Water voles, like almost all our other declining species, are being lost as a result of human actions. Habitat loss, water pollution and predation by invasive non-native American mink have pushed this endearing river resident to the brink of extinction across the UK.

Water voles are mini ecosystem engineers and their return will see, in part, the restoration of natural processes to rivers. Water voles keep river banks in good condition and are a vital part of the animal food chain.

At Herts and Middlesex Wildlife Trust, we want to see water voles thriving in every river across the county. To achieve this goal, we need to execute numerous reintroductions of the species. 

How do species reintroductions work?

1. Find the habitat

To plan a species reintroduction, the first thing to do is find a suitable habitat. Whatever the species, for the reintroduction to be successful, the animals will need sufficient food, shelter and to be reasonably safe from predators. For water voles, suitable habitats are usually rivers with plenty of vegetation which allow the voles to feed and hide from birds of prey and mammals which like to eat them.

Fact: water voles are humorously known as ‘nature’s chocolate biscuit’ due to the high number of animals that find them delicious and easy to hunt.

2. Make sure the habitat is safe

After a habitat has been found, surveys are conducted to ensure the species will survive its reintroduction. This process may involve controlling the local population of predators. In the case of water vole reintroductions, conservationists remove American mink to improve the voles’ chances of survival.

Fact: American mink are a non-native species in the UK and were brought over in the 1920s for the fur trade. To read more about American mink, visit our wildlife explorer page.

3. Find the species 

Once a habitat has been identified and made safe, conservationists source the species they hope to reintroduce. Sourcing wild species can happen in two ways:

1. Finding a licensed breeder to breed the species specifically for the reintroduction
2. Capturing and moving a portion of the wild species from one location to another. This process is called translocating. 

Conservationists often find a licensed breeder for an initial reintroduction and then use the translocation method for future reintroductions to spread the population of the species. 

4. Release the species

When the hard work of planning has been completed, conservationists release the species into the chosen habitat. There are numerous ways to do this. Some species are placed through a ‘hard’ release which simply means to place the animal in the chosen habitat and allow them to naturalise. In other instances, a ‘soft’ release takes place which involves creating temporary homes such as pens that are left in the habitat for the species to acclimatise to its new environment.

Fact: The jury is still out on whether there are any benefits in using the two release methods, though the British Ecological Society published an article that argued that soft releases tend to be more successful in reptile reintroductions (source).

5. Monitor the species

The final stage in executing a reintroduction is monitoring the species once the release has been completed. This often takes place in the form of regular surveys in which conservationists record sightings or signs of the species at the reintroduction site.

Fact: To monitor water vole reintroductions, conservations look for their uniquely shaped faeces which are shaped like tic tacs! 

Our water voles back on the Ver

In the Trust’s most recent reintroduction of water voles on the River Ver, funding was generously provided by The Debs Foundation and the Linder Foundation to source the voles from specialist breeders. On the day of release, volunteers from the Ver Valley society lent a helping hand to set the soft release pens up for the voles to live in before finally making a home on the river.

Water voles are part of a wider decline in our wild species and habitats across the UK. In Hertfordshire, one-fifth of the wildlife assessed in Hertfordshire’s State of Nature Report, published by the Trust in 2020, is currently either locally extinct or threatened with extinction. Habitat loss and fragmentation have sent populations plummeting. The report concluded that at least 30% of land in the UK must be protected for wildlife to combat the ecological and climate crisis.

Watch the reintroduction of water voles to the River Ver with Josh Kalms, water vole conservation officer.