1. CURRENT STATUS

1.1 Legal Protection

The water vole is listed as a UK and Local Biodiversity Action Plan Priority Species. Protection for the water vole was granted under Schedule 5 of the Wildlife and Countryside Act (1981, as amended) in 1998. It is now illegal to intentionally destroy water voles’ place of shelter and to disturb a water vole while it is occupying such a place. This protection does not prevent maintenance work on riverbanks, but does ensure reasonable care is taken to avoid damage of known sites.

There has been a serious long-term decline in the population in Britain with water voles lost from 89% of their occupied sites this century. Around 70 % of these sites have been lost since 1939. UK surveys from 1989 and 1998 recorded a dramatic rate of decline, with the results for Scotland appearing catastrophic. In Scotland 239/730 sites surveyed in 1989 held water voles, with only 70/730 sites occupied in the repeat 1998 survey.

Research by Aberdeen University and Scottish Natural Heritage (SNH) provides patchy information on local trends in water vole populations and has identified some possible ‘key areas’ for water vole conservation.

Water vole colonies are scattered throughout the lowland farmland of Buchan but they are scarce and declining. In 1990 this area had one of the highest densities of water voles in Scotland. Of 27 sites surveyed by Vincent Wildlife Trust on the Rivers Don and Ythan, 20 contained water voles during a 1990 survey, whereas only 7 did so in 1996, a decline of 65% in only 6 years (Lambin et al 1996). A survey of two watersheds in 1996 indicates that the decline of the water vole has been catastrophic in the watershed of the River Don, with only a few remnant populations, whereas it has been substantially slower in the nearby River Ythan where clusters are still present in several tributaries (Lambin et al 1996). Several populations also persist in narrow burns flowing directly to the sea along the Buchan coastline.

In the catchment of the River Ythan, water vole populations are surviving in small clusters in the headwaters of tributaries. One such cluster located in the Raxton and Keithfield tributaries of the River Ythan has been studied intensively over the last 5 years and holds 200-300 voles in approximately 30 colonies spread over 100 km². The area is surrounded by mink populations, which seem to primarily occupy the main stem and major tributaries of the River Ythan, in preference to the minor tributaries occupied by voles. Detailed studies (Telfer 2000) indicate that such colonies are likely to persist if they are not subjected to further encroachment by mink. Mink are widespread in the Ythan catchment but overall the mink population appears to be fairly stable or declining.

In an attempt to detect other similar clusters of persisting water voles, twelve areas within the Ythan catchment were intensively surveyed in 1998. All areas were centered on known positive sites from the 1996 survey. Several tributaries with good numbers of water voles were found (Telfer 2000).

Extensive surveys in the catchment of the River Dee, Deveron and Don have been carried out by Aberdeen University and SNH. A first survey of the upper River Dee found that water voles were widely distributed in 3 headwater sub-catchments (Geldie-Bynack, Dee, Derry-Lui) where 67 small sub-populations were found in backwaters and slow-flowing sections (Lambin et al. 1998). Water voles have dramatically declined or completely disappeared in sub-catchments of the River Dee (Clunie, Ey, Gairn) which have apparently been colonised by mink during the last 5 years. Further large-scale surveys have taken place in the Grampian Mountains where numerous scattered populations have been located close to the watershed divide. Repeated surveys of Balmoral (Aars et al 2001) and Mar Lodge (Reynolds 2000) have revealed a pronounced decline in water voles in the last two years. This decline partly reflects the natural instability of water vole populations. However, a localised and catastrophic decline took place in the Bynack sub-catchment of the River Dee following mink colonisation in 1999. As a result, the largest population known in upper Deeside was destroyed and to date, has not recovered.

An SNH survey (2000) identified 6 colonies in the catchment of the River Deveron, one colony on a tributary of the Black Water near Cabrach is also known. Water voles appeared to be absent from the headwaters of the River Don.

Water voles are herbivorous, feeding on lush waterside vegetation of grasses, sedges, rushes and reeds. In the winter months roots, bark, rhizomes and bulbs form an important part of their diet. The habitat requirements of river dwelling water voles include a dense cover of lush bank side vegetation, slow-flowing waterways, and riverbanks made of un-compacted soils. Where those conditions are met, water voles tolerate very shallow and narrow watercourses, sometimes heavily polluted by organic matter. Sites excessively shaded by trees are less favoured, and extensive riverbank root systems mean that voles cannot burrow and will not use these areas. In waterside populations each vole uses a series of burrows dug into soft riverbanks.

