Water voles are the largest of the British vole species. They usually live beside water bodies where they feed on grasses and herbs growing on the banks where they dig their burrows. Scottish water voles are genetically distinct from those in the rest of the UK. The voles that colonised England and Wales following the last Ice Age originated from South East Europe, whereas Scotland’s voles appear to be descended from migrants from northern Iberia.
In lowland areas, water voles occur beside small slow-flowing burns, small backwaters, canals, ditch systems and overgrown field drains, sometimes in intensively-farmed and urban areas. The best sites support a continuous swathe of tall grassy vegetation top provide food and cover for the voles.
Due to desperate losses in the lowlands, water voles in Scotland are now mainly restricted to the smaller tributaries and headwaters of the rivers in the uplands. Here they are found in narrow moorland burns and barren peat hags on flat or gently sloping ground. Areas with a thick layer of peat and lush vegetation are preferred.
- 1 How is the water vole threatened?
- 2 How you can help
- 3 What needs to be done
- 4 About water voles
- 5 Water voles and the law
- 6 Assessing the impacts of developments
- 7 Mitigation
- 8 Conserving water voles – best practice
- 9 Contacts and further information
How is the water vole threatened?
The water vole is one of our most threatened native mammals, having undergone a dramatic decline, particularly during the latter part of the twentieth century. The reasons for this include habitat degradation and fragmentation, but also predation by American mink. Water voles have many native predators but, unlike the mink, none of these seem to threaten the survival of the water vole. Mink are waterside animals and female mink are capable of following the voles into their burrows.
How you can help
If you know of a water vole colony, you should make sure that it is known about – contact your local mammal recorder .
If you own or manage land, the guidance below may help.
What needs to be done
Water vole habitat can be damaged by reductions of the height of bankside vegetation due to grazing. But the growth of dense scrub or trees is equally damaging as it leads to a decline in the bankside grasses, reeds, sedges and rushes needed by the voles.
Water vole conservation relies on:
Maintaining tall grasses and herbs alongside the water body. Fencing may help although the growth of young trees and scrub needs to be prevented.
Minimising the opportunity for mink colonisation (including habitat management to reduce the opportunities for denning, targeted mink control and rabbit control if required.)
About water voles
The water vole, or ‘water rat’ as it is often mistakenly called, was formerly one our most familiar and abundant riverside mammals. Sadly, it is now one of our most threatened native mammals. The species has undergone a dramatic decline, particularly during the latter part of the twentieth century and voles have been lost from many areas where they were formerly common. The decline is correlated with the spread of introduced American mink (Neovison vison) and there is abundant evidence that mink predation is a major cause of water vole mortality in many areas. However, as the decline started well before mink became widely established, it is clear that habitat loss, fragmentation and degradation is also a problem. The mink may simply have been the last straw.
The water vole is the largest of the British voles with many Scottish animals having black fur rather than brown, which is more typical elsewhere.
Where do they live?
In lowland areas, water voles are now most likely to be found in small slow-flowing or static burns, backwaters, canals, ditches and overgrown field drains, sometimes in intensively-farmed and urban areas. These watercourses are usually less than 3 m wide and 1 m deep and do not show extreme fluctuations in water level. Water voles prefer sites with steep (>35º) or stepped bank profiles into which the vole can burrow and create nest chambers above the water table. Soft, easily excavated soils are preferred. The amount of bankside and emergent vegetation cover is very important, with the best sites offering a continuous swathe of tall and luxuriant riparian plants. Sites excessively shaded by shrubs or trees (>20% bankside tree cover) are less favoured.
In the uplands, voles are able to survive in narrow moorland burns on flat or gently sloping ground (average gradient no more than 3%)with extensive thick deposits of peat. Such conditions may be encountered near the headwaters of a river system or in the upper reaches of a glaciated valley where a small burn meanders across a high altitude marshy floodplain. Here, conditions are often suitable for stands of the water vole’s preferred food, i.e rushes and sedges.
In many areas, particularly in the lowlands, habitat loss and fragmentation have contributed to the decline. These effects have resulted from damaging riparian management, such as over-zealous or ill-considered vegetation cutting and ‘hard’ river engineering techniques such as canalisation and culverting long stretches of watercourse. In many lowland pastoral areas over-grazing can be problem, resulting in close-cropping of the bankside vegetation and poaching of the riverbank. Conversely, an absence of grazing or manual control of the bankside vegetation can be equally detrimental over time. The growth of dense thickets, uncontrolled scrub and trees leads to a decline in the bankside grasses, reeds, sedges and rushes so favoured by the voles.
