Biofluorescent Reptiles - The Namib Desert Gecko
New York City feels like about as far away from the sandy silence of the Namib desert as you can possibly get. And yet here I was in the concrete jungle to meet The Namib Desert Gecko. A biofluorescent gecko that’s a leading contender to become the first reptile known to use their biofluorescence to communicate.
I was here to meet Joe, one half of the duo that run The Gecko King. An educational, conservation and breeding facility The Gecko King in Brooklyn, New York. The room was stacked wall to wall with colour, life and geckos. Terrariums towered over me as I entered to meet the reptiles. To photograph them and learn how they behave when on their own.
It was like the world’s gecko convention stuffed into one room. Tank after tank of geckos were patiently waiting for their biofluorescence to be illuminated by UV light. Rows of terrariums climbed the walls in snake-like lines, each bathed in the hum of heat lamps. A thick humidity hung in the air as tendrils of moist soil, moss and bark drifted around the room. Smelling like a forest nestled inside the belly of an industrial giant. The crackles of geckos became amplified when the lights switched off. All around me in these modern day glass boxes were creatures with ancient DNA; their ancestors having roamed the land millions of years before humans ever walked.
A roomfull of geckos
We began our evening with a Madagascan mossy leaf-tailed gecko. This gecko had a gorgeous patchwork orange biofluorescence that complimented the camouflage patterns of his skin. Next up was a Malaysian Tokay Gecko. Tokay geckos are daytime geckos that sport many colours and spots. They have bite like no other and once they can a bite in, they don’t want to let go. They also have a mesmerising blue glow from head to toe.
Up next were the king and queen of biofluorescent geckos, the reason for this trip – the Namib desert gecko. They have got to be one of the cutest reptiles on the planet, they sit with their natural resting face looking like they have a giant grin stretched across it, huge beady eyes and an oddity of webbed feet that allows them to burrow down into sand.
As we switched from white light to UV their usual sand coloured skin transformed into a deep saturated blue, flecked with black scales here and there. However it is their lower body that holds their masterpiece. Its when viewed from the side or beneath that you can really see their fluorescent colours. Two fat stripes of neon green run from either side of the main body up underneath the jaw and down to the beginning of the tail.
A Strong Case for Biofluorescent Communication
The Namib Desert Gecko is a particularly interesting story in the search for a reptile that uses biofluorescence as a form of communication. As a primarily nocturnal species the natural light source that could excite their biofluorescence would be the moon. The moon is a weak source of light, and only contains a small amount of short wavelengths. For the gecko’s to see each other they would require especially sensitive night vision. Which it just so happens they have.
The Namib Desert Gecko has taken the low-light vision capabilities of cones in their eyes to the extreme. This allows them to see colours in near darkness. In our eyes we have cones and rods. The cones help us see colours, and the rods are what we rely on when it comes to night vision. A number of species of geckos completely lack rods in their eyes, and have instead evolved rather unique cones. Despite spending most of their time in the dark, they’ve evolved oversized cones that are extra sensitive to light.
This provides them the ability to see colour in the night. Their low-light colour vision is 350 times more sensitive than ours. This creates the possibility that they are an example of an animal that can actually see their own biofluorescence excited by moonlight.
The Missing Piece
It was a team of German scientists who discovered biofluorescence in the Namib Sand desert gecko. They published a paper in the scientific journal Nature in 2021 documenting their findings.
They went on to suggest that given their unique eyes, and the brightness of their biofluorescence that these geckos could be using their glow to communicate with each other. They suggested the geckos could be using their biofluorescence to find each other at night. The fluorescent stripes are perfectly placed to be visible to other geckos, but invisible to their predators such as birds, looking down from above.
Even though they have branched off from the evolutionary family tree from the Namib Desert Gecko 70 million years ago, and are located on another continent, two other species have been discovered with very similar green biofluorescent stripes on a blue body. The Arabian Wed-footed Sand Gecko and the Dune Sand Gecko both occupy similar environments of wide open sand dunes. A sparse landscape perfect for a visual signal to be seen from far away. The first observations of geckos in surrounding areas of cluttered gravel plains and hard packed sand have shown they are either not biofluorescent, or have a very weak biofluorescence, seemingly supporting the idea of biofluorescent communication in the open desert for these little reptiles.
Their unique eyes, their behaviour and the intensity of their fluorescent emissions make this a particularly interesting potential for a a case of nocturnal biofluorescent communication. For now at least, there have been no follow up studies to prove this either way. Big questions still remain, it is unknown how bright their biofluorescence is under natural lighting conditions. And the biggest missing piece is the lack of all important behavioural studies. Without this crucial stage, it is only a hypothesis, rather than a proven case. It would be wonderful to see someone come along and take on the challenge of carrying out behavioural studies to try and find a final answer.
