ARC Trustee Howard Inns reflects on a recent discussion about a reduction in his grass snake encounters and what might affect their abundance.

That was the title of a chatroom discussion at the 2021 virtual Herpetofauna Workers Meeting.  Based on the premise that during my regular reptile monitoring trips, predominantly on heathland looking for sand lizards, nowadays I encounter far fewer grass snakes than I used to.  Whilst my memories from decades ago might be somewhat rose tinted, field notebooks don’t lie and one or two other observers felt similarly.  Peter Gillatt was able to share some interesting transect statistics of encounter rates that didn’t show a dramatic decrease for the relatively recent period that data was available for. Many contributors commented on the fact that grass snakes are still ‘findable’ in gardens and various natural habitats in areas ranging from East Anglia, to Kent and Sussex, South Wales and the Midlands

One of the grass snakes that visited my garden in Farnham, Surrey during lockdown

The lively discussion went on to consider the key variables that could affect grass snake abundance, specifically food source, predation and the availability of egg laying sites.  Both John Baker, from his experience around the amphibian rich pool frog re-introduction sites in Norfolk, and Richard Griffiths, from the marsh frog strongholds in Kent, were of the opinion that if there’s a good food source, grass snakes will show up.  They and other observers reflected on the fact that grass snakes do feel quite nomadic in that they will appear for a while and move on and that’s certainly my experience in my garden where the 2020 lockdown did enable me to keep a closer eye on those that did visit my garden to graze on the abundant smooth newts in the ponds. Richard also commented that in areas of Romney Marsh where marsh frogs are absent but common frogs are present, the generally healthy number of grass snakes moving around the area appears to be putting the common frogs under predatory pressure.

We next considered the topic of the predatory pressures on grass snakes. Several observers expressed some concerns over avian predators. As well as the ongoing impact of game bird releases, the increase over recent decades of buzzard and red kite numbers was concerning and several accounts of snake predation by both of these raptors were shared.  

There was also a lot of discussion about the other key jig-saw puzzle piece - the mysterious issue of ‘Where did the grass snake lay its eggs’.  Garden compost heaps were heavily implicated, but sadly not all.  Several enthusiastic gardeners, including me, report building the ideal compost heap but failing to tempt any snakes to use it.  Piles of dumped cut reeds were reported by Pete West as being used habitually by grass snakes in his patch and Silviu Petrovan also reported them breeding in Romania in piles of rotting vegetation brought by flooding waters near rivers.  Interestingly Silviu reported that on the Hampton reserve in Peterborough where grass snakes are doing well, they appear to lay their eggs in banks made of brick piles and another contributor commented on egg laying beneath concrete slabs.

I must admit I was more encouraged after talking this topic through with such a great party of fellow field herpetologists and whilst my dry heathland meanderings don’t bring me into enough contact with my favourite reptile, it’s great to hear others are still finding grass snakes around the country.

Find out more about Howard Inns and other members of ARC's board of Trustees on our Trustees page

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Banner image: grass snake by Nick Dobbs