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Water Vole

Water Vole © David Gibbon

Most people’s first discovery of a Water Vole Arvicola amphibius is through Kenneth Grahame’s The Wind in the Willows; the character Ratty is in fact a Water Vole. The Water Vole is often known locally as a water rat, and at a casual glance does have some similarities in appearance with a rat, leading to some cases or misidentification and persecution. Although a little smaller than a rat, it is Britain’s largest vole with a typical head and body length of around 190 mm and a weight of around 220 g. In Britain the Water Vole spends much of its time in and around an aquatic environment with its burrows seldom more than two metres from a bankside. Here it feeds on the wide range of vegetation types which form its staple diet and it uses the water to escape most of its natural predators; its characteristic “plop” sound, made as it dives into the water to escape predators, is one of the classic signs of a Water Vole (Harris and Yalden, 2008).

The Water Vole in the UK is known to form two distinct groups (clades) with those in Scotland forming a separate phylogenetic clade from those in England/Wales. Comparison of mitochondrial DNA variation with Water Vole populations across Europe indicates that the Scottish clades derive from an Iberian source, whereas the English/Welsh ones derive from an eastern European source. Initial analysis of the DNA from droppings in museum collections had shown that those from Northumberland, Windermere and Scarborough clustered with the England/Wales samples while one from Berwick clustered with the Scottish samples (Piertney et al, 2005). In 2008 the Environment Agency ran a survey to collect samples of Water Vole droppings from across the North East for DNA analysis to try and refine and update the Piertney study. Droppings were collected from a variety of locations across Northumberland, Durham and Cleveland and including the North York Moors National Park. The droppings from all of the sites across the North East and North Yorkshire proved to belong to the Scottish clade (Fiona Morris, pers. comm., 2011).

Water Voles are historically common across much of the North East with the majority of the pre- 2000 records coming from Tyne and Wear, Durham and the Tees Valley. The Provisional Atlas of the Mammals of the British Isles (Arnold, 1978) documented the distribution of Water Voles in the North East and highlighted the Tees Valley, Tyne and Wear and north Northumberland as areas containing Water Voles. This work involved 35 surveys and produced 30 positive site records.

In 1986 Peter Davis coordinated a Water Vole survey of the North East (Davis, 1986) of 85 sites and recorded positive records in 69 sites. This highlighted an expanded 10 km distribution of Water Voles in the Tees Valley and Tyne and Wear, with a reduced number of records for Northumberland, although the latter was attributed to poor recorder response compared to the 1978 survey as a possible factor. The survey concluded there was no change in status of the Water Vole in the North East at the time.

However by the late 1990s two national surveys (Strachan et al, 2000) had calculated a site loss across the country of 94%, making the Water Vole Britain’s fastest-declining mammal and sparking considerable concern about its conservation. Using the 1978 and 1986 surveys as a baseline this appears to gives a measurable period for the beginning of the Water Vole’s decline. The decline is now considered to be largely due to predation by the introduced American Mink Neovison vison (Harris and Yalden, 2008).

Ironically, after 2000 the number of Water Vole records has increased dramatically as its legal and conservation status was raised, though surveys have nevertheless highlighted its continuing decline. In 2006 the Environment Agency conducted a Water Vole survey in the Northumbria Area and Tees catchment (E3 Ecology and Durkin, 2006). It surveyed 265 sites with previous Water Vole records, including records from local Wildlife Trust surveys and suspected sightings records from members of the public. It also surveyed a further 100 new sites across the Northumbria Area and Tees catchment in areas where surveys for Water Voles had not previously been undertaken. Of the recorded Water Vole sites only 39 were found to have positive signs indicating active Water Vole presence; a further 13 sites were considered to have old signs of Water Vole activity, and 14 more were considered to be suspect for Water Vole presence. Therefore only 14.7% of previously occupied sites still held Water Voles.

Water Vole © Kenny Crooks

The “re-survey” identified a number of key areas for Water Voles: 7.7% of positive sites were situated within the catchment of the River East Allen at Allendale; 12.8% within the catchment of the River East Allen near Allenheads; 7.7% within the catchment of the South Tyne River near Alston; 17.9% in the Tees catchment near Langdon; and 7.7% in the vicinity of Houghton-le-Spring. Of the “new search” survey sites, five were found to have positive signs indicating active Water Vole presence, a further four sites were considered to have old signs of Water Vole activity but no longer to be active, and a further one was considered to be suspect-active for Water Vole presence. The results of this survey are mirrored elsewhere on a finer scale. In Hartlepool, where Water Voles have perhaps been surveyed more than in any other borough in the region over the past 15 years, the number of sites has gradually decreased. In 2002, 10 sites where Water Voles were known to have been previously recorded were surveyed, with Water Voles signs being found at all sites (Parker, 2002). A re-survey of the same sites in 2006 found signs at seven of those 10 sites (Glister, 2006) and by 2009 this had decreased to five of the same sites (Slaughter, 2009).

This decline appears to be continuing with only two subsequent records to 2012, both of which appear to have been transient individuals (Ian Bond, pers. Comm., 2012). The situation appears to be similar in much of the Tees Valley. In the borough of Darlington, where the species was widespread in the late 1990s, there have been no confirmed records for several years (Ian Bond, pers. comm., 2012). In Stockton there is a positive record for the Hartburn Beck from 2012 and three records from the Lustrum Beck from 2010, whilst in East Cleveland Water Voles are only thought to exist now on the Chapel Beck in Guisborough: but the species’ continuing existence on all of these watercourses is probably tenuous (Kenny Crooks, pers. comm., 2012). The populations on the urban becks in Middlesbrough appear to remain healthy though these are small, isolated habitats. It may be that the only place remaining in the Tees Valley where a population is likely to be viable in the long term is on the North Tees Marshes around Saltholme and Cowpen Marsh, extending as far as Cowpen Bewley Woodland Park, where there are many interconnecting ditches, reedbeds and other water bodies.

