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Arvicola sapidus

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA RODENTIA CRICETIDAE

Scientific Name: Arvicola sapidus
Species Authority: Miller, 1908
Common Name(s):
English Southern Water Vole, Southwestern Water Vole
French Campagnol Amphibie, CAMPAGNOL AMPHIBIE
Spanish Rata De Agua, RATA DE AGUA
Taxonomic Notes: There are two subspecies of the water vole: Arvicola sapidus sapidus (Miller, 1908) and Arvicola sapidus tenebricus (Miller, 1908). A. s. sapidus is present in Portugal and southern Spain, while A. s. tenebricus occurs in France and northern Spain. A. s. tenebricus is dark to reddish brown, while the coat of A. s. sapidus is generally lighter and more yellowish (Noblet 2005).

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2ace+4ace ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Rigaux, P., Vaslin, M., Noblet, J.F., Amori, G. & Palomo, L.J.
Reviewer(s): Amori, G. (Small Nonvolant Mammal Red List Authority) & Temple, H. (Global Mammal Assessment Team)
Justification:
The water vole has undergone a marked reduction in both the absolute number of individuals and its subpopulations located throughout its traditional range in France, Spain and Portugal, and that this decline is continuing as a result of ongoing habitat modification/disturbance and competition with introduced species. Furthermore, the water vole is facing all the risks associated with geographically scattered and isolated subpopulations. It is suspected that the rate of population decline exceeds 30% over a 10-year period.

Geographic Range [top]

Range Description: The Southwestern Water Vole, Arvicola sapidus, occurs only in freshwater habitats in parts of France, Spain and Portugal, where it is found from sea level to a maximum of about 2,300 m in the Pyrenees (Le Louarn and Quéré, 2003).

In France, the water vole remains relatively common in only three regions: Charente-Maritime, Brittany and southwest France (Pyrenees), though its distribution is still patchy in these areas. In the French départements of Drôme, Var, Alpes-Maritimes, Hautes-Alpes, Alpes-de-Haute-Provence, Loire, Rhône and Ain, the water vole has become rare, with a maximum of only 10 locations per département. In the Ain there is only one location, two in the Rhône and no more than 6 or 7 in the Hautes-Alpes.

In Spain, the 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.

Locations of the water vole in Portugal are not well-documented but, as in other parts of its range, the water vole seems to be restricted to fairly isolated subpopulations in only a few parts of the country.
Countries:
Native:
France; Portugal; Spain
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The water vole is declining in most parts of its range. In France it is much less common than it was 10-15 years ago (S. Aulagnier, 2006), and in the Iberian Peninsula it is considered to be declining as a result of habitat loss and degradation (Palomo and Gisbert, 2002), although it is not currently classified as threatened in Portugal (Cabral, 2005). Several studies have shown that, in optimal habitat, water vole density can reach five individuals per 100 m of river bank, but that it is unlikely to exceed this figure (Saucy 1999, Palomo and Gisbert, 2002). Population fluctuations are not known (Saucy 1999).

France
A recurring problem with accurately determining the full extent of water vole population decline is that the species has been poorly documented in the past, with older information on water vole population being anecdotal and patchy. For example, an atlas of mammals of France (1984, Société Française de l'Etude et Protection des Mammifères - SFEPM) mentioned no threat to the water vole, and reported a nation-wide distribution of the species, with the exception of Corsica, the North, North-East and the Alps. There were no national surveys on the water vole and the vole was not even mentioned in the Action Programme for wild fauna and flora, a wide-ranging survey published in 1996 by the French Ministry for the Environment. In contrast, over the last 10 years there has been increasing attention on the water vole, mainly owing to its apparent disappearance from many areas, a great cause for concern in a species with a normally high reproductive potential (3 to 4 litters per year, averaging 3.5 young per litter). These recent observations and studies all point to its rapid decline.

Spain
The water vole has previously been little known and studied in Spain, yet it is probable that its numbers have suffered drastic declines in recent years, making it crucial to carry out further research and monitoring of the species (J. Román pers. comm., 2007). Experts in Spain seem to agree that the water vole is facing similar threats in the Iberian Peninsula as those in France (M. Delibes pers. comm., 2007). The water vole is not currently classified as a threatened species in any part of its range in the Iberian Peninsula, yet its subpopulations in this region exhibit a marked reduction, due to human-induced habitat degradation, destruction or modification, such as cementing over of riverbanks, canal-building, destruction of vegetation along waterways, draining of wetlands and water pollution (Álvarez, 1985; Garde, 1992).

