Meet John Hartshorn, co-founder of Yorkshire Rewilding Network!

John is a Fellow of the Royal Geographical Society and a Chartered Geographer. His original academic studies were in physical geography and particularly biogeography, with postgraduate specialisation in geographic information systems and science which has, so far at least, given him gainful employment for over 30 years. He has also recently completed a Postgraduate Certificate in “Green Economy”, specialising in biodiversity and ecosystem services, earth system and sustainability science, and environmental law and social justice. With a rural upbringing, his love of nature has led him to undertake a range of conservation volunteering activities including biodiversity surveys for his local AONB and the co-founding of the Yorkshire Rewilding Network of which he is a trustee and committee member. For the last few years, he has been involved in surveying adders annually at a site in Nidderdale for Nidderdale National Landscape. John can be contacted by email: john.hg3@btinternet.com. John’s LinkedIn profile is: https://www.linkedin.com/in/johnhartshorn/

John’s chosen species is the Adder, Vipera berus. A small (60-80cm long) and slightly dumpy member of the viper family of snakes, the Viperidae, the common or European Adder is one of only three species of snake to have reached the island of Great Britain after the last ice advance and before we were separated from the European mainland around 6,000 BCE. Whilst we cannot speak for our other two snakes, the Grass Snake and the far rarer Smooth Snake, which is geographically restricted to a few sites in southern England, it’s no great surprise that the Adder found a home it liked in Britain, as it is no stranger to harsher northern climates, being the most northerly snake species on the planet and found right up into the low Arctic. Indeed, one of its many names is the northern viper, although John also particularly likes the Polish name for it, the “zigzag viper”. You can find out more about the Adder on the NBN Atlas: https://species.nbnatlas.org/species/NBNSYS0000005075.

An Adder showing its excellent camouflage!

But why do we call it the “adder”? Well, this is believed to derive from the Anglo-Saxon word ‘nædre; which was used to refer to any kind of snake. That said, the word for a snake in the unrelated languages of Scots Gaelic and Welsh are suspiciously similar, being ‘nathair’ and ‘neidr’ respectively.

As well as being the most northerly snake species, it’s also one of the most widespread, being found across large swathes of Europe and even in East Asia. Much of this can be attributed to the wide range of habitats that suit it. Whilst in Yorkshire we now most often associate it with moors, lowland heathland, and dunes, it can be equally at home along woodland margins and in clearings and glades, rough grassland and pasture, chalk downlands, and along the margins of water bodies, and even in wetlands if there are enough connected dry patches.

In fact, it’s this mixture and complexity of habitats that particularly suit the Adder but, alas, connectivity between such habitats continues to be eroded through land use change and human disturbance, leading to Adder populations that are increasingly fragmented and isolated. In fact, there have been some concerns raised that many smaller populations of Adder are now becoming inbred which will, eventually, result in genetic bottlenecks and vulnerabilities through a lack of genetic variability, although a study by Ball et al (2020) found that “the most immediate threat to small adder populations is demographic rather than genetic”, but for “larger populations high levels of relatedness indicate that genetic factors are likely to represent a real threat, albeit less imminent, but also less visible and thus more insidious”. You can actually contribute to ongoing research into the genetics of our Adder population by sending shed skins to Amphibian and Reptile Conservation’s Reptile Genebank research project.

Many a wildlife guidebook and, John can vouch, surveyor trainer will tell you that the Adder is one of the few snake species to show sexual dimorphism, which is to say that males and females look different. Males tend to be silvery in colour with black zigzag markings (now does the Polish name for adders make sense?!) whilst females tend to have a browner colouration with chocolate-coloured markings. That’s the theory, anyway. There is significant colour variation in both sexes, including populations that exhibit melanism and contain some individuals that are, in fact, black adders. John has come across many examples of Adders on his survey patch and elsewhere where it has been impossible to decide whether he was looking at a darker male or a lighter female, especially since there is appears to be a tendency towards more olive colouring in the population at his survey site in Nidderdale. If you can see the animal’s tail, you might be able to identify a female by the more distinct narrowing of the main body into the tail, although sometime photos do not always result in a definitive answer! It’s worth noting that Adders can look darker and duller as they approach their first skin shed of the season, known as sloughing. As this gets closer, the skin over the eyes tends to look somewhat translucent and milky.