Water voles are preyed upon by a range of native predators, but unlike the introduced American mink, none of these seem to influence water voles at the population level. Female mink are smaller than males and are easily capable of following the rodents into their burrows. As the two species are both usually found close to water, they are much more likely to encounter one another than are water voles and, say, stoats or weasels. A female mink with kits to feed is potentially, therefore, a major threat to any nearby water vole colonies. The threat posed by mink applies over most of the water vole’s range, although in upland areas mink tend to be scarce or absent allowing the water voles to persist.
As a result of these pressures, in many river systems, water voles are now as absent from most of the main stem and the larger tributaries, being restricted to the headwaters and smaller tributaries in the upper or peripheral parts of the catchment.
Water voles and the law
Water voles are listed on Schedule 5 of the Wildlife & Countryside Act 1981 (as amended). In Scotland, the legal protection associated with this listing is currently restricted to the water vole’s places of shelter or protection and does not extend to the animals themselves. However, full protection covering the animals themselves is proposed.
At present it is an offence to intentionally or recklessly:-
- Damage, destroy or obstruct access to any structure or place which water voles use for shelter or protection, and;
- Disturb water voles while they are using such a place.
The Law in Practice
It is not the intention of the law to prevent all activities in areas used by water voles. However, legal protection does require that due attention is paid to the presence of voles and appropriate actions are taken to safeguard the places they use for shelter or protection.
There is a defence against prosecution if it can be shown that the unlawful act was “the incidental result of a lawful operation or other activity” and that “the person who carried out the lawful operation or other activity took reasonable precautions for the purpose of avoiding carrying out the unlawful act” or that the person “did not foresee, and could not reasonably have foreseen, that the unlawful act would be an incidental result of the carrying out of the lawful operation or other activity”. This defence only applies if the person stops causing any further illegal actions as soon as practically possible once he or she realises they are occurring.
In some cases licences may be issued by Scottish Natural Heritage to enable certain otherwise illegal activities to take place. With respect to development-related activities, licences can be issued where there is likely to be damage to a water vole burrow, or disturbance to a water vole within its burrow, for social, economic or environmental reasons. Licences may only be issued for this purpose provided that:
- the activity authorised by the licence will contribute to significant social, economic or environmental benefit; and,
- there is no other satisfactory solution.
Further details are available in Licensing.
Assessing the impacts of developments
Water voles and the planning system
Planning authorities are required to take account of protected species and habitat conservation when they consider planning applications, see Scottish Planning Policy . Where water voles are present or likely to be present, the planning authority may require a survey to be undertaken, paid for by the developer. If water voles are likely to be affected, the planning authority may introduce planning conditions and/or agreements when determining individual applications.
Water vole surveys
There are two ways to find out whether there are water voles on site:-
- desk-based collation of known records
- site-based survey
The desk-based study should review records of water voles from sources such as Local Record Centres or the NBN Gateway . Note that the dramatic decline in water voles means that many older records (i.e anything much older than the Year 2000) must be treated with caution as they are unlikely to reflect the present situation, especially in lowland areas.
A field survey should be based on the presence of characteristic field signs such as burrows, feeding stations, runs, tracks, droppings and latrines. Site-specific searches, by an appropriately experienced surveyor, should involve a close examination of all waterway and pond banks up to two metres from the water’s edge. The presence of signs should be recorded on a detailed map. Although they do not hibernate, water voles are not very active above ground during the winter, so surveys are best carried out between April and October. In upland areas, surveys are not recommended before May or after September, the optimum months being June-August inclusive. See the Water Vole Conservation Handbook (3rd edition) for further details of field signs and survey methods.
Note that because of the water vole’s meta-population structure, sites may not be occupied in every year. Therefore, it cannot be assumed that the presence of burrows but no other field signs indicates that a site has been permanently abandoned – if there are extant colonies nearby, such sites may easily be re-occupied.
