Chameleons are certainly some of the most amazing animals in the world! These highly specialised lizards boast a suite of unique adaptations that never cease to impress. Chameleons are mainly found in Madagascar, across large parts of Africa, southern Europe and extending East to India and Sri Lanka š, so sorry no chance to encounter those within Hong Kong natural landscapes. This diverse family comprises over 200 species with half of them found on Madagascar alone, with their sizes ranging from less than 3 cm (the recently described šš³š°š°š¬š¦š“šŖš¢ šÆš¢šÆš¢āthese are so small they would fit on the tip of your finger š) to more than 65 cm (šš¶š³š¤šŖš§š¦š³ š°š¶š“šµš¢šš¦šµšŖ)!
One of the most striking aspects of chameleons is their ability to change their skin colour rapidly. They do this by actively altering the distances between really tiny nanocrystals of a molecule called guanine within specialised cells (known as iridophores) in their skin. Varying the spacing between nanocrystals leads to different wavelengths of light being reflected, resulting in dramatic colour change šØ! Unlike what you might have heard, chameleons donāt change their colour depending on their āmoodā. Instead, like many other animals, colour change is mainly used to hide from predators (by matching their surroundingsācamouflage) or to communicate with potential mates or rivals.
If many lizards live on the ground, the majority of chameleons, however, actually have an arboreal lifestyleāmeaning that they spend almost all of their time in trees š³. Not surprising then that the closest living relatives of chameleons are iguanas, a group of reptiles known for living in trees as well (at least for many of them). As you can imagine, with such a lifestyle, better be a good tree climber. Fortunately, here they excel! Both hands and feet of chameleons are able to grasp tree branches tightly, and their tails are also prehensileāacting like a āfifth limbā, curling around their perches to provide additional support. Interestingly, we see similar adaptations in other animals living in trees, such as monkeys and possums š, all cases of convergent evolution to be adapted to the same environmental conditions.
Chameleons spend most of the day moving quite slowly in trees, but donāt be fooled! They are constantly on the lookout for delicious snacksāand insects in particular š¦. Their large and powerful eyes, which can rotate and focus independently of each other, give them a field of view close to 360Ā° šļø. But while other animals rely on the strength and speed of their body to catch prey, chameleons employ a very special tool: their tongue. They sneak up on unsuspecting insects, and, faster than the blink of an eye, shoot their tongue towards the prey, using a mechanism similar to how we fire arrows from a longbow. Powerful accelerator muscles contract gradually to store energy in elastic collagen fibres surrounding the tongue, until a certain point is reached when this elastic energy is released to propel the tongue forward (at accelerations that can go up to 400 m s-2). Before the insect can figure out what happened, it has already been caught by the sticky tongueāwhich can be up to twice as long as the chameleon itself š ! Imagine this for yourself! The use of elastic elements also means tongue projection is very powerful even at low body temperatures.
As you can see, chameleons are really unique and fascinating animals. While they do not occur in Hong Kong ā rest assured that you can enjoy a close look at our specimen and many other wonderful species at the Hong Kong Biodiversity Museum! Weāll keep our chameleon eyes on you for your next visit.
Text: Jasper Lee
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