The water vole, often mistakenly identified as a common brown rat, is a native British mammal with a distinct place in the country’s riverside ecosystems. This semi-aquatic rodent plays a role in maintaining the health of waterways. Despite once being a common sight, its presence has significantly diminished across its historical range.
Identifying a Water Vole
Distinguishing a water vole from a brown rat involves observing several key physical traits. Water voles have a rounded face, blunt nose, small ears hidden in fur, and a furry tail about half their body length. Their fur is typically chestnut-brown, though some Scottish populations are black. Brown rats, conversely, have a pointed nose, larger ears, and a long, scaly, largely hairless tail often as long as their body.
Adult water voles measure approximately 14-22 centimeters in body length, with their tails adding another 9.5-14 centimeters, and they weigh between 150-300 grams. Their appearance is plump and rounded, unlike the leaner, more elongated body of a brown rat. When swimming, a water vole’s body is quite buoyant, with a significant portion remaining visible above the water surface, whereas a brown rat tends to swim with only its head showing.
Beyond physical appearance, other signs can help confirm a water vole’s presence. Their burrows, found in riverbanks, are wider than they are high, about the size of a tennis ball, and may have a “lawn” of neatly cropped grass around the entrance. Water voles also leave distinct, tic-tac shaped droppings in communal piles called latrines near the water’s edge. These droppings are green, brown, or black and lack the foul odor associated with rat droppings.
Life in and Around Water
Water voles thrive in environments with slow-flowing water and dense bankside vegetation, such as rivers, streams, ditches, and the edges of ponds and lakes. They construct intricate burrow systems within soft, earthy banks, with multiple chambers for nesting, sleeping, and raising young. These burrows feature at least two entrances, one on the bank and another submerged underwater, providing a quick escape route from predators. They create distinct “feeding stations” where they sit and eat, leaving behind piles of chewed vegetation with characteristic 45-degree angled cuts on the stems.
As herbivores, water voles primarily consume plant material, including grasses, sedges, rushes, and other waterside vegetation. They require a substantial amount of food, eating up to 80% of their body weight daily. While their diet is predominantly plant-based, lactating females or those in need of protein may occasionally supplement their diet with molluscs or small fish. Water voles are active during the day, spending their time foraging, swimming, and maintaining their burrows.
Their breeding season runs from April to October, with females producing multiple litters (three to six) each year. Each litter consists of three to five pups, which are born blind and hairless. These young voles grow rapidly, leaving the nest after about three weeks and becoming capable of breeding themselves within 15 weeks. Despite their high reproductive rate, water voles have a short lifespan in the wild, many not surviving beyond their first winter.
Conservation Concerns
The water vole is a threatened native mammal in the UK, having experienced a population decline of over 90% since the 1970s. This reduction has led to its classification as Endangered on the UK Red List. Several factors contribute to this decline, with habitat loss and fragmentation being major threats. The destruction of riverside vegetation, river engineering, and agricultural practices diminish and isolate suitable living areas for these animals.
A major cause of the water vole’s decline is predation by the non-native American mink, an invasive species that escaped from fur farms and established wild populations in the UK. Unlike native predators, which water voles have evolved defenses against through high birth rates and burrowing, female mink are slender enough to enter water vole burrows, often eliminating entire families. This predatory advantage makes mink a significant threat to water vole colonies.
Conservation efforts aim to reverse this trend and protect the remaining water vole populations. The species is legally protected under the Wildlife and Countryside Act 1981 in the UK, making it an offense to intentionally kill, injure, or disturb them, or to damage their burrows. Conservation strategies include habitat restoration, such as maintaining dense bankside vegetation and ensuring soft, burrowable banks. Additionally, targeted American mink control programs are in place to reduce predation pressure and allow water vole populations to recover in specific areas.