Creature Features: Snake Senses and Physiology

Snake Senses and Physiology

Snake Eyes

No, not when you roll a one on a dice. Actual snake eyes, on actual snakes. We’re talking about snake senses and physiology. Snakes generally have good vision, some of them have slitted pupils like cats. All snakes lack eyelids, instead they have a clear scale covering the eye called the spectacle.

You can tell if a snake is due to shed its skin because the eyes go cloudy. Fluid is secreted under the old skin to lift it off to be shed, and this causes the cloudiness. Snakes are vulnerable during this process so they can be more aggressive than usual if disturbed as they are blind.

Some snakes also have the ability to ‘see’ infrared to find prey in the dark. Pythons, boas and pit vipers have indentations on their upper lips called the ‘labial pits’ which sense infrared. The image shows the little holes along the top lip of the snake, these are the labial pits. Each group of species evolved these things separately, and they are also believed to play a role in temperature regulation as well as hunting. Like night-vision goggles essentially, isn’t that cool?

Snake Tongue and Sense of Smell

Snakes use their tongues to detect scents. So when you see their little forked tongue flicker out, that’s what they’re doing. Most people know this. The tongue collects airborne particles and feeds them to the ‘vomeronasal organ’ also known as the ‘Jacobson’s organ’ inside the mouth. This organ is present in most animals, but not humans and aids in scent detection, especially pheromones. So it’s important for detecting prey, predators and potential mates.

Snake Skin

Snake skin is highly specialised to protect their bodies and provide grip for their unique form of movement. Lacking legs means that snakes must move flat along the ground, so their scales help them grip the surfaces. Many species can make use of this to climb trees as well and even smoother surfaces to an extent.

Snakes are covered in scales – some are smoother, others are ‘keeled’, meaning they have a ridge down the centre. Their dorsal scales, the upper body scales, are usually loosely diamond-shaped and arranged in interlocking rows. Their ventral scales (belly scales) are usually singular and wide until the vent, after which they are paired until the end of the tail.

Ecdysis means shedding of the skin. This is something all snakes go through as they grow. Younger snakes will shed more frequently than older snakes. The process takes a bit of time. The new scales grow underneath, and fluid lifts off the old scales.

This is when the spectacle goes cloudy. The snake will not feed during this process, but usually will feed soon after. Normally the snake sheds its skin in one long piece. They rub their chin on something rough like a rock or tree, and slowly wiggle their way out of the skin.

Rattlesnakes have a unique set of scales on the end of their tails. They build up from previous sheds and form a hardened collection of scales which makes a sound when shaken. They use this as a warning to predators, and it gives them the name.

Reproduction

Snakes reproduce sexually, with internal fertilisation. Most species lay a clutch of eggs, which are left to hatch and fend for themselves. Some species stay with the eggs and care for them until they hatch, like pythons.

A few species are classed as ‘ovoviviparous’, which means they keep the eggs inside until they hatch and are ‘born’. So this is a kind of inbetween egg layers and live birthers, if you will. Rattlesnakes are an example of this.

There are a couple of species that have true live births. The boa constrictor and green anaconda both have placentas as well as yolk sacs for their young and give birth to live snakes. They don’t produce eggs.

A phenonemon called parthenogenesis is seen in a couple of snake species. Parthenogenesis is a form of asexual reproduction, where a female animal can produce fertile eggs without mating. Copperheads and Cottonmouths are capable of this, although they can also do it the old-fashioned way.

Feeding Snakes

Snakes are carnivores and eat animals, occasionally eggs but mostly smaller animals. They eat their prey whole and take a while to digest their meal. Some even eat other snakes in some cases. Snakes can’t bite off or chew their food, and are specialised towards this as discussed last week.

Snakes tend to be ambush predators and will strike quickly to catch their prey. Venomous snakes bite and inject venom to kill their prey before eating it. Other snakes will use constriction – wrapping their bodies around the prey and squeezing it until it dies before they slowly swallow it.

They then go and rest to digest their prey. Ideally they would keep their body temperature around 30 °C (86 °F) and as they are ectothermic they will move to a location to keep their temperature around that level. It takes some time to digest but they can digest everything but hair, feathers and claws. These indigestible parts are excreted within the faeces of the snake. Snakes don’t eat often, depending on the species and size of the previous meal this can range from once a week to a couple of times a year! Younger snakes need to eat more frequently so they have energy for growth. In captivity it’s important not to overfeed snakes. But they can also go a long time without food as well, over a year in some cases.

Thanks for reading!

Thanks for reading this rundown of snake senses and physiology. Next week we’re going to talk about venomous snakes and the dangers snakes can pose to us. If you missed the first part, you can read about snake anatomy here. Don’t forget to subscribe to be updated when a new post is live and find me on my social media channels.

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