The Barred Grass Snake (Natrix helvetica)

What a beautiful snake! Natrix helvetica, the barred grass snake. Once a sub-species of the European grass snake (Natrix natrix helvetica) genetic analysis led to its reclassification as a separate species in 2017. This one is photographed in France. (Credit: J-Luc by GFDL)

One of the interesting things about the natural world is our knowledge of it is ever changing. It shouldn’t be a surprise, nature itself is always changing. Growth and change are fundamentals of biology – they are the very nature of evolution.

Yet we, bless our little confused, inside-the-box brains, are always trying to fix things down. We like discrete, we like organised, we like labelled and defined.

This serves a purpose, of course. If someone in Bosnia is studying grass snakes we need to know and understand the differences between the population of grass snakes in Bosnia and those populations in the UK. How are they similar? How are they different? What does this mean for protecting or managing those species in those areas? What prey do they prefer? Is it different depending on their environment? How will those differences affect the species moving forward?

Making sure we are discussing the same thing is vital for science and that requires classification.

Not even my rubbish phone camera had me feeling blue about seeing this grass snake. What do you mean you can’t see it!? If you see the slight disturbance in the water just left of centre, that’s a grass snake swimming in the canal! I had seen a grass snake once before, but had never seen one swimming so I was so happy to see this! (Credit: Me)

But the goalposts are always moving.

Evolution by means of natural selection is a slow process, thankfully! We do not have to chase around the world’s habitats tracking a glut of speciating shape-shifters. Though there are species that can demonstrate evolution in action by their phenotypes (the observable expression of genes – things like size, colour, or even behaviour.)

The textbook example is the peppered moth (Biston betularia). A simple explanation is this; Peppered moths can exist in two shades, light or dark. Light moths used to be the dominant group because these moths would rest on trees with light coloured lichens on them and were thus disguised from predators. Dark moths would stand out and get eaten.

A pair of peppered moths exhibiting their two colour morphs – the light (above) and the dark (below). This species is commonly used as an example of evolution. (Credit: Siga CC-BY-SA-4.0)

However the industrial revolution produced a huge amount of environmental pollutants, such as sulphur dioxide. This killed the lichen that the light moths were using for camouflage. The result? After 1819 the numbers of dark peppered moths increased dramatically. They were now the well camouflaged population and the light coloured moths were getting gobbled up by the predators.

Naturally this example, this model, is not without its controversies and We Lack Discipline’s ‘First Rule of Everything’ applies – It’s always more complicated than that!

However it gives an excellent example for explaining the mechanisms of evolution, and cementing in the minds of people just how changeable our world is.

“What the fuck’s this got to do with snakes?” I hear you ask!

Well when I first entered the world of biology the UK’s grass snake was considered a sub-species, Natrix natrix helvetica, of the European grass snake, Natrix natrix.

A grass snake (Natrix natrix) eating a newt! Not sure the newt looks too happy but that snake is definitely pleased! (Credit: Böhringer Friedrich CC-BY-SA-2.5)

But as of 2017 there are now no native individuals of the species Natrix natrix in the UK.

Thankfully not because we drove them to extinction! But because, like with organisms in nature, human knowledge grows and changes – it evolves.

In this case it is the use of genetic data that led to the discovery that the UK population (and populations elsewhere, e.g. Italy and France) were sufficiently different across certain genetic markers to be considered their own species. We no longer have any native European grass snakes (Natrix natrix) in the UK because we discovered they are different enough to be their own species, the barred grass snake (Natrix helvetica).

There may still be Natrix natrix living in the UK but they are uncommon and believed to have been introduced from the continent.

So maybe you’re thinking ‘what the difference? A snake’s a snake’s a snake!’ But you’d be very wrong. Superficially they are very similar. They have a browny-green upper body, pale belly, distinctive yellow/white collar, a bit of patterning (which can be used to tell individuals apart). They are members of the family Colubridae, the largest snake family. They are oviparous – that means unlike every other reptile in the UK they actually lay eggs, often incubating them in decaying leaf litter or in compost heaps to keep them warm in our changeable, chilly climate.