Lowland habitats range from undisturbed riverbanks with lush vegetation to highly degraded field drains surrounded by intensively farmed field or pastures. In the uplands lochans, small waterways flowing through dense heather with a narrow margin of dense grass and high altitude peaty sites (up to 1300 m) with only limited grass cover are used. Suitable habitats are patchily distributed in lowland area as a result of farming practice. In upland areas, backwaters, wet meadows with pools, small watercourses flowing underground through peat and grass flushes form a mosaic of suitable sites mixed with unsuitable habitat (heather, poor soils etc).

Water voles can be detected by the presence of runways up to 9 cm wide at the edge of densely vegetated banks, by burrows and by latrines containing cylindrical faeces with blunt ends.

Water voles have a high potential for population growth due to their high fecundity and despite their relatively low survival rates. Breeding lasts from April to October and the females may produce two to five litters annually, each of five to eight young.

Individual water vole colonies are typically small, with between 1 and 20 individuals. Discrete colonies are typically between 0.5- 1 km apart but they can be extraordinarily sparse, even in pristine populations, with less than 25 individuals / 25 km². Dense clusters of colonies may include up to 200 indiv / 25 km². Clusters made up of dense individual colonies are less likely to go extinct and more likely to persist as a whole over time. However, even small colonies may be important for survival of water voles if they are part of larger populations.

Individual water vole colonies naturally have a limited persistence, making the protection of single colonies ineffective. It is therefore essential to protect empty sites with suitable habitat to allow recolonisation. Entire clusters persist despite a turnover of local colonies (local extinctions followed by recolonisations). ‘Key areas’ for water vole conservation must be large enough to include a viable number of individual colonies and enough area of suitable habitat. In areas with a dense network of suitable waterways where there are dense clusters of voles, the impact of mink predation appears to be lessened.

The available evidence suggests that the overriding factor causing the decline of the water vole in North East Scotland is predation by American mink. Habitat degradation is an additional secondary factor, aggravating the impact of mink, primarily in lowland areas.

Although they have many predators, water voles are particularly vulnerable to predation by American mink. Water voles and mink do not coexist locally at any site in North East Scotland. Both upland and lowland colonies have been shown to immediately lose water voles after being invaded by mink. Sites permanently occupied by mink or adjacent to sites occupied by this alien predator do not support breeding colonies of voles. Water voles are nearly completely absent from the entire catchment of the River Don where mink are widespread. Water voles have vanished from all known lowland sites in the catchment of the River Dee and only persist in upland areas currently free of mink.

On the River Ythan mink tend to occupy the main stem of the river while water voles are found on small waterways away from the main stem. Colonies have become restricted to the densest part of the waterway network where many suitable sites are available and where colonies are made up of dense clusters. They have completely disappeared from sections of the catchment where waterways are less dense and hence colonies are further apart.

The UK wide eradication of mink is almost certainly impossible on practical, political, economical, and social grounds. Conservation effort must, therefore, focus on a limited number of sites where safeguarding viable populations is feasible.

Lowland water vole populations in North East Scotland are distributed along short sections of feeder streams and ditches in the midst of intensive agricultural land. In these areas, human activities such as dredging or cattle trampling can destroy areas of suitable habitat. Where populations are already on the brink, such activities may be extremely detrimental. Upland colonies do not generally suffer from these pressures.

Heavily grazed sites lack dense grass and may to be heavily poached. Trampling by cattle may lead to the bank being unsuitable for water vole burrows. Grazing by red deer and to a lesser extent sheep in the uplands undoubtedly reduces grass cover, especially where locally base-rich sites favour the growth of grasses. However, such heavily grazed sites are often used by water voles that restrict their activities to underground burrows and runs.

Dredging of key sites with water voles or sites that are suitable for water vole colonies, but are presently empty can be devastating. Dredging of field drains results in habitat destruction. Recovery of the habitat can take a considerable time with badly affected habitat remaining unsuitable for over two years (Telfer 2000). Legal protection under the Wildlife and Countryside Act is only effective where landowners intending to dredge a site are aware of the presence of water voles. Culverting and canalisation effectively cause a complete and permanent loss of habitat. Where long sections of waterways are drained this may represent an important loss of habitat in populations which are already under pressure.

3.5 Fluctuations in water level

There is no evidence that fluctuations in water level are having any detrimental effect on water voles in North East Scotland. Water voles are naturally adapted to living in wet areas and temporarily relocate their activities in the event of flooding. In the uplands where flash flooding is more frequent and violent, research is currently underway to establish whether this affects water vole survivorship in such areas.

