The very first stretch of river we survey for water voles, early in my Ecology Traineeship, is the perfect place to learn the ropes. Guided by Lucy, the Mammal Project Field Officer, we find plenty of signs.

Clumps of greenish, sausage-shaped droppings the size of tic-tacs (known as latrines), sometimes positioned prominently on tree roots near the water’s edge. They smell inoffensively of freshly cut grass when broken open. I have since learnt that this is not the case with rat droppings.

There are also plenty of footprints, running in tracks along the soft mud of the riverbank. They are very similar to rat prints, but are generally smaller and more splayed and star shaped when you find a clean one. There are burrows as well: some are made by field voles, rats or signal crayfish, but there are also the distinctive round, tennis ball sized burrows of water voles.

Another thing we look for are feeding signs. Water voles eat grass and other vegetation, leaving discarded stems in piles, helpfully nibbled at a distinctive 45-degree angled cut. Once you get your eye in you start to notice them, and while today it is spring and there are not many feeding signs at this time of year (they like the new growth and are less picky about what they leave behind), we do find some.

It’s an excellent first day. But, as we walk back to the car along a farm track, Lucy spots something in the soft earth: a single mink print. It’s rare to find signs of mink and to see this print so close to the river where we know there are water voles is concerning.

The water vole is Britain’s fastest declining mammal, losing 95% of its range over the last hundred years. This is partly due to habitat loss, but more recently by the introduction of the non-native American mink. Mink were brought to the UK for fur farms in the 1920s, and by the 1950s they were breeding in the wild, having either been released or escaped. They are now widespread throughout most of the UK.

Water Voles have their own native predators in the UK: foxes, pikes, owls and herons to name a few. The water voles usual defence is to retreat inside their burrows. However, female mink can fit inside water vole burrows and can wipe out entire colonies in a relatively short period of time.

BBOWT’s Water Vole Recovery Project monitors water vole numbers in the three counties and gives advice to landowners to manage waterways more sympathetically for water voles and implementing mink control. For us trainees, this means surveying 500m stretches of rivers, brooks and ditches, looking for signs and mapping out the habitats we find along the waterways.

Since that first survey, Sam (my fellow Ecology Trainee) and I have spent roughly one day a week looking for signs of water voles. We have been lucky enough to visit some beautiful stretches of river: some within reserves and others on private land where it feels mostly untouched by humans.  

Other surveys have taken us to less picturesque places, but there are surprises here as well: we have found water voles living in tiny ditches alongside major roads and bordering supermarket car parks.

As the months have passed into summer, it hasn’t always been easy going. The vegetation has grown tall and thick, and surveys require pushing through dense thickets of bramble and nettle to reach the riverbank. Some channels are choked with reeds which makes for slow progress, and it can get quite warm inside a pair of waders on a summer’s day.  

But there’s nothing quite like nearing the end of a difficult stretch of river that has so far revealed no signs, only to find a burrow or a well-hidden latrine just before the survey’s end.

There have been plenty of other things to see on our days on the river: nesting kestrels and tawny owls, snipe, curlew, cuckoos and moles. There are signs of other mammals as well, including polecats and otters. Otters seem to be abundant on the waterways we have surveyed. Their numbers have been increasing throughout the UK and I would say that on the vast majority of our water voles surveys we have found signs of otters.

The future of water voles in the UK is more precarious. In 2018 the National Water Vole Mapping Project suggested water vole presence had declined by 30% between 2006 and 2015 across England and Wales.  

I’ve seen myself how a stretch of river that yielded hundreds of water vole signs only a few years ago has this year shown no signs of their presence at all. In this case, recently introduced livestock have trampled the riverbanks to nothing, with nowhere for water voles to burrow and no vegetation left to eat.

But there are positives as well.  BBOWT’s Water Vole Recovery Project seems to be making an impact in the three counties, where known water vole sites have been increasing in contrast to the national decline. In 2008 the total area of water vole activity in the three counties stood at 321km², this increased by 78% over the last 10 years to reach 603km² in 2018. Already this year we have found evidence of water voles on some stretches of river where previous surveys have found none.  

But despite all the time we have spent on the river, we are yet to actually see a water vole in the flesh.

We’ve come close, hearing the tell-tale ‘plop’ of a water vole diving into the water. I’m told that some trainees go the full year of their traineeship without ever seeing one. It remains to be seen whether I will be counted among them, but in the meantime, I’m enjoying putting on my waders and searching for latrines amongst the reeds.

Dave Dunleavy, ecology trainee

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