This snake has also been reclassified. Once another sub-species, Natrix natrix astreptophora, the Iberian grass snake, is now considered a separate species, too. Say hello to Natrix astreptophora! Photographed in Spain. A cute little juvenile, no less! (Credit: Bernard DUPONT CC-BY-SA-2.0)

Behaviourally they are both shy, mostly harmless to humans as they will slither away rapidly if disturbed. They are semi-aquatic and love spending time around water to the extent they are also known as the ‘water snake’, swimming regularly and using the waterways to hunt their preferred amphibian prey. Though they are also known to eat fish, worms, small rodents and birds should the opportunity arise. Unlike our friend the adder our grass snakes are non-venomous so they rely on stealth and strike to take their prey unawares and will usually swallow it whole.

Their defensive behaviours are fantastic! For one thing their anal glands can be used to produce a pungent odour (insert jokes about your friends or family members being grass snakes here).

But they also fake death, a phenomenon known as ‘thanatosis’! It’s not an uncommon behaviour in nature, or in snakes, but it is something to behold. This theatrical thanatosis will see them coil up, mouth agape – sometimes gasping a few final ‘death rattle’ breaths – sticking out their tongue and hoping that whatever is putting them in danger buggers off and leaves them alone (because what’s the fun in eating an already dead snake when you don’t know what it died from) at which point – and to me this is the second best bit – they will make a stunningly miraculous recovery from their death to get the hell out of there as fast as possible!

A short clip of a grass snake faking death – a phenomenon known as thanatosis. (Credit: Nature Picture Library)

So what’s the first best bit of this behaviour? Autohaemorrhaging! A big word that means making itself bleed! In the case of the grass snake this is nature’s version of ‘blading’ in pro-wrestling. If you’re unsure if your display of death is grisly enough to deter the danger you can always just make yourself bleed from your nose and mouth to add a bit more drama and realism! I’d love to see it – though hopefully not with me as the danger the snake is bleeding for.

So yes, the two species are incredibly similar in both appearance and behaviour. But genetically they are not and this is important. Because that means both Natrix natrix and Natrix helvetica have scope to change in different ways. It could even be that the UK’s population, separated from their mainland counterparts, could evolve into a whole new species again over time. It could be that changes in the environment in Western Europe lead to helvetica making changes to its behaviour or diet that natrix doesn’t. Now we know and understand the differences we can keep an eye and see how that presents itself moving forward.

And why would we not want to study more? To know more about these beautiful and very peaceful creatures? I’m a predator nut, I love predators and decadently bask in the glory of the hunt, the chase, the stealth, the death. I’m grim like that. But the grass snake I love for its seeming pacifism. Yes, the hunt and they kill. But their defensive behaviours are far more charming and fascinating than their offensive ones.

Something about the peace and placidity of a grass snake swimming – it’s zen-like, relaxing. It’s cute. How can you see this juvenile Natrix helvetica and feel fear? These are such gentle, beautiful creatures – unless you’re prey! (Credit:
Syrio CC-BY-SA-4.0)

My enthusiasm for the UK’s snakes has not been met in kind. Many people I have spoken to about it have conveyed how they didn’t know snakes like that existed on these shores, how unnerving it is to think a 1.5m long grass snake could be laying eggs in their compost heap, or how – unlike me, given my smile when I spotted my snakes – they’d never like to see one.

Human relationships with snakes go back a long way. There are ideas, hypotheses (disputed, of course) that a fear of snakes can trace its way back to pre-human ancestral species that were on the menu for snakes. We must fear snakes to survive. The ‘Snake-Detection Hypothesis’ (disputed, of course) suggests that our heavy reliance on sight as a sense, the human visual acuity, may have evolved so that we could spot the dangerous snakes.

But if that were true would our behaviour not have changed as we came to dominate the natural world and made snakes less of a danger? Should we not be a little better at seeing them for how amazing they are?

And human cultural associations with snakes are complicated. I mentioned in my adder article some more positive symbolism regarding snakes – their associations with wisdom, healing and rebirth. That’s not universal though, and certainly post-Christianity the snake evolved into a sly, cunning deceiver.

