Geckos are small lizards known for their ability to cling to vertical surfaces. They have specialized toe pads that allow them to adhere using intermolecular forces. There are over 1,500 described species of geckos found in warm climates throughout the world. Most geckos have colors like brown, grey, green, or tan that help them camouflage in their environments. However, some rare species exhibit brilliant blue coloration. In this article, we will explore the phenomenon of blue geckos and just how rare they are.
What causes blue coloration in geckos?
The vibrant blue hue found in certain gecko species is not caused by pigmentation like many other lizard colors, but is instead a structural color. Under an electron microscope, specialized stacked plates in the gecko’s skin cells scatter light to reflect blue wavelengths. This is called iridophore structural coloration. Iridophores contain guanine crystals that interact with light through diffraction, interference, and scattering to produce the bright blue tones. This phenomenon is similar to what makes Morpho butterflies or peacock feathers appear blue.
Blue gecko species
There are a handful of gecko species that exhibit blue coloration thanks to iridophores:
| Blue-tailed day gecko | Phelsuma laticauda |
| Blue-tailed mole skink | Eroticoscincus graciloides |
| Helmeted gecko | Tarentola chazaliae |
| Peacock day gecko | Phelsuma quadriocellata |
Of these, the blue-tailed day gecko is the most vividly and extensively blue. The blue-tailed mole skink and helmeted gecko have blue tails, while the rest of their bodies are more drably colored. The peacock day gecko has blue spots and patterns on a green background.
Blue-tailed day gecko
The blue-tailed day gecko (Phelsuma laticauda) displays the most brilliant blue coloration of any gecko species. It is native to Madagascar and the nearby Comoro Islands. These lizards reach lengths of 8-10 inches from snout to tail tip. Their bodies are a vibrant turquoise or azure blue, while their tails become more purple-blue. The undersides are whitish or pale blue. They have large yellow eyes with round black pupils.
These arboreal geckos inhabit tropical forests and are adept climbers. They are diurnal, active during the day when their bright colors stand out. The blue-tailed day gecko feeds on insects, nectar, pollen, and tree sap.
This species is popular in the exotic pet trade due to its stunning looks. They do well in captivity with proper care.
Rarity of blue geckos
Of the over 1,500 gecko species, only 4 are known to have blue individuals. That puts blue geckos in the top 0.3% rarest gecko color morphs. The blue tails and markings are an anomaly from the usual gecko patterning.
Within the blue-tailed day gecko species, the intensity of blue can vary based on location. Some populations on small islands in the Comoros exhibit a deeper, more vivid blue than those on Madagascar. This may be due to founder effects and limited gene pools amplifying the blue genes.
Population and conservation status
The International Union for Conservation of Nature (IUCN) Red List categorizes the blue-tailed day gecko as Least Concern. This means it is not currently vulnerable to extinction. The total population is likely greater than 100,000 mature individuals and remains widespread through its native range.
However, in the 1990s large numbers of blue-tailed day geckos were exported for the pet trade. This may have caused some population declines in localized areas. Currently, capture quotas and export limits try to control the pet trade impacts. Habitat loss due to deforestation also risks the restricted island populations most.
Herpetoculturists have bred captive populations of different color morphs, including “super blue” geckos. These help supply pet demand without large impacts on wild populations.
Other rare blue reptiles
Blue coloration is highly unusual in reptiles. Beyond the few gecko species, some other examples of rare blue reptiles include:
| Blue iguana | Cyclura lewisi |
| Blue-throated keeled lizard | Gastropholis prasina |
| Solomon Island prehensile-tailed skink | Corucia zebrata |
| Malayan coral snake | Calliophis bivirgatus |
Like the blue geckos, these species display blue skin pigmentation as juveniles and lose some of the brilliance as they mature. The vibrant coloration may serve as an aposematic warning signal to potential predators. Herpetologists still have more to learn about the functional significance of blue tones in reptiles.
Significance of blue color vision in geckos
One hypothesis for the evolution of blue skin in geckos is related to their blue color vision. Most geckos have tetrachromatic vision encompassing ultraviolet, blue, green, and red light reception. Their eyes contain four types of cone cells with different opsins sensitive to various wavelengths.
This expanded color vision gives geckos an extra channel for visual communication compared to humans. The iridophore blue skin may be tuned to the gecko visual system, allowing members of a species to signal to each other in the blue channel. More research is needed on gecko visual systems and how they make use of blue coloration.
Conclusion
Blue is an exceptionally rare color for reptiles to exhibit. Of all the gecko species, only 4 are known to have blue individuals. The blue-tailed day gecko shows the most extensive and brilliant blue hues. A few other lizard species demonstrate blue tones just on certain body parts like the tail or throat.
Structural coloration from stacked iridophore cells in the dermis layer of skin produces the dazzling blue appearance. These geckos likely utilize the blue hues as social signals to other members of their species. Their advanced color vision allows them to see wavelengths humans cannot.
Overall, blue geckos remain one of the most colorful and visually striking anomalies in the reptile world. As herpetologists learn more about their genetics, evolution, and neurobiology, we continue unraveling nature’s mysteries around this rare phenomenon.
