Adders on the down

A black and white male adder sunbathes on the upper slope of an old pile of fence posts and the chocolate brown female does the same on the lower slope. On another day, a darker male is on the fence pile tightly coiled as the cloud is over; he tastes the air then slides silently away.

There has been a long term study of adders on the chalk downs above the Darenth Valley and, on a hot cloudless day, one of the surveyors kindly explained a little about the work which has been going on between March and October every year since 2008.

Encounter rates are measured at or under reptile mats which have been distributed across the escarpment and individuals identified from unique markings. Some individuals have been followed on their seasonal travels and over many years. Declines in distribution may be due to the south facing downland becoming drier and hotter with numbers remaining healthy on west-facing slopes. Slow worms which are also monitored are also declining in the same habitat, which is less surprising as these rely heavily on molluscs for prey. Common lizards on the other hand are getting more common everywhere. Is this climate change in action? Probably. Long term studies, such as this one, reveal much that is insightful locally but also feeds into a an understanding of change at a continental scale, and with adders in decline across the UK, this is especially important right now.

The flowers of the chalk are also beginning to turn the green sward into a colourful patchwork including crosswort, trefoils and salad burnet. The early purple orchids are going over and man orchids on the way up. Crab spiders sit and wait for insect prey on tall plants; a successful strategy also used by adders that prey on small mammals, small reptiles and nestling birds. Adders will also actively pursue prey.

In the summer of 1979, I approached a stonechat nest on the Surrey heath where my old friend Frank Blackburn had put up a hide to photograph the comings and goings of the adults. All the nestlings were lying dead and an adder was sitting by the nest devouring one of the brood; the other half-feathered corpses each had a neat double puncture mark in the breast. Presumably he or she was going to swallow the lot.

The downland is covered in dingy skippers which seem to be having a good year; grizzled skippers are here too but much less abundant. Small heaths are just on the wing and pairs chase each other low over the slopes for long periods in frenetic dog fights. On the scrubby edges, where the hawthorn is in flower and dog roses are coming out, green hairstreaks sit on prominent branches and chase off all comers with a rapid dash but often returning close by; the undersides have the most brilliant emerald green colour; the upper wings are hardly ever revealed.

4 Comments Add yours

  1. It’s valuable to have data recorded over a number of years…. we’re finding that species disappear before the decline is even noted.

    1. Steve Parr says:

      That is the challenge of monitoring but still a very worthwhile thing to do; it is often rewarding for totally non-obvious and unexpected reasons.

      1. Also for keeping track of the health of species and biodiversity or declining numbers, biodiversity loss. Citizen science projects can also add value 😊

      2. Steve Parr says:

        They are great value – a real win-win for the observers and the organisers/number crunchers…

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