Adam and Eve and the Serpent – Satan, in the guise of a serpent, approaches Adam and Eve to tempt them to eat of the fruit of the tree of knowledge good and evil and defy God. To what extent has this biblical story influenced our relationship with snakes? From Gustav Doré’s etchings from Milton’s Paradise Lost. (Credit: Public Domain)

“So the LORD God said to the serpent: “Because you have done this, cursed are you above all livestock and every beast of the field! On your belly will you go, and dust you will eat, all the days of your life. And I will put enmity between you and the woman, and between your seed and her seed. He will crush your head, and you will strike his heel.” Genesis 3:14-15

Now unfortunately for God snakes are clearly cleverer than he thought because some of them don’t slither on their bellies but swim the canals, rivers, streams and even seas, they whip themselves across sand-dunes or even glide through the air! They also don’t eat dirt, but a variety of species across various habitats.

But that enmity, that hostility between human and snake is very real. As mentioned in the adder article many instances of adder bites are a person stepping on, or nearly stepping on, the snake and the snake defending itself by biting back. We nearly crush their head, they strike our heel. Is the bible verse based upon past observations of this intimate human-wildlife conflict? What effect has highlighting it, in such a culturally influential text, had on our ideas about snakes?

And where does the shy grass snake fit into that? This gorgeous, harmless species that so gracefully undulates through streams, canals and ponds is not a heel-striker. This is not an enemy. Yet many people fear it.

If this isn’t a beautiful sight I don’t know what is. Grass snakes are semi-aquatic, having amphibians, frogs, toads, newts etc. as a preferred prey in many of their habitats. (Credit: Kentish Plumber CC-BY-NC-ND-2.0)

I wrote an article yesterday about the role of myth and bias in our relationships with animals and it seems apparent to me that aspects of those myths are transferable. After all to many ‘a snake’s a snake’s a snake’!

But in feeling that way, in forming that model of the world and the species within it you ignore the great diversity of lives and behaviours. Two snakes can appear alike and yet be hugely different. Two nearly identical populations can turn out, on closer inspection, to be completely different species.

By clinging to the mythologised view you shut yourself off from fully engaging with the rich depth of relationships and understanding you could have; the understanding of the deep complexities of nature and your role in it. That comfortable simplicity may have been required to survive in the past, but I feel now our survival is heavily dependent on us changing – evolving – those stories to have a greater understanding and respect for the world’s species.

Nature changes. Our methods and understanding of nature changes. In holding a fixed idea, a fixed story, in your head of what a creature is or represents, you do not change. You make youreself static.

But change is vital. It is vital for adapting to new conditions. With habitat loss, human-wildlife conflict, exploitation of natural resources, pollution, the worrying rate of species extinctions, the climate crisis – Our future is heavily dependent on our changing. We are part of this natural world and its peril is our own.

This gorgeous little noodle is not a danger, but a treasure. (Credit: J-Luc by GFDL)

The grass snake is not your enemy. Nor does it want to be. The fact that it would fake its own death if you knocked on its door, and bleed through its mouth and nose to deter you further, would indicate it does not necessarily want to be your friend, either. What the grass snake wants to be is a grass snake.

That may change. Speciation happens and sometimes a N. natrix becomes a N. helvetica. But that’s between nature and the grass snake.

And I’m happy to learn those changes and change with them.

Read about some of the UK’s other fascinating reptiles:

The Common Lizard (Zootoca vivipara)
The Slow Worm (Anguis fragilis)
The Adder (Vipera berus)


Published by Karl Anthony Mercer

Karl Anthony Mercer is a writer, poet, author, musician and part-time dandy. He can often be found squatting in fields looking at insects (he is an unapologetic wasp fanatic), wandering around museums over-dressed, or hiding in a dank corner singing sad songs on a small guitar. His writing on WordPress consists of MercersPoems - an outlet for his poetry often using natural imagery, gothicism and decadence to explore the struggles of living as an autistic person; and We Lack Discipline - Where he writes about factual, often academic topics he has learned and is interested in (e.g. biology, psychology, Roman history etc.) with an inimitable, often light-hearted and irreverant style. You can support Karl by; Subscribing to the We Lack Discipline Patreon - Or buying him a coffee (he loves coffee!) -

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