue.
- Carnivorous: Upon emerging from their daytime retreats, geckos prey upon flying insects, but also eat other insects and spiders, and larger gecko species may consume smaller geckos and other lizards.
- Vocal: unlike many reptiles geckos have an extensive vocal repertoire, communicating frequently by emitting squeaks, buzzes, and chirps
Geckos have a cosmopolitan distribution, their range extending across the globe where suitable habitats exists. About 110 species occur in Australia. The charismatic little creature shown here, the Western Marbled Gecko (Christinus marmoratus) is endemic to southwest WA, its distribution being restricted to the cooler regions of southern parts of the state.