An darker-coloured Adder, showing their range in colouration.

Being a northern species, the Adder is colder-climate adapted and hibernates in underground hollows and tree trunks known as hibernacula between October and late February, when warmer sunny days will entice males out for some early basking. They can even be seen basking if there is snow on the ground, although they typically seek out patches where the melting has exposed much darker ground than the snow itself.

From March onwards, Adders of both sexes spend a lot of time basking near to their hibernation sites, seeking out small patches that warm up quickly, enjoy significant direct sunlight, and yet have cover into which they can flee if disturbed. They are often very difficult to spot as they are well camouflaged and blend in well to a range of the previous season’s dead vegetation. In fact, the zigzag markings can make an Adder near invisible in last year’s dead bracken.

You might notice that adders flatten their bodies to increase the surface area that’s exposed to the sun, especially if the sun is making only vague attempts to shine through morning spring mist. If several individuals have been hibernating together, you will often find them basking together, even intertwined. However, you might also see males more actively intertwined as they wrestle each other and try to exhaust their opponents in what is known as ‘the dance of the adders’ as they compete to mate with a female close-by. By mid to late April, Adders tend to disperse into the wider habitat and become more solitary as they hunt for prey such as small mammals, other reptiles, amphibians, and even ground nesting birds and their eggs. Many of the females will be pregnant by now, although they typically breed only every 2 years. They give birth to 3-20 live young in August, the young snakes having hatched within the female’s body, which is known as being “ovoviviparous”. The young snakes are typically the size and dimensions of pencils and, given the seasonal vegetation is at its maximum in late summer, are nigh-on impossible to spot until early the following spring before the year’s growing season gets underway.

We have widely distributed Adder populations across Yorkshire, some even right on the edge of cities such as the population at Strensall Common near York. It’s worth mentioning that where you have Adders you invariably also find the Common Lizard Zootoca vivipara, and Slow Worm Anguis fragilis. But, as alluded to earlier, our Adder populations are now generally quite isolated due to ongoing habitat loss and fragmentation. Despite being a priority species in the UK Biodiversity Action Plan and highly protected from any form of disturbance or persecution under the Wildlife and Countryside Act 1981, Adders continue to suffer from increasing human disturbance and, sadly, still some persecution, often fuelled by sensationalist newspaper headlines. Yes, the Adder is venomous. No, you wouldn’t want to be bitten. Yes, keep your dog on a lead where there are known to be Adders. Bites are rare and usually only happen when dogs run free or people accidentally step on a basking Adder or, inadvisably and unnecessarily, pick one up. The truth is that our northern viper is not an aggressive species at all and will flee into cover the moment it becomes aware of you.

Adders are beautiful animals, and we are lucky to have sites in Yorkshire in which they appear to be doing reasonably well. However, Adders should be in many more habitats and locations than they are and should be far more abundant. We must do all we can to reconnect their fragmented habitats and let their populations expand once again.

Monitoring

If you spot an adder, you can record your sighting via The Record Pool, which is an online recording tool set up jointly by Amphibian and Reptile Conservation (ARC) and Amphibian and Reptile Groups of the UK (ARG UK): https://www.recordpool.org.uk/index.php.

If you’re specifically out and about in Nidderdale and spot an adder, you can also contribute your sighting to the Nidderdale National Landscape’s Adder Watch: https://nidderdaleaonb.org.uk/about-us/projects/wildlife-projects/adder-watch/.

Further information and acknowledgements

NEYEDC would like to thank John for his time and expertise in helping to create this blog.

John recommends the book ‘The Secret Life of the Adder: The Vanishing Viper’ (2022) by Nicolas Milton (https://uk.bookshop.org/p/books/the-secret-life-of-the-adder-the-vanishing-viper-nicholas-milton/6535468).

The Natural History of Yorkshire in 100 Species

#51 Adder by John Hartshorn

Monitoring

Further information and acknowledgements