What You Might Not Know About Snakes
“The serpent was more subtle than any of the beasts of the earth” – at least that’s the Bible’s take on this remarkable group of reptiles. Be that as it may, they are certainly one of the most supple of animals and there are plenty of other things about snakes that certainly make them stand out from the crowd.
Whether you’ve been keeping snakes for years, or you’re a real beginner, there’s always something new to learn – and snakes are nothing if not full of surprises.
More Than Meets The EyeOf course, the most obvious thing about snakes is the fact that they have no legs, but that alone doesn’t make them unique. Many animals have adopted a legless body – often to help with a burrowing lifestyle – including a number of their lizard relatives, such as the slow worm, the Scheltopusik and many kinds of skinks, as well as the likes of the earthworm.
Behind the unblinking stare of your pet, however, lies something entirely unusual, since the eye of the snake has a whole range of features that are quite unlike anything found elsewhere in nature.
As anyone who has seen a shed snake skin knows, each eye is covered with a single transparent window scale, but it’s not just the fact that they don’t have eyelids like other reptiles that makes them so different. Internally, the lens is round and yellow – the coloured fluid inside helping to absorb UV light and so protect the eye – and instead of being focused by changing its shape, as lizards do for instance, it is adjusted by moving it forward and backward, a bit like a telescope.
The net result of this makes snakes rather short-sighted on the whole, though how well they see does vary a lot between species, and although they have colour vision, few if any kinds can detect the range of colours that humans do. However, as every snake keeper knows, they’re pretty good at spotting movement.
Anatomical OddityIt’s not just their eyes that single snakes out – almost all of their anatomy has its own surprises.
Their hearts can move aside within their bodies to allow large items of prey to slide along their guts without damage, the usual paired organs – kidneys, ovaries or testes – are typically located one behind the other and in most species, only one lung is actually functional.
Perhaps their most amazing anatomical adaptation, however, is their jaw. Although it is often said that a snake dislocates its jaws to feed, this isn’t strictly true – the reality being far more complex. The lower jaw is extremely supple, the two halves are only held together by a flexible ligament, which allows the bottom of a snake’s mouth to stretch considerably to right and left. Add to this a series of joints in the skull itself and the animal is perfectly capable of engulfing prey whole – even when it is something that is considerably larger than the snake’s own girth.
An Uncertain PastTheir long and fairly fragile skeletons, containing 200 – 400 individual vertebrae or more, means that complete and undamaged snake fossils are hard to come by – although there are some recognisable specimens dating back to around 150 million years ago. This makes it difficult to be entirely sure exactly how they evolved, but there are two ideas which have put forward that might explain their origins.
According to one theory, snakes came from lizard-like ancestors that adopted a burrowing way of life and gradually their legs reduced in size, eventually disappearing to leave them with the elongated, worm-like body we know today and their sight degenerated. Sometime during the Cretaceous period, these early snakes re-emerged above ground – having lost their legs forever, but able to re-develop adequate vision from the vestiges that remained of their original eyes.
Alternatively, the other explanation casts relatives of the Mosasaurs – huge extinct marine reptiles – as the ancestors of snakes and suggests that changes to their bodies came about in response to taking to the water for a period, before later re-colonising the land.
While we may never know where snakes really came from, one thing’s for sure – subtle or not – they really are a very different kind of beast!