With the exception of those areas initially eliminated as unsuitable for water voles, the whole of the development site should be surveyed. For small sites, an extra 50m upstream and downstream of the development should be surveyed. For larger schemes affecting several 100 metres (or kilometres) of riparian habitat that result in noticeable water level fluctuations and may lead to population fragmentation and habitat loss, it would be appropriate to survey for 500m both upstream and downstream of the site.
IMPORTANT NOTE: water vole surveys in the Glasgow area
Glasgow contains some of the best water vole populations in lowland Scotland. Many of these colonies are in areas of rough (but managed), urban grasslands but with no open water anywhere nearby. The water voles at these sites create extensive burrow systems, but also forage extensively above ground in a manner similar to field voles (Microtus agrestis), creating latrines, earth mounds and runs through the vegetation. On the face of it, most of these sites might easily be immediately discarded as potential water vole habitat due to the complete absence of open water and the apparently poor quality habitat. It is important therefore, that developers, planners and, in particular, ecological consultants, are aware of this unusual fossorial behaviour in the area, because many of the areas occupied are zoned for development, notably new housing. Appropriate surveys of such areas are therefore needed to inform the mitigation plans required for planning permission and in support of a licence application at each site.
Guidance on water vole surveys in relation to proposals for hydro-electric development is given in Annex C of Guidance for applicants on supporting information requirements for hydropower applications. This approach may be adapted for other forms of development affecting upland catchments, as appropriate.
Where development may affect water voles or their habitats, consideration should be given to the following courses of action:
Planning the development to avoid water vole habitats
This is the preferred course of action. As water voles confine most of their activities to within a few metres of water it may be possible to leave undeveloped areas around ponds or wildlife corridors along ditches or streams. These corridors have an additional important function of linking together water vole populations and are recognised as a useful contribution to nature conservation.
Exclusion from development areas
The careful removal of surface vegetation from small areas to be developed (e.g. road or pipeline crossings) can cause water voles to move to nearby alternative areas, provided these are suitable and not already occupied by voles. During the growing season, green shoots should be removed at frequent intervals to discourage the voles from returning. This method is most likely to be successful early in the year (before the females have dependent young) and over short lengths of bank. In practice, this window of opportunity is restricted to March and perhaps early April. A licence from Scottish Natural Heritage is likely to be required for this work.
Trapping and translocation
This is regarded as the least preferable option and should only be attempted where there are no alternative options available and no other practical solutions which would allow water voles to be retained at the same location.
Development can sometimes provide opportunities for habitat enhancement by restoring degraded habitats and encouraging the return of a greater range of wildlife. For water voles, the restoration of vegetated bankside corridors to link fragmented populations could help to reverse local population declines or improve the viability of small populations. An ecological appraisal should identify such opportunities for positive works. Wherever possible, favourable management for water voles should be promoted through the adoption of a habitat management plan.
In addition to measures designed to protect and enhance the quality of the existing riparian habitat, the creation of new wetland habitat in the form of new SUDS ponds, extra lengths of waterway or even the manipulation of the flow regime to create better conditions for water voles can be all be highly beneficial in the right circumstances. As water voles occupy linear territories, maximising the sinuosity of a narrow watercourse, by creating a series of tight meanders instead of a short straight canalised section creates a considerable amount of extra vole habitat which can support a much higher vole population. In some cases, a short section of fast-flowing narrow burn in otherwise ideal water vole habitat could be slowed-down with the construction of a small weir to form pools or areas of slow-flowing water that are of more benefit to the voles.
Further detail on some of the above can be found in the Water Vole Conservation Handbook (3rd edition).
Any works that are likely to damage a water vole burrow or disturb a water vole within it will require a licence from Scottish Natural Heritage. A licence to disturb water voles may be required for any works proposed within 10m of an active water vole burrow, even if no physical damage to the burrow or its immediate vicinity (i.e the riparian strip 5 metres in from the water’s edge) will occur. See Licensing for further information.
Conserving water voles – best practice
Because of the population dynamics and dispersal behaviour of water voles, the protection of individual colonies in isolation is unlikely to achieve any lasting conservation benefits. Instead, a strategy that considers a number of nearby populations together is, realistically, the only way likely to ensure long-term persistence. The basic principles for conserving water voles can be summarised thus:-
- Maintain habitat connectivity between individual colonies and minimise the degree of isolation between adjacent vole colonies, such that occupied sites are within a 1.5 km radius of one another
- Maintain abundant herbaceous riparian vegetation (including the management of trees to avoid excessive shading)
- Minimise the opportunity for mink colonisation (including habitat management to reduce the opportunities for denning, targeted mink control and rabbit control, as appropriate)
In the uplands
In upland river systems, conservation effort should be directed at extensive catchment or multi-catchment scale areas.
