Southern water vole  (Arvicola sapidus)

The southern water vole is classified as Vulnerable (VU) on the IUCN Red List (1).

A rare, threatened vole of Iberia and France (1), the southern water vole (Arvicola sapidus) is a small, thickset rodent with a bluntly rounded muzzle, small eyes and small ears (3). The head is relatively long, and the forelimbs are longer than those of most other voles and lemmings, but still only protrude slightly from the thick fur. The coat is dark brown to black, and is slightly lighter on the underparts. The tail is covered in short, stiff, sparse hairs (2). 

The southern water vole was once considered a subspecies of the European water vole (Arvicola terrestris). However, it is now considered a separate species, in part due to significant morphological differences (4). Some recognise two subspecies of the southern water vole: Arvicola sapidus sapidus and Arvicola sapidus tenebricus. A. s. tenebricus is dark to reddish brown, while the coat of A. s. sapidus is generally lighter and more yellowish (1). However, others do not believe that the differences between these two forms of the southern water vole warrant subspecies status (5).

The southern water vole occurs only in parts of France and Iberia (Spain and Portugal). In France, it remains relatively common in only three regions: Charente-Maritime, Brittany and southwest France, although it has a rather patchy distribution in these areas.

In Spain, the southern water vole is now restricted to the northern and eastern parts of the country, and has disappeared from central Spain, where it was formerly common. The distribution of the southern water vole is not well documented in Portugal, but it is thought to occur in isolated fragments in only a few parts of the country (1). 

Arvicola sapidus sapidus occurs in Portugal and southern Spain, and Arvicola sapidus tenebricus is found in France and northern Spain (1).

Occurring at elevations between sea level and about 2,300 metres, the southern water vole is almost always found near to water, preferring small freshwater lakes, ponds and slow-moving rivers, and streams with dense riparian vegetation. It sometimes also occurs in drainage ditches and wet fields (1).

The southern water vole is active during the day, with peaks of activity in the late morning and early afternoon. It is sometimes also active at night, but typically resides in its burrow after daylight. The burrows of the southern water vole usually have two entrances: one primary entrance above water level and one underwater entrance. Its diet consists mainly of aquatic plants, grasses, and herbs, although small animal prey is occasionally taken, such as insects, fish, tadpoles and freshwater shrimp (1). The southern water vole does not hibernate and is active year-round (1), taking shelter in its burrow during periods of harsh weather (3).

Restricted to wetland areas, and flourishing only where the banks and vegetation have not been significantly altered by human activity (6), the southern water vole is at risk from habitat loss and disturbance by human activity. This species has rapidly declined across most of its range and now only occurs in small fragments, primarily as a result of habitat loss from drainage, dredging, canal-building, infrastructure development and intensive agriculture. Competition with the introduced coypu (Myocastor coypus) and muskrat (Ondatra zibethicus) for food and dens is also a threat, while in Spain, competition with the brown rat (Rattus norvegicus) may be an additional factor threatening the southern water vole (1). 

These threats have been compounded by accidental poisoning from chemicals used to kill invasive species, as well as by a general lack of information on the distribution and status of this species. Until relatively recently, a significant decline of the southern water vole in France had gone largely unnoticed, primarily due to a lack of survey work, but it is now known to be much less common that it was 10 to 15 years ago. There is also a particular lack of knowledge of the status of this species in Portugal (1).

In recent decades, the southern water vole has received relatively little attention compared to other mammals within its range, and, consequently, its demise has almost gone unnoticed. This makes further research and monitoring of this species absolutely critical. Furthermore, as it does not yet receive any European or national legal protection, protecting this species under legislation such as the EU Habitats Directive would be of great benefit to this species and would also increase awareness of its fate (1). 

Other conservation recommendations for the southern water vole include preventing the use of rodenticides in habitats occupied by this species, measures to prevent the further introduction or spread of invasive species and regulation of the management of waterways such that the welfare of wildlife is considered. A captive breeding programme may also allow captive-bred individuals to be released to augment existing wild populations (1).

Find out more about habitat protection in Europe:

• Natura 2000 Networking Programme:
  http://www.natura.org/