About