Today we celebrate World Lizard Day. Yes, you read correctly – it seems there actually is such a day! Then again, if there’s a World Snake Day, why shouldn’t there be a World Lizard Day?
While there is a huge variety of lizards in the world (more than 5600 species, I believe) we only have a small subset of geckos and skinks down here in New Zealand – some 60 species in total. Well, at least we have some, unlike snakes, which we don’t have at all.
Lizards are a strange bunch. Even though many of them (like the bearded dragon) look really scary, they’re mostly harmless to humans. Except for the Komodo Dragon, of course. Growing to sizes in excess of 3m, they’ve been known to stalk and attack humans – definitely a thought that could give me some sleepless nights.
The more I learn about lizards, the more surreal I find them. And it’s not just their prehistoric looks – they are blessed with some decidedly odd skills too.
Some lizards, like the chameleon, can change colour. While it is to some extent done for camouflage, the main purpose of this is actually to signal its physiological condition and intentions to other lizards – they can for example show brighter, more aggressive colours when angered, while displaying lighter, multi-coloured patterns when courting. This colour-changing is done using specialised cells called chromatophores, containing pigments in their cytoplasm which can be voluntarily set to different intensities by the chameleon.
Chameleons can also use their tongues to reel in food from a distance of more than two and a half times their body length, by shooting their tongues out of their mouths at high speed. They can do this because their tongues are equipped with powerful, super-contracting muscles that are unique among back-boned animals. The tip of the tongue is covered in thick mucus that sticks to the prey and allows the chameleon to pull its food straight into it’s mouth. Quite useful for a quick take-away snack!
Equally strange, when you think about it, is the fact that many lizards can voluntarily sever their tails when facing danger – an act known as autotomy (from the Greek auto = “self-” and tomy = “severing”) or self-amputation. Even after it has been severed, the tail continues to wriggle, distracting the lizard’s attacker. Amazingly, the lizard can partially regenerate it’s tail over a period of a few weeks (even though the new tail will contain cartilage rather than bone, and may be a different colour to the rest of it’s body).
Even more surreal – and this really gets me – when threatened, some species of horned lizard can actually squirt blood from their eyes! This action, called autohaemorrhaging, not only confuses predators, but the blood also tastes bad thanks to the chemicals it contains. The squirting is done by restricting the blood flow away from the head, so blood pressure inside the head increases, rupturing tiny blood vessels in the sinuses near the eyelids. This bizzare act can be repeated several times, and the blood can be squirted a distance of more than 4 feet.
Honestly, a prehistoric-looking, blood-squirting, self-amputating, colour changing creature with a tongue twice it’s body length – I wouldn’t be able to make that up even if I wanted to! Surely the stuff of science fiction fantasy, and more than worthy of a special day of celebration.