Adder courtship was one of the star turns of Sir David Attenborough’s Wild Isles, but there’s more to this ritual than you may realise
As featured in Sir David Attenborough‘s Wild Isles on BBC One, adder courtship is quite a thing to behold.
Celebrated and feared in equal measure, there is something both undeniably thrilling and a tiny bit scary about an encounter with our only venomous snake. Shy and retiring by nature, yet rich in folklore, the adder is hardly deserving of a villainous reputation, and due to the usual suspects of habitat loss and agricultural intensification has declined across large swathes of the British countryside.
The adder’s name is believed to originate from a mispronunciation of the Old English word of nædre, meaning serpent. And despite struggling in modern Britain, the snake’s tolerance of low temperatures has nevertheless seen it able to colonise woodland edges, heathlands and moorlands right across temperate Europe and Asia, even including a foothold within the Arctic Circle.
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When encountered for the first time, perhaps the most arresting feature – apart from the bold zig-zag pattern running along their backs – is how short and stocky adders are. With the marginally longer females measuring about 55cm from nose to tail, a mature grass snake could easily reach twice an adder’s length. Adders are also sexually dimorphic, meaning the sexes look different. The males’ light grey to cream background colour contrasts sharply with their black zig-zag, while the brown dorsal pattern of the females does not stand out anywhere near as clearly from their pale or reddish-brown colouration. However, both sexes do possess a distinct copper-coloured eye.
Adult male adders will be the first to emerge from hibernation, any time from mid-March onwards, with one thing on their minds: soaking up as much of the sun’s rays as possible to speed up the development of their sperm. After two to three weeks, they will slough their old skin in April and hit the ground slithering, actively looking for females.
The search is made easier by a scent emitted from glands at the base of the female’s tail, which the male mops up with his forked tongue, before registering it using the Jacobsen’s organ at the back of his mouth. Then it is just a question of him following a concentration gradient to the object of his desires. Upon encountering a prospective mate, he will be keen to quickly initiate courtship, which entails constantly flicking his tongue along her back and sides, while moving alongside her body in a rather jerky fashion.
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He may not have it all his own way, however, and should another male turn up while courtship is in progress, a battle will ensue. The two males entwine their bodies and rise up, and this behaviour should actually be considered more wrestling than dancing, with each suitor attempting to assert his dominance by driving the other to the ground. Interestingly, at no point do the rivals attempt to bite one another, with the bigger, stronger specimen invariably ending up on top after a tussle rarely lasting longer than several minutes. The vanquished male will then be left with little alternative than to flee into the undergrowth, leaving the spoils to the victor.
With a gestation period lasting over half of their entire six-month period spent above ground, it is perhaps of little surprise that the females may well only breed every other year. With mating accomplished, the adders will turn their attention towards their first square meal in many months. They will move off to summer feeding areas, which tend to be wetter and crucially have plenty of prey, such as mice, voles, shrews and lizards.
The key to finding adders is to look on sunny and sheltered banks, often before midday. By walking slowly and quietly, with plenty of stops, this should maximise your chance of observing the adder before it picks up on your presence and heads for cover. And finally, do remember that the majority of bites each year are only suffered by those foolish enough to try to pick them up. So, stand back, enjoy the show, and leave the snake wrangling to… well the snakes themselves!
Black adders
Giving their name to Rowan Atkinson’s famous comedy character Blackadder, black adders can be surprisingly common. Appearing black due to a perfectly natural overproduction of the pigment melanin, they will be able to warm up faster, but on the other hand could be more obvious to predators, such as magpies, crows and buzzards.
Sunny side up
A clever adaptation enables adders to spread out their ribs while basking, which flattens their bodies like pancakes. This exposes the largest possible surface area to both the sun’s rays and the rapidly warming ground beneath.
Inner life
Adders are ovoviviparous, meaning they give birth to live young. In another adaptation to life in a cooler climate, their eggs are incubated internally. Once the eggs rupture, an average of about nine young are born in late summer, but will not catch their first meal until the next year.
Five places to look for adders in the UK
1. Loch Lomond and the Trossachs National Park
Adders are perhaps easiest to locate on the eastern side of the loch, on the south-facing slopes around Conic Hill.
2. Carsegowan Moss
This lowland raised peat bog in Dumfries and Galloway is managed by the Scottish Wildlife Trust. Look out for adders in amongst the heather.
3. Thursley NNR
One of the largest remaining fragments of heathland within the county, this Surrey National Nature Reserve still remains a stronghold for adders, despite damage from the large fire in May 2020.
4. New Forest
South-facing sections of old railway track between Burley and Brockenhurst are good places to look for basking adders.
5. Malvern Hills
A number of discreet adder populations still exist among the acid grass and heathland habitats on the ridge line of these Worcestershire hills.
Main image: Adders in South Downs National Park, UK. © www.ivorchuterart.com/Getty