| An Adder in my Garden |
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Jean Lawman uncovers the world of the elusive adder. It was noon and the soporific drone of honeybees busy about the nest in the roof had become fainter. There is said to be a lull in their activity at this time of day that is thought to be due to a dip in the nectar level of flowers. What was very audible on this hot June day was the whirring and crackling of dragonfly wings clashing in the air over the garden pond. The resident Emperor, a large and charismatic dragonfly enamelled blue and green, was in control, lording over the smaller species, but still allowing them their space. Energised by the midday heat, he was challenging and pursuing individuals of his own species, females for mating and males to chase away.  A nearly black butterfly flits lazily among Catmint flowers glittering mauve-blue in the fierce light, the first Ringlet of summer. I descend the steps to watch the dragonflies’ midday melodrama of chasing, copulating and egg-laying, the sun throwing sparks of light from mica crystals in the granite and highlighting the silver trail of a snail. I stop abruptly. My eyes register an unfamiliar form on the bottom step. Fear and fascination grip me, a strange mingling of sensations, as I focus on a large snake spreading its length over the stone. It is an Adder. The snake remains motionless as I do and my irrational fear dissipates enough to study the creature. Its body is flattened to absorb maximum heat from the sun. Judging its size carefully because Adders tend to look bigger than they really are, I reckon it to be a female and about 70cm long, a good size, since the average length for this sex is about 60cm, a little larger than the males. A casual glance and I surely would have exaggerated its length. Maybe the strong pattern on the back is the reason for this. It seems not to have noticed me. Possibly I trod too softly for it to register the vibrations of my footfall through the ground and, with the sun before me, I cast no shadow despite being above it. Perhaps it has not yet absorbed enough of the suns warmth to induce activity. This is a lucky and unusual encounter in my own garden and I freeze so as not to scare it away. I believe it is female because of the size and the colour. It looks ripe and plump, most probably pregnant, and is a beauty. The colours are rich and glistening in this light; the thick dark chocolate zigzag and small flank patches overlie a paler tawny yellow background; the scales are thinly and darkly depicted. Its head is outer-most on the step, the jaws curving round gracefully and narrowing into the neck; the reddish brown eye glints beyond a thick, dark line skirting the side of its head. A forward pointing ‘V’ is stamped on the crown; ‘V’ for viper, the only venomous snake in Britain. The mark overlies the diamond head of the zigzag. There have been Adders here before that must have been male. They were smaller with variable coloration; usually silver-grey, even powder white. Others were blue-green, embellished with jet-black markings. It is said that the underside of the males are blue, ranging from dark blue to a beautiful turquoise, but you have to catch them and hold them up to see it and, there, my courage fails. Uniform black (melanistic) ones are not uncommon; they are extremely handsome with a superb indigo sheen. Some local populations may include a high proportion of these. After some close study, a slow and stealthy retreat to the house was required to fetch my camera. A sudden and clumsy movement would alarm the snake, not through visual cues but because it would sense the vibrations through the ground and would be gone in an instant. I stepped as softly as I could and backed across the lawn. I didn’t see it move, but on my return its rear half had disappeared into a partially collapsed stonewall flanking the steps. Somehow a photograph of half a snake didn’t appeal and, after a many more minutes of observation, it was left in peace never to reappear in that place on that day, or any other despite, regular checking. The Adder may have been using the wall with its network of tunnels and holes as a temporary ‘refugia’ (a summer retreat in times of inactivity as opposed to the winter hibernation quarters). It was ideally situated beside the open, south facing steps that provide excellent basking opportunities. Being close to the pond (adders like wet places in the summer and can swim quite well) with a damp undisturbed field below full of grassy tussocks and divided by earthy hedges, this was an ideal place for them providing there was enough food. Prey like small mammals (shrews, voles and mice) and nestling birds are abundant, and we also have Common Lizards, which are important food items for the young snakes, along with suckling mammals. Adders are widespread and common in Cornwall. The map of distribution for Britain shows the Duchy to be well endowed with dots that represent records, and more particularly in the western parts of Cornwall. There are gaps in the northern and central districts that may represent unsuitable habitat like the heavily grazed parts of Bodmin Moor or could imply a lack of recording effort. The fact that the Adder flourishes though is not surprising considering its potential for colonizing a wide variety of habitats. Many are well represented in Cornwall, for example coastal cliffs, sand dunes, moor, lowland heath, damp grassland, open woodland and scrub and, quite significantly, Cornish hedges. There are four main requisites – holes or chambers for hibernation, summer ‘refugia’, basking sites and summer feeding grounds, and as long as these are well represented they will find a good living. We have seen Adders on our ground for many years; more so after our old potato field reverted to a damp meadow with patches of low scrub and was later reinstated with hedges: not everyone’s cup of tea, but certainly mine. Large piles of granite stone inadvertently left around could serve as refugia, or maybe even hibernation quarters, but more likely the snakes use holes dug by rabbits or foxes for the latter. In many places, old anthills, molehills and cavities within tree roots provide further likely places for summer refugia. Hibernacula, often shared with other reptiles like grass snakes and slow worms, are generally south facing, free draining and frost free with at least some scrub or tree cover close by. Since we see the snakes only in summer they may not hibernate on our ground. Scrub in the field, mostly gorse and bramble, provides good cover for snakes whilst a compost heap and an old tarpaulin slung over a manure heap provide further safe and warm hiding places; the latter when lifted gently is excellent for viewing them. Males often retreat to wooded areas in the summer, and so the ribbon of mature scrub running down the valley, a feature of many Cornish valleys, is useful summer habitat. The only predator of adult snakes in the valley where I live, as far as I am aware, is the Buzzard, a bird that is common and widespread in Cornwall, but as it is rare to see one of these huge birds flying along with a snake in its talons, I believe it is not commonly taken; rabbits are easier to