- Good quality upland water vole habitat comprises sedge-rich areas, including grasses, rushes and heather adjacent to slow flowing, shallow burns with steep peaty banks. These areas are also likely to be favoured by deer and sheep and may, in some cases, be vulnerable to excessive grazing and poaching. Stock reduction may therefore be required to prevent this.
- Where they include areas of suitable water vole habitat new native woodland schemes will need to incorporate suitable riparian corridors.
- Avoid muirburn in areas of suitable water vole habitat. An unburnt buffer strip of at least 10 m on each side of any watercourse used by water voles is required to protect the voles’ habitat.
- Constant vigilance is required to prevent mink colonisation of upland river catchments. This could be achieved by targeted and co-ordinated trapping effort concentrated at critical times (February to April) and at critical sites (e.g. the tributaries leading to these upland catchments).
- The presence of rabbits may encourage the spread and establishment of mink in the uplands by providing a reliable food source and potential breeding sites. This can enable permanent rather than transitory colonisation by mink. Measures may therefore be needed to prevent the spread of rabbits into such areas.
In the lowlands
Here, water voles are best protected from excessive grazing of riparian habitats by the creation of a fenced-off buffer strip either side of the water course. Ideally, these strips should be 6 m wide on both sides of the watercourse. Scrub encroachment should be prevented by occasionally cutting all this vegetation back to around 10-15 cm during the autumn/winter. In some lowland river catchments, overgrown field drainage ditches are important refuges for water voles. It is recommended that clearance and dredging of these is undertaken on a 5-10 year rotation. As dredging usually necessitates the removal of bankside vegetation, it is better to cut this in September/October, prior to any excavation work, allowing water voles to move away from the area, prior to the earthmoving operations.
- Avoid re-profiling both banks in any one section.
- Progress upstream leaving sections of untouched habitat at least 250 m in length.
- Keep the length of each dredged section to a minimum; if possible, no longer than 150 m.
- Only operate machinery from one bank (i.e the opposite bank should remain completely untouched).
- Only dredge during the winter months.
Further detail on this can be found in the Water Vole Conservation Handbook (3rd edition).
Contacts and further information
Capreolus Wildlife Consultancy (2005). The ecology and conservation of water voles in upland habitats . Scottish Natural Heritage Commissioned Report No. 099 (ROAME No. F99AC320).
Ed. Jefferies, D.J. (2003) The Water Vole and Mink Survey of Britain 1996-1998 with a history of the long-term changes in the status of both species and their causes. The Vincent Wildlife Trust.
Highways Agency: Design Manual for Roads and Bridges. Volume 10. Nature Conservation Advice in Relation to Water Voles. (Under revision and not currently available).
Macdonald, D. & Strachan, R. (1999) The Mink and the Water Vole: Analyses for Conservation. (Environment Agency/WildCRU).
Newton, J., Nicholson, B. & Saunders, R. (2011) Working with wildlife: guidance for the construction industry (C691). CIRIA.
Iuell, B., Bekker, G.J., Cuperus, R., Dufek, J., Fry, G., Hicks, C., Hlavac, V., Keller, V., B., Rosell, C., Sangwine, T., Torslov, N., Wandall, B. le Maire, (Eds.) 2003. COST 341 – Wildlife and Traffic: A European Handbook for Identifying Conflicts and Designing Solutions.
Scottish Environment Protection Agency (2000) Ponds, pools and lochans. Guidance on good practice in the management and creation of small waterbodies in Scotland.
Scottish Environment Protection Agency (2010) Guidance for applicants on supporting information requirements for hydropower applications . The Water Environment (Controlled Activities) (Scotland) Regulations 2005 (CAR)
Scottish Planning Policy
Strachan, R. (1997) Water Voles. Whittet Books.
Strachan, R., Moorhouse, T. & Gelling, M. (2011) Water Vole Conservation Handbook. Third Edition. Wildlife Conservation Research Unit, Oxford.