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Adder  Facts

What are the signs of spring?

The adder might not be among the most popular animals, but what could be a more striking sign of spring than the male adder, cruising in search of a mate?  Freshly moulted, he looks brilliantly black and white in the spring sunshine.  He is surely one of the smartest animals in Britain.  He is not mentioned by name in "Pied Beauty" by Gerard Manley Hopkins, but he is surely in the frame.  Here is an emerging male adder, and in the picture below, a female –

Why watch adders?

Adders are among the easiest animals to watch – if you can find them.  It is very easy to walk past them, in spite of (or because of?) their strong patterns, because they are not always easy to see.  They will often sit tight as people or dogs go by as little as a metre and a half away.  Here are some adders pretending that they are not there, so they make pictures which are not very impressive –

So the picture at the top of this page is not really typical.  The camera may not lie, but it can record the unusual.

You can sometimes walk past adders without disturbing them.  What is more likely to disturb them is to stand and stare from too close.  From down on the ground you are a large dark shape against the sky. If you stay too long, adders will become uneasy and eventually slide away to their holes.  Once you have found a good place for adders, and you have found out how to watch them without disturbing them, you can enjoy seeing some interesting behaviour.  If you are patient, you will see things that you will never forget.  It is probably as easy to see the life cycle of the adder as that of any other wild animal in Britain, apart from the frogs in your pond.

Adders, like all other snakes, are descendents of four-legged animals, though no amount of external observation of adders will reveal any evidence of this.  Even the adder’s name has evolved: in Old English it used to be called a nadder, which evolved into our version in Middle English.

The name of the newt has gone the other way – around the 15th century, an ewt became a newt.  The Latin name of the adder has remained constant, though many others are subject to a sort of reverse evolution as biologists rediscover earlier authors.  This can be rather confusing to gardeners, as well as to biologists.

Dogs and adders

Dogs and adders do not go together.  Don’t take a dog if you are adder-watching. An adder may possibly (but probably won’t) tolerate being sniffed by a dog, but a sudden movement by the dog, for example if it looks up when its person calls, may result in a strike on the nose or face.

Although the defensive bite may use less venom than a hunting bite, the effects are dramatic.  The dog’s head will swell up, perhaps right back to the neck and beyond.  The collar will have to be loosened.  The dog will probably be very ill, and it may be temporarily paralysed or blinded.  It may even die.  A dog which has been bitten by an adder needs urgent treatment by a veterinary person.

    People and adders    

This female adder looks passive, if you don’t know your adders, but it is actually fully prepared to defend itself.  Its head is up in the alert position, and the front of its body forms a series of curves.  Look at the distance from the head to the bend below it in the picture, and then at the length of body between.  The distance over which a snake can strike depends on its shape just before that event, as we can see from the picture.

In the next picture the colours grade from head to tail of the snake, showing the initial acceleration and the deceleration at the end.

The peaceful adder

The adder is never an aggressive animal.  It is generally very nervous, and will choose camouflage or escape whenever possible.  Adder bites on people are not especially common.  An adder will usually not react if a dog or a person goes by.  You really have to annoy them or tread on them or pick them up to risk being bitten.

Adders do not like disturbance, and may leave an area if they are continually harassed.  If you go abroad, remember that other species of snakes may not be as tolerant as the adder.  Some other vipers are much more aggressive than the adder, and carry much more dangerous venom.  So be very wary if you don’t know the species.

Please respect all snakes

Do treat all snakes with respect.  You are invading their home.  You are a terrifying animal, tramping heavily around and looming out of the sky.  Never pick up any snake in the UK.  Even if you are not bitten, you can easily damage the snake by gripping it, if you are not expert in this.

A good way to watch them is to use low-power binoculars.  Then you can watch for a long time from a distance without disturbing them. Make sure that you buy a pair that will focus closely enough.  The binoculars can help in watching an adder by letting you focussing sharply on the snake, while defocussing the surrounding foliage.

People spotting

I’ve spotted a homo sapiens.  In fact, although I am deaf, I felt its galumphing footsteps thudding through the ground long before it arrived, and I saw it before it saw me, as I usually do.