catch and far more common. It is said that corvids (crows, rooks, ravens and jackdaws) and pheasants will take undersized juvenile snakes. More of a threat to Adders, and wildlife in general are, are the summer fires which rage across heath and moor killing all animals that are unable to escape. In Cornwall, we usually start seeing Adders in the early spring (the first are usually reported by late February) although occasionally an Adder may emerge on an exceptionally warm day in winter (they are not sound sleepers and can die from cold if unable to retreat back into the ground). Most emerge when temperatures rise above 9 degrees C. A colleague who always records her first Adder sighting has recorded February 14th as her earliest sighting ever, an unusual St. Valentine’s Day treat! In this initial period of emergence they are seen most often in the late morning and middle part of the day. Calm days of hazy sunshine are the best or even cloudy days if the temperature is right. Males emerge first and seek the sun, staying close to the hibernation quarters where they will moult two or three weeks after emergence. During this early phase basking is of critical importance for both males and females, not just to allow the snakes to be active but for more general metabolic activity like digestion, development of the embryo and maintenance of the immune system. Basking sites usually have a south or southeast aspect for obvious reasons. Our ground faces southwest, but our hedges, grassy tussocks and gently sloping land provides suitable and discrete sites with a microclimate of their own, and they are generally undisturbed. Remember this preference of aspect if you are looking for Adders early in the season when they are at their most sluggish and therefore easier to find. Remember too the words of one naturalist - ‘not only must the seeker go softly but he must have a quick seeing, ever searching eye, and behind the eye a mind intent on the object’. Camouflage is important at this stage. Much rough land in Cornwall is covered in bracken and, although not good habitat for Adders when it is a tall and mature, earlier on in the season the open nature of the ground and the tawny matt of dead fronds serves the Adders well. They blend in perfectly and are able to lie in relative safety absorbing the warmth of the sun, the curvy zigzag imitating the wavy edges of the fronds and the dark and light tones of the coiled body cryptic against the partly shadowed ground. After a winter underground, the males are at first dull and hard to tell from the females, but as soon as they slough their skin they become bright. Rubbing against hard objects or rough surfaces aids this process. This year, possibly because of the cold and prolonged winter, the males seemed to be later making this change. Mostly they have moulted by early April. It is the trigger for mating, and after the sloughing, they move further away to favoured basking sites and await the females. This is a time of combat as well as mating and thus the spectacular ‘adder dance’ which takes place between two males in the presence of a female (although she may be hidden). It happens when the two males meet and challenge each other, but few people have been lucky enough to witness it. The excited male Adders become very active, cruising at a fast speed through the vegetation, sometimes high up, often ignoring the presence of human observers, some of which have experienced the snakes gliding over their boots or passing between them. The dance takes place when they actually physically meet, and is a ritualistic affair, not designed to injure or kill but simply to assert dominance. The bodies rear up and may entwine, the idea being to try to knock or flick the opponent to the ground. Even if this happens there may be more frenzied chasing before the smaller and weaker snake finally retreats. The winner takes all - his prize is to copulate with the female, who has until then shown little interest. By mid-May mating is usually over and the snakes disperse to their summer feeding grounds that can be up to 2km from the ‘hibernacula’ and cover 5 square km. of ground. Females are less mobile, being heavier and often pregnant; they tend to stay closer seeking more open areas than the males where they bask for long periods to incubate the growing young inside them. The latter retreat to shadier places like hedges, or even woodland, where temperatures are generally higher and basking less critical. Temperatures can be too high for the snakes and anything over 16 degrees C. will cause them seek cover. Low growing vegetation is important then, since it provides good hunting ground as well as physical protection. There is a definite preference for wet ground in the summer – damp pastures, wet heaths, marshes or bogs that tend to be low lying. The cycle is somewhat erratic with the females only breeding every three or four years and sometimes not breeding at all until five or six years old. With the males too, because of the hierarchic structure of the population, only about 30 per cent will mate; they tend to be the larger, stronger ones. Just how they find each other, or rather how the male seeks out and finds the female so effectively, is still a mystery, but chemical cues released by the female and dispersed on the ground and into the air appear to play a part. The rapidity in which they find each other has led some researchers to believe that there are others factors coming into play; an inherent knowledge of the local landscape for example involving a learning process or maybe even geographical imprinting. This is feasible since Adders are site faithful and do not move far from traditional haunts. Also Adders can live for a very long time, certainly over 30 years, so this kind of skill is likely to be of great benefit to them. After mating, the snakes are dispersed over a wider area, the females needing to feed excessively to nourish the developing young inside them. They give birth to the live young at some time during mid-late August close to or within the hibernation quarters. The following spring the cycle begins again. Adders bite as everybody knows, a fact that can’t be ignored, but it requires serious provocation for them to waste precious poison on defending themselves when it is needed to secure the next meal. To get the matter into perspective, more people die from dog attacks, lightning, golf balls and wasp stings. The prey is attacked with a single efficient strike and dies in a few minutes, the snake carefully following its trail. The poison glands lie behind and beneath each eye while the fangs that they supply are folded back in the side of the upper jaw. Sometimes the fangs are embedded in the prey, but they are quickly replaced by a new set waiting to come into operation. For many people, because of the bite, the Adder something to be avoided and despised, even killed, which is a great pity because there is no doubt that it is a fascinating and beautiful animal. We should consider ourselves lucky in Cornwall that we host a large population. In the winter when the pond is dark and still with no insects to ripple or fleck the surface with shadows, I will remember the Adder and the bright, hot days of summer. |