There is no evidence that pollution is influencing water voles in North East Scotland. The main source of pollution is organic or nitrate leaching from agricultural land. As water voles are known to persist in waterways through very intensive farmland and areas of industrial development it is thought that this factor is unimportant as a threat. In urban or industrial sites, which are heavily disturbed water voles appear to be more tolerant of disturbance than some of their predators. To some extent this may allow water voles to survive better on waterways with regular disturbance, even in otherwise very poor habitat.

Even though water voles in North East Scotland are host to a vole-specific serotype of Weil’s disease (Leptospira interogans serotype saxkoeking), there is no evidence that this is detrimental to the species.

Interfering with water voles through active management such as translocation or captive breeding should only be seen as a last resort. With the presence of several strongholds in the NE action plan area, the actions outlined below are much more likely to have a real positive impact than active species management. Water voles are extremely fecund and very efficient at dispersing and will be able to naturally recover when the conditions are right.

4. CURRENT ACTION

There is no current conservation action in North East Scotland specifically targeted towards water voles. However, several riparian habitat improvement schemes have a beneficial impact on water vole habitat. These currently include the Ugie Wetland Project, the Ythan Project the NE Rivers Project, the Dee Habitat Enhancement Project and previously the FWAG Grampian Rivers Project. Current predator control activities being employed by landowners and farmers have a local beneficial impact by reducing predation pressure by mink.

At the UK level the Water Vole Action Plan Steering Group are currently identifying important sites. The group has also been involved in the production and promotion of guidance material on management for water voles, targeted towards land managers, planners and developers. Scottish Wildlife Trust have identified water voles as one of their priority species for action and are securing funding for a number of projects at sites with water voles.

5. BENEFITS

Implementing this action plan will help provide the conditions needed for the survival of water vole populations in the provisional ‘key areas’ in North East Scotland. Protection and enhancement of suitable habitat along waterways, will have benefits for associated species and for water quality. Survey and monitoring needed to implement this plan will add to our knowledge of the distribution of other potential key areas for water voles. Conservation action will provide working examples from water vole projects in both upland and lowland populations. Measures to mitigate the impact of mink on water voles will have an additional benefit for other riparian and fresh water species.

The objectives of the UK action plan are to:

• Maintain the current distribution and abundance of the water vole.
• Ensure water voles are present throughout their 1970s range by the year 2010, considering habitat management and possible translocation of populations to areas from where they have been lost.

In the NE re-establishing water voles throughout their 1970s range is not thought to be a realistic aim. The following objectives have therefore been adopted for the NE.

Identify ‘key areas’ still holding significant water vole populations in all North East catchments. Ensure survival of water vole populations in these identified ‘key areas’.

Target : No loss of water voles in identified ‘key areas’ by 2010.

Objective 1 : Identify ‘key areas’ with significant water vole populations.

Target : Areas identified by 2005

Objective 2 : Take immediate action to secure known upper Deeside and Ythan populations.

Target : Populations in upper Deeside and Ythan secured under co-ordinated management by 2003.

Objective 3 : Take action to secure additional ‘key areas’ identified.

Target : Additional key areas under co-ordinated management by 2005.

Objective 4 : Raise awareness of water vole conservation issues.

Target: Training and guidance available for landowners and advisory bodies by 2002.

Ensure that all relevant landowners and farmers are made aware of the presence of water voles on their land and of the legal implications, by 2001-ongoing.

Water vole integrated to catchment management plans, by 2001-ongoing.

Aars et al 2001.

Lambin at al 1996.

Lambin at al 1998.

Telfer 2000.

Reynold 2000

Lambin and Telfer (2001). North East LBAP Water Vole Action Plan. Detailed version, with further information on ecology, distribution and management recommendations.

DSFB-District Salmon Fisheries Boards, DevDSFB-Deveron District Salmon Fisheries Board, FWAG-Farming and Wildlife Advisory Group, HEI-Habitat Enhancement Initiative, HLF-Heritage Lottery Fund, LA-Local Authorities, LBAP-Local Biodiversity Action Plan, NERP-North East Rivers Project, NESBReC-North East Scotland Biological Records Centre, NFUS-National Farmers Union of Scotland, Rivers Pos-Rivers Project Officers, RSS-Rural Stewardship Scheme, SAC-Scottish Agricultural College, SEPA-Scottish Environment Protection Agency, SERAD-Scottish Executive Rural Affairs Department, SLF – Scottish Landowners Federation, SNH-Scottish Natural Heritage, UA-University of Aberdeen.