Wednesday, 23 March 2011

Dance of the Adders

This spring, some of Devon’s snakes will engage in spectacular behaviour known as the ‘dance of the adders’, when two vipers rise up and sway back and forth with entwined bodies. But, this display is not, as it might first appear, a romantic rumba between a courting couple, or, an audition for an animal version of Strictly Come Dancing; in reality, it is something much more violent - a brawl between two guys over a girl.

Adders are unable to function in cold weather and throughout the winter, they have been secreted away, hibernating in rodent burrows and amongst roots, sheltered from harmful frosts. But, as temperatures rise, the snakes begin to stir. Mature males are the first to emerge from their hidey-holes and sometimes appear as early as February. They slither to a sunny spot and bask in the weak spring sunshine to raise their body temperature. If you see them at this time, they may appear a bit shabby, with dull skin and opaque eyes, caused by a layer of oil beneath their scales. They rub themselves against some
thing rough and peel off their old skin, from head to tail. It turns it inside out, like a sock, to reveal a new, brighter, more boldly patterned version. A few weeks later, the females and immature adders rouse themselves from their slumber. And after the female has basked and moulted, the adults’ minds turn to sex.

The female produces a scent from a pair of glands at the base of the tail and wherever she goes, she leaves a trail that males find irresistible, like the ‘Lynx effect’ with role reversal. He follows behind, tasting the air with his forked tongue and drawing scent molecules into the Jacobson’s organ on the roof of his mouth. When he has caught up, he flicks his tongue, in and out, over her body. The pair may quiver their bodies and tails and if the female is receptive, copulation takes place. The male snake’s reproductive organ is a strange thing, divided into two, forked lobes called hemipenes, which are covered in frills and hooks that ensure the couple stay locked together until mating is complete. For hours or days afterwards, the male guards his female, but if another male appears on the scene, things can get heated. The males rear up and wind their bodies around each other, in an attempt to push each other to the ground. This wrestling match between rival males is the famous ‘dance of the adders’. The larger male is likely to win and chases the loser off, before returning to his post, beside the female. Despite his best efforts, fatherhood is not guaranteed, as the female will have multiple partners and may even produce offspring using sperm from previous years.

Once the important business of reproduction is dealt with, the adders are finally free to turn their attention to finding some food, possibly their first meal in six months and all being well, the next generation of adders will be born in August or September, swelling the ranks of one of Devon’s most fascinating creatures.

Over to you
If you want to watch the ‘dance of the adders’, please remember that these beautiful snakes are venomous. Nobody has died from an adder bite since 1975, but it is still wise to treat them with respect. They are shy creatures and will not bite without provocation, but observe from a distanc
e and don’t attempt to pick one up. Adders can be found throughout the county, in a range of different habitats, including heath, forest and scrub. Dartmoor is a refuge for them and a great place to see them. According to local folklore, Wistman’s Wood ‘writhes with adders more venomous than any others on Dartmoor’. I once went blackberrying at Padley Common, Chagford and suddenly found myself surrounded by half a dozen dozing adders, having blundered right into the middle of them and more recently, I came across several adders on a footpath through a forestry plantation close to Tottiford Reservoir, near Christow.

Another local story says that to find adders you need to look for dragonflies, which were supposedly put on the moor to warn of the presence of these venomous snakes, hovering above them to give their location away. A more scientific approach involves checking out habitat edges such as clearings amongst dense bracken, grassy woodland rides … any sunny spot close to dense cover that the snake can dive into, should danger threaten.

The best time to look for snakes is early morning, during warm (but not hot) weather. Take a pair of binoculars and scan the ground ahead, looking for movement and listening for rustling. Tread gently, as adders can feel vibrations. Basking adders are well camouflaged, but where there is one, there are likely to be several and they are creatures of habit, so they often return to the same basking spot again and again.