Grass in Scotland

Arnold’s 1995 atlas data), local records centres, local Summary Methods authorities, & Groups and individuals. Revised Distribution It is generally believed that wild grass snakes Original grass record data were gathered from as These data were then plotted in ArcGIS 10, and verified After verification, three records can be confirmed ( natrix) do not occur in Scotland. Most many sources as possible, including the National (Figure 1). Verification involved checking grid references, as wild grass snakes – all from Dumfries & Galloway records have been dismissed as escaped pets in the Biodiversity Network (NBN), Scottish Natural Heritage notes, descriptions, habitat, context, local knowledge and and recorded since 2009 (Figure 2). A further six Central Belt or misidentifications elsewhere (SNH), Amphibian & Reptile Conservation Trust (ARC) and provenance/recorder. In some cases recording schemes or remain as possible wild records that cannot be without thorough verification. This project has other charities, Biological Records Centre (including original recorders were contacted for further information. immediately explained as erroneous or escapes, reassessed Scottish grass snake distribution by and range in date from 1960 to 2004 (Figure 2). verifying all records as robustly as possible. This Three of the possible records are from Dumfries & has shown that there are grass snake records that Galloway, and are from less experienced but cannot be easily disregarded, and suggests wild reliable sources, from appropriate habitat and populations may be present. relatively near confirmed records. Two independent records from Aberdeenshire in themselves seem unlikely, but in context become interesting as both are from the same catchment. Verification The final possible record at Loch Lomond is from a Escapees & Releases reliable source, but may relate to an introduced Grass snakes were popular pets during population as 200 grass snakes were released here much of the 20th Century and there is a at an unknown date. These possible records possibility that records from before the warrant further investigation, while surveys of 1980s relate to escaped pets. Most of Dumfries & Galloway will help determine the these records are from unsuitable habitat. extent of this population. These records could not be confirmed as wild grass snakes and so were disregarded. Discussion Grid Reference Errors Grass snakes are present in the wild in Scotland. Data entry errors are always a possibility, This species occurs at higher latitudes in such as incorrect grid references. The Scandinavia, relying on compost heaps and manure most common error lies with the two-letter piles for egg laying sites, and as such may exist as a 100 km square codes. For example, the synanthropic species in the north of their range. As original record notes reveal that the such, there is no inherent reason that grass snakes Langholm population actually refers to a would not occur naturally in Scotland. Post-glacial record from Windemere where ‘NY’ was colonisation of the UK by some followed entered instead of ‘SD’. multiple successional routes, with different races persisting in the north after they have been Misidentification & Races replaced in the south. This possibility should not A number of records were disregarded be dismissed when investigating grass snake race in where the recorder was inexperienced or Scotland. However, it is possible that topography known to be unreliable. Furthermore, there are c.15 races and habitat may prevent the Dumfries & Galloway of grass snake, of which only one is known to be native. It population from expanding north. Further research was not possible to control for race during verification. is required to clarify the range and origins of Scottish grass snakes. Common Names The common name ‘grass snake’ refers to the adder () in Argyll & Bute, and to the slow worm (Anguis Chris Cathrine fragilis) in much of Scotland. Some records clearly indicated e-mail: [email protected] Tel: 07789 77 11 66 these species based on habitat, description, notes and confirmation from recorders, and so were disregarded. Grass snake (Natrix natrix) © John Wilkinson Argyll ‘Grass snake’ or adder (Vipera berus) © Chris Gleed-Owen Highland ‘Grass snake’ or slow worm (Anguis fragilis) © Chris Cathrine Electronic copies of this poster are available on request.

Background: Location of grass snake (Natrix natrix) recorded by Chris Cathrine in Dumfries & Galloway 2010 © Chris Cathrine