Gecko

Geckos are a diverse group of small, mostly carnivorous lizards belonging to the suborder Gekkota. They are found in warm climates on every continent except for Antarctica. With approximately 1,500 different species worldwide, they represent the most species-rich group of lizards on Earth.

Geckos are unique among lizards because of their vocalizations. While many lizards are silent, most geckos in the family Gekkonidae use chirping or clicking sounds to interact socially. For example, the Tokay gecko is famous for its loud mating calls. Some species may also hiss when they feel threatened or alarmed.

Most geckos have highly specialized eyes designed for life in the dark. Because they are usually nocturnal, they have evolved excellent night vision. In fact, their color vision in low light is 350 times more sensitive than human eyes. Most geckos lack eyelids, which means they cannot blink to clear their eyes. Instead, they possess a transparent membrane called a brille that covers the outer surface of the eyeball. To keep this membrane clean and moist, these geckos often lick their own eyes.

Their eyes also feature a fixed lens that enlarges in the darkness to capture more light.

One of the most remarkable features of many geckos is their ability to climb smooth and vertical surfaces. About 60% of gecko species possess adhesive toe pads that allow them to walk on ceilings. This ability is not caused by liquids or surface tension. Instead, it involves microscopic structures on their feet. Each square millimeter of a footpad contains about 14,000 hair-like structures called setae. Each seta is only 5 micrometers in diameter, which is much thinner than a human hair. At the tip of each seta are even smaller structures called spatulae.

These spatulae are only 0.2 micrometers long. Scientists believe these structures interact with surfaces through electrostatic interaction, which is caused by contact electrification. This allows them to grip surfaces without needing any fluids.

To move efficiently, geckos use a process called digital hyperextension. While it might look like they have double-jointed toes, they are actually using this specialized movement to peel their toes off surfaces. They start at the tips and peel inward, much like how you might remove a piece of Scotch Tape. This peeling action ensures that they only need a small amount of force to separate each individual spatula from the surface. To help with this, geckos produce fatty substances called phospholipids. These lipids act as a lubricant, allowing the gecko to detach its foot quickly before taking the next step.

Geckos are ectothermic, meaning they produce very little metabolic heat. Their body temperature depends almost entirely on the temperature of their environment. To perform basic functions like eating, moving, or reproducing, they must maintain an elevated body temperature. This biological need is also linked to their skin, which they must shed at regular intervals. This process is known as molting. For young geckos, shedding can happen as often as once a week. As they grow into adults, they typically shed every one to two months.

Some species, like the leopard gecko, may shed every two to four weeks. To speed up the process, geckos will sometimes detach loose skin and eat it.

We can trace the history of these creatures through the fossil record. Some early relatives, such as the arboreal Eichstaettisaurus from the late Jurassic of Germany, are well-documented. The oldest fossils of modern geckos date back about 100 million years to the mid-Cretaceous period. These fossils, found in Burmese amber in Myanmar, show that geckos already possessed adhesive pads similar to those we see today.

This shows that their incredible climbing abilities have been part of their biology for millions of years.

The diversity of geckos is reflected in their extreme sizes and specialized lifestyles. The Jaragua sphaero is a tiny species discovered in 2001 on an island near Hispaniola. In contrast, the largest known species, Gigarcanum delcourti, is known only from a single specimen collected in the 19th century. This large gecko likely lived in the native forests of New Caledonia.

Many species have also developed unique survival traits, such as the mossy leaf-tailed gecko. This species uses camouflage to look like tree bark, including lichens and moss. It even has dermal flaps of skin to scatter shadows and hide its outline from predators.