Our distribution map shows a cluster of post-2000 records in East Durham though these were largely small, isolated colonies. There is very little current information on the status of these colonies but it is anticipated that many of them will have subsequently disappeared. A Water Vole survey in 2001 in the City of Sunderland found 17 positive Water Voles sites from a total of 83 surveyed and a subsequent survey in 2007/08 revisited and expanded on this survey and highlighted Rainton Burn and the River Don as containing good Water Vole populations. Together with records from South Tyneside this highlighted the River Don as a continuing stronghold for Water Voles.

Unfortunately this situation is not repeated north of the Tyne. A Water Vole survey of the Borough of North Tyneside in 2002 (O’Hara, 2005) found that Water Voles were present at 13 of the 53 sites surveyed (25%), and as a result of this a large amount of practical improvement work was carried out to safeguard the population’s survival. However it appears that all colonies have now been lost from the urban areas of North Tyneside and Newcastle in the past 10 years including well-known sites such as Gosforth Park and the Ouseburn, with the last remnants disappearing from the streams and ditches around the Rising Sun country park in Wallsend in the last five years (Kevin O’Hara, pers. comm., 2012). The continued presence of Mink appears to have been the main factor, but in urban areas the urban sprawl and associated high rat presence has had a major impact on fragile and isolated colonies.

Water vole

The situation is little better in much of the rest of Northumberland where it was once widespread and was even recorded from Lindisfarne (Perry, 1946). Populations in the north of the county, including in and around Wooler, have also disappeared although there are still unconfirmed reports of their presence further up on Wooler Common, and new populations were found at Berwick Moor, east of Chillingham, in 2009 which are still present, if elusive (Kevin O’Hara, pers. comm., 2012).

As lowland Water Voles have declined in number, upland areas have been found to contain significant populations. In 2006, Northumbria Mammal Group worked with the Northumberland Wildlife Trust on the “Researching Ratty” project, which aimed to locate populations of Water Vole in upland areas of Northumberland, where it was considered very rare but still surviving in some of the more remote areas. The project focused on three main areas: Otterburn in the southern Cheviot range; Allendale and the upper south Tyne in the North Pennines Area of Outstanding Natural Beauty (AONB); and areas around Haltwhistle in the west of the county. It implemented 72 Water Vole surveys at those locations, identifying 26 sites displaying positive signs of Water Vole presence.

Further survey work by the Environment Agency and the North Pennines AONB Partnership has identified strong and connected colonies in the upper reaches and tributaries of the rivers Tees, Wear, South Tyne and East Allen. Other areas which contain Water Vole colonies, but which do not appear to be quite so densely populated, include Lunedale and Baldersdale, the Cumbrian fellside around Melmerby, the very highest tributaries of the rivers Derwent and Devil’s Water, the top of the West Allen and lower tributaries of the South Tyne, which were only discovered in 2011 (Andy Lees, pers. comm., 2012). These surveys were not able to detect a growth or decline in either numbers or range. However the latest and most comprehensive surveys by the North Pennines AONB Partnership between 2008 and 2011 failed to find evidence of Water Voles in the Plenmeller and Halton-lea-Gate areas of the South Tyne valley where they had been recorded between 2004 and 2006.

The continued presence of Water Voles in the upper reaches of North Pennines rivers and streams is probably a reflection of the well-connected habitat and the low number of terrestrial predators in some areas. Anecdotal evidence from some gamekeepers suggests that mink made a sudden appearance around 1999, particularly in the Tyne catchment, and that this may have led to the demise of Water Vole populations downstream of the current populations. Certainly there are anecdotal accounts of Water Voles in these areas from as recently as the 1990s. Very few mink are reported now and intensive gamekeeping in and around grouse moors keeps down the numbers of common predators such as Stoats Mustela erminea as well as any invading mink. Recent research (Webb, 2011) discovered that the two factors which best predict the presence of Water Voles on individual watercourses in the North Pennines are the width of the water course and its rate of flow. Water Voles tolerate a range of flow rates in narrow streams, but only slower flows in wider watercourses. This is borne out by experience which shows that Water Voles in the North Pennines are found predominantly on narrow watercourses and can be found at high altitude and on steep slopes (over 45 degrees). They are less frequently encountered on main rivers, but where they are this tends to be in areas where colonies are dense and/or where flows are slower. The smaller mining reservoirs (for example those above Allenheads) are also often good places to find Water Voles.

The existence of Water Voles away from water courses is an intriguing possibility in the North Pennines. There are a number of records of Water Voles caught in mole traps hundreds of metres from the nearest water course and they are frequently found using underground stone drains or “cundys”. Droppings can sometimes be found in wet rushy vegetation some distance from streams. Whether or not Water Voles are frequently living away from open water is an unanswered question, but the current survey technique of following watercourses to look for signs will certainly be skewing the results. In order to try to combat the continued loss of Water Voles across the North East a Regional Water Vole Steering Group has been set up, currently chaired by the Environment Agency, to investigate ways to conserve this species. This includes the possibility of captive breeding and/or translocation. Concerted efforts such as re-introductions and, crucially, mink control, may hold out some hope of maintaining the species in its few remaining outposts or perhaps even of limited expansion. Almost everywhere else in the region, and certainly in the lowlands, it appears to be currently teetering on the brink of extinction.

Written by Jonathan Pounder (last updated Nov 12)