Portugal
The water vole faces a situation similar in Portugal to that confronting its subpopulations in France and Spain, though its status in this country is perhaps the least well-documented of the three. Research conducted in several locations in Portugal where the water vole is present leads to the conclusion that it is scarce and under threat principally from habitat disturbance and predation, as well as isolation of subpopulations owing to the scattered nature of suitable habitat in Portugal.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: The water vole is almost always found near to water, preferring small (under 8 ha) freshwater lakes, ponds and slow-moving rivers and streams with dense riparian vegetation (Saucy 1999, Fedriani 2002). It sometimes occurs in drainage ditches and wet fields. Abundant hydrophilic vegetation and shorelines suitable for water vole burrowing activity seem to be essential characteristics of water vole habitat. Its diet consists mainly of aquatic plants, grasses, and herbs, although small animal prey are occasionally taken (insects, fish, tadpoles, freshwater shrimp). The burrows of the water vole typically have two entrances - one primary entrance above water level and one underwater entrance. The water vole is mainly active during the day, with two peaks in activity in late morning and early afternoon, as well some nocturnal activity. It is active throughout the year, with no period of hibernation.

Reproduction occurs between March and October, with 3 to 4 litters of 2 to 8 young per litter, with the average reported as 3.5 to 6 young. The gestation period is 3 weeks. Sexual maturity is reached at 5 weeks old and the life span of the water vole varies from 2 to 4 years. The water vole lives in small family groups and, under optimal conditions, its density may reach 5 individuals for every 100 meters of riverbank (Saucy 1999, Palomo and Gisbert, 2002). There have never been any records of damage to human activity or agriculture by the water vole.
Systems: Terrestrial; Freshwater

Use and Trade [top]

Use and Trade: In some parts of its range (Spain) the water vole is considered a delicacy and is still consumed occasionally.

Threats [top]

Major Threat(s): Since the water vole is restricted to wetland areas, it faces all the usual threats associated with this habitat. The water vole only flourishes where the banks and vegetation have not been significantly altered by human activity. Consequently, habitat loss and degradation (as a result of drainage, dredging, canal-building, infrastructure development, intensive agriculture, and so on) are major threats. Competition with the introduced Coypu and Muskrat for food and dens is also a threat. In Spain, water vole decline is attributed primarily to anthropogenic habitat modification, but competition from the Norway rat may be an additional factor threatening the water vole (Palomo and Gisbert 2002). Efforts to control invasive species by poisoning have resulted in accidental water vole deaths.

In descending order of importance, the principal threats are:
Secondary poisoning with anticoagulant rodenticides (Bromadiolone and Chlorophacinone) intended for the Norway Rat, Coypu and Muskrat,
Competition for habitat and food sources with the Muskrat and Coypu,
Predation by the American Mink, Polecat and Norway Rat, as well as domestic dogs and cats,
Trapping and shooting of "vermin",
Habitat modification, including draining of suitable wetlands, dredging, canal-building, disturbance by human activity and livestock, etc.,
Drastic variations in water level caused by dams or seasonal droughts,
Pollution and possibly disease and parasites.

Conservation Actions [top]

Conservation Actions: The water vole occurs in some protected areas within its range, although this does not particularly improve the status of this species (European Mammal Assessment Workshop 2006). As yet, the water vole receives no legal protection under EU legislation (Cabral et al. 2005), nor under national legislation in any of the three countries where it occurs. Further research and monitoring is urgently needed to supervise the population trend, and the aquatic habitats where the water vole occurs require protection.

Nature et Humanisme and the SFEPM recommend the following methods for protecting the water vole (J.F. Noblet pers. comm.):
-Prevention of the use of rodenticides in the habitats occupied by the water vole.
Alternative methods of combating the proliferation of the Muskrat, Coypu and American Mink, by more selective means (live cage traps, etc.).
-Forbidding the raising, import, transport or release of these three animals.
-Legislative protection of the water vole, under Annexes I or II of the EU Habitats Directive, the Bern Convention, as well as in national legislation,Legislative protection of the water vole?s habitat.
-Information campaigns directed at the concerned parties (local elected officials, waterway engineers, waterway management bodies, etc.).
-Regulation of management techniques of water ways and their shores, such as forbidding dredging and paving of water vole habitat and destruction of riverside vegetation.
-Forbidding destructive agricultural practices and associated water pollution.
-International cooperation between France, Spain and Portugal in protecting the water vole and coordinating research in cross-border areas where the water vole may occur.
-An ongoing research programme, in order to thoroughly map and monitor the remnant populations and their trends and to analyse the reasons for their ongoing decline.
-A captive breeding programme and eventual reintroduction of the water vole in suitable protected habitat.

Citation: Rigaux, P., Vaslin, M., Noblet, J.F., Amori, G. & Palomo, L.J. 2008. Arvicola sapidus. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 29 July 2014.
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