The water vole, scientifically known as Arvicola amphibius, is a medium-sized rodent recognized for its semi-aquatic lifestyle along the waterways of Europe and Asia. This mammal is an important part of riparian ecosystems, playing a role in managing bankside vegetation through its feeding habits. The water vole’s existence is closely tied to freshwater environments, making it a reliable indicator of the health of rivers, streams, and ditches.
Physical Characteristics and Identification
The water vole possesses a distinct morphology that sets it apart from other small mammals, particularly the brown rat. Its body is rounded, and its head features a blunt, wide muzzle. Adults typically weigh between 200 and 350 grams and measure approximately 29 centimeters, making it one of the largest voles.
A key identifying feature is the presence of small, rounded ears almost completely hidden within its thick, dense fur. Unlike the hairless tail of a rat, the water vole has a relatively short, hair-covered tail. The coat color is usually a rich mid-brown to reddish-brown, though individuals in upland regions can exhibit melanism, resulting in a black coat.
Preferred Habitats and Distribution
The water vole is widely distributed throughout the Palearctic region, spanning much of Europe, Russia, and parts of Asia. Its presence is dictated by the availability of suitable environmental conditions. The species prefers still or slow-moving water bodies, such as ditches, streams, ponds, and smaller rivers.
The preferred habitat must include dense, lush vegetation along the banks, which provides both food and cover from predators. The banks also need to be composed of deep, earthy material that the vole can easily excavate to construct extensive burrow systems. Water voles avoid areas with heavy tree cover or concrete-lined banks, as these environments do not allow for stable burrow construction.
Diet and Behavioral Adaptations
The water vole is primarily herbivorous, with its diet consisting almost entirely of riparian vegetation. It consumes a wide variety of plants, including grasses, sedges, and rushes, often leaving behind distinctive piles of nibbled stems cut at a 45-degree angle. During winter, the vole supplements this diet by feeding on roots, bulbs, and woody material.
As a semi-aquatic species, the water vole is an excellent swimmer and diver, often plunging into the water to escape danger. It is most active during the day, particularly around dawn and dusk. The animal constructs complex burrow networks within earthen banks, featuring multiple entrances, including some situated below the water line for concealed entry and exit.
The species is territorial, and adults mark their range using a secretion from flank glands and by depositing piles of droppings known as latrines. These latrines are typically found at favored feeding spots or near the water’s edge, serving as communication for other voles. Inside the burrows, the voles maintain chambers for nesting and storage, often hoarding food supplies for the winter.
Conservation Status and Population Threats
While the water vole is classified as Least Concern globally, it faces severe threats in many regions, including the United Kingdom, where it is considered one of the most rapidly declining mammals. The species has suffered significant population losses, with some areas reporting declines of over 90% in recent decades.
The decline is primarily driven by the loss and fragmentation of wetland habitat due to changes in land management and agricultural practices. The most severe threat comes from the non-native American mink, an invasive predator introduced through fur farming. The mink is a strong swimmer and small enough to follow voles directly into their burrows, proving devastating to water vole colonies.