An introduction to the NWVMP

Water voles have undergone one of the most serious declines of any wild mammal in Britain during the last century. The intensification of agriculture during the 1940s and 1950s caused the loss and degradation of their habitat but the most rapid period of decline was during the 1980s and 1990s as the numbers of illegally released American mink spread across the countryside.

+ Past water vole surveys and conservation work

The Vincent Wildlife Trust conducted two national water vole surveys in 1989-90 and 1996-98 which clearly demonstrated the massive decline in water voles across Britain. During each of these surveys 1,926 randomly selected baseline sites and 1,044 sites that had historically had water voles were surveyed for water vole field signs.

The 1989-90 survey found water voles were present at 1,418 sites (47.74%). However, by the time the sites were surveyed again between 1996-98 the number of positive sites had crashed to 461 (15.52%). The water vole population was estimated to have experience an overall loss of 88% over seven years.

Following these two surveys there was a concerted effort to monitor water voles, restore habitat along waterways, control the invasive mink population, as well as release captive bred water voles back into historic sites.

However, until now there hasn’t been a national monitoring programme to bring together all current monitoring and establish monitoring of sites across England, Scotland and Wales to determine the distribution and relative abundance of water voles on an annual basis – and that’s where we need your help.

The National Water Vole Monitoring Programme (NWVMP) aims to resurvey a sample of these historical sites, as well as bring together all current monitoring, to allow us to detect what changes have occurred since 1998. By monitoring these sites year on year we will be able to fine tune our conservation efforts.

+ Choosing a site to survey

Once you have successfully registered, you will be able to select a site to survey. If you are already monitoring a site, then you will be able to register this site with the programme.

Each year we will ask you to survey your site between 15th April and 15th June and submit your data, whether you detected water vole field signs or not.

Pre-selected sites

We have carefully selected nearly 900 sites across England, Scotland and Wales that were surveyed during the two Vincent Wildlife Trust surveys. It is really important to go back to these original sites to get robust data on how the population of water voles in the UK is faring.

You will be able to select one of these sites by entering your postcode/town on our online Google map. After you have selected a site it will no longer be available for another volunteer to choose.

Next, you will need to visit your chosen site in advance of the survey. This will enable you to fill in the site information form, gain permission to enter any private land and plan and map the route of your 500m transect.

Add a new site you already survey

If you are already monitoring a site for water voles, you can register your site with the survey once you have signed up online. Each site should ideally have a continuous 500m transect that can be surveyed annually to tie in with the other sites that will be surveyed. However, if this is not possible then a shorter transect (any denomination of 100m) can be surveyed and multiple transects at each site can also be included.

We would also encourage you to take on one of the existing sites too so that we can try and get as many of these sites monitored each year.

Please note that to register a site that you are already surveying, you will need to know:
• The grid reference of your site
• The county your site is in
• The name of your site .e.g. River Avon
• Habitat of the site and waterway type
• Number of transects at the site
• Whether mink are controlled at the site

Once you have successfully registered your site, you will be all set to do your survey between 15th April and 15th June.

UK Grid References

The National Grid system covers Great Britain with 100km grid squares.

Each 100km grid square in England, Scotland and Wales is identified by 2 letters e.g. TL.

Each 100km grid square is further divided into smaller squares by a set of grid lines representing 10 km spacing, each numbered from 0-9 from the south west corner, in an easterly (left to right) and northerly (upwards) direction e.g. TL63

Always remember to read grid references by eastings first (left to right) and then northings. If you have trouble remembering say along the hall, then up the stairs.

1km survey site

Each 10km square is then further divided into 1km squares, which are reference by a four figure grid reference, eg TL 6532 which is made from putting the eastings together (6 along for the 10km square and then five for the 1km square) and then the northings.

Each 1km square is then further divided into 100m squares (which are referenced using a six figure grid reference) and 10m squares (given by an eight figure grid reference).

Your site will have an eight figure grid reference that indicates its location.

You can find out more information about using grid references at

Download a printable version of these guidelines:

Next: Planning your survey

Training menu:

An introduction to the NWVMP
Planning your survey
Searching for field signs
Carrying out your survey
After your survey
More training links

Feedback – we would really value your feedback on these training pages and also on the monitoring programme. Please email any comments to

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