These "people", as they are called,  must possess very feeble sense organs, as they are generally very poor at seeing anything but birds, butterflies and flowers.

And why do they have to balance upright like that, moving by a sort of continual falling forward, instead of gliding gracefully along the ground as we adders do?  No wonder they are continually trampling on, and disturbing, my home patch.  Adders never fall over, and seldom break bones.

People often trudge around the countryside in great gaggles, carrying large maps, and even compasses.  Evidently their navigational skill is as poor as their sight. Some of them, dissatisfied with their normal means of locomotion, charge through my patch on things called "mountain bikes", flattening the cover that we depend on to survive.  Sometimes they have even flattened one of us.  

Other humans, dissatisfied with the appearance of a bit of countryside, decide to tidy it up, clearing scrub in order to facilitate the maintenance of some other habitat.  In improving conditions for some species, they inevitably worsen things for others.  It pays to belong to a popular group of species.  Evidently the number of legs is important.  Two and four legs seem to be acceptable, with six trailing far behind in popularity.  No legs, and eight or more, are completely unacceptable numbers to most people.  Perhaps humans evolved in a region where snakes, spiders and centipedes were dangerous.

The irrationality of some people is shown by their concern about possible events such as asteroid collisions.  Compare the number of people killed by any size of meteorite during the 20th century with the number killed, directly or indirectly, by the actions of people.

How people communicate

Many people receive their information using large data files called "newspapers".  On very rare occasions these newspapers carry headlines like "Man bitten by adder", and they never mention "Man kills adder", though that is much more common.  And they never mention the millions of times a year that we adders manage to avoid people because we are essentially peaceful animals, who only kill to survive.  What would people do if they were threatened with squashing by an animal with hundreds of times their own weight?

Colours and patterns

Although male adders seem to be almost always nearly black and white, perhaps occasionally  with a hint of very pale green, and more rarely cream, the females vary enormously in colour.   They are on average bigger than the males.  Their ground colour can – rarely – be almost black, but far more often it is a medium tone – sandy or brownish.  Some are almost yellow – others almost orange.  The only thing that is almost always present is the pattern on the back. 

Many people know that the adder has a zig-zag marking all along its back, and that it has a V-shaped mark behind its head.  Neither statement is exactly right.  The zig-zag is complicated by the fact that wavelength often varies along the body.  This, coupled with discontinuities in the phase of the pattern, and the differences between the left and right sides, means that no two adders have the same pattern.  The marking behind the head varies too.  Together with the colour variations, these patterns enable different adders to be recognized fairly easily.  So you can find out whether individuals prefer to stay in a favourite spot throughout the season or whether they move about.

Here is an idealised picture based on sine waves, which are well known in maths and physics.  The two sides of the first pattern are in phase throughout.  In the second pattern the wavelengths differ by about 10 percent, which introduces a progressive phase difference.  In the other two patterns, random phase-shifts were introduced, keeping the same wavelength for both sides.  It looks as if the phase shifts tend to come in pairs, but that is purely a consequence of the randomness.

Most adders have a combination of these patterns, with apparently random variations in both wavelength and phase.  Adder patterns are of course not exactly sinusoidal, because they conform roughly to the pattern of the scales.  But if you look at a large snake, such as a python, you may see that the pattern does not always conform to the scales: some scales have more than one colour.

The diagram below shows some lines generated with a pseudo-random number generator.  The bunching is apparent, but has no meaning.  If you were asked to draw some lines at random, would you have made them so unevenly spaced?

The next picture shows birds that are not quite randomly placed, because they preserve a minimum personal space.

Here is a picture of a small piece of sloughed skin from an adder.

From a distance we perceive the pattern as smoother than it is, thanks to the tendency of the eye-brain system to create form and structure that aren’t actually there.  Without this, cartoons, and probably most kinds of pictures, would not work.  That this facility is not the same in all species is shown by the general failure of cats and dogs to recognize photographs and TV pictures in most cases.  

You can see that the pattern does not fit the scales very well.  This means the the mechanism controlling the scales is not perfectly linked to the mechanism that controls the colour – some scales include two colours.

The picture below shows two parts of a female adder, with both in-phase and out-of-phase markings.

The colours of adders vary so much between individuals that it is difficult to show the full range, especially on computer screens, which themselves can vary.  The two charts below try to show the difference between the female range of colour and the male range of colour.  The first picture shows a range of colours from dark brown to almost orange or greenish.  The second picture includes a range of browns and beiges that are also seen in females.  Of course, intermediate colours between these and those of the previous chart may also occur.  Females may occasionally be almost yellow, but will be much darker than any male.  The background colours of males are rarely darker than a very delicate pale lemon yellow.  The charts also do not include the effects of recent sloughing and of lighting conditions.

  Female colours

  More female colours

Male colours

Cold blooded?

Most people know that snakes are cold-blooded, which is not strictly true.  Without external influences they have no power to regulate their body temperature, as mammals do, so they have to use the ambient conditions to achieve the temperature they need in order to function.  

They bask in order to gain heat and raise their temperature.  But if the ambient temperature is high enough, they don’t need to bask, and so they are not often seen. Adders may bask either curled up or in a more open position, depending on the conditions.  Sometimes they will rest on a substrate that has retained some heat, so that they can remain warm after the sun has gone.

Often they will flatten the body, as in this picture, to increase the surface area which is exposed to the sun.  More rarely they will turn the dark underside to the sun.  They can curl up the body to reduce the heat input, and they can also rest with parts of the body in the shade.

The simplified chart at left shows how reptiles respond to different temperatures.  

At temperatures above and below the optimum, reptiles will rest or bask, respectively.  

In more extreme temperatures they will become dormant, in states known as aestivation and hibernation.

If the temperature goes outside the range for the species, the reptile will die.

Mammals have mechanisms for raising and lowering their temperature, which enables them to perform in a wider range of temperatures than reptiles.  The penalty is that these require energy, which must be obtained either from fat reserves or food.

Basking

If you watch adders methodically, you may find that they are quite particular about where they bask.  One thing they really like is a nice soft dry bed of moss.  Places that look to us like the places where adders like to be are often consistently ignored, even when they are only two or three metres from favourite patches that look almost identical.  By observation you discover the conditions that adders prefer, including the effects of temperature, wind, damp or dryness.  Adders can be choosy about coming out, and they are quite individual in this respect.  They are also not equally nervous – they differ, not only between males and females, but also between individuals of the same sex.

Grass snakes and adders

During much of the season, adders can be fairly gregarious, often curling up together to bask in the sun, as the pictures show.  Sometimes three or four adders will coil together in a complicated  knot.  Yet if one decides to leave, it is done without any confusion.  Why do think they bask together?  Think about a semi-detached house.  What are the thermal benefits of proximity?  Could the adders be safer from predation when in small groups?

Adders will even curl up with grass snakes if those are present.  Then you will quickly see the differences between adder and grass snake.  The grass snake has a yellow crescent on each side of the neck, and its head is shaped quite differently from the adders, with a different pattern of scales.

Grass snakes

The grass snake has no black line on its back, but it usually has markings on each side.  The colours of the grass snakes vary quite considerably.  If you are lucky you may see a pale grey one.  The eye pupil of the grass snake is almost circular, while that of the adder is narrow and pointed at each end.  The adder’s eye pupil is not quite vertical, but when the adder lifts its head in alarm then it does appear to become so.  If you see an adder with a cloudy eye, probably bluish, with no pupil, the adder is ready to moult.  The scale over the eye has separated from the eye.  Snakes, unlike lizards, cannot blink, but their eyes are permanently protected by scales, which must affect their sight.  They probably depend on smell and heat much more than lizards do.  Perhaps the unblinking eye of the snake has contributed to its unpopular status in legend and in real life.

On average, the grass snakes are longer than the adders, though the adders are probably wider for a given length, with a shorter tail than the grass snakes’ long tapering one.

Here are pictures of grass snakes –

Click here for more information about Grass Snakes.

Adder heads –      

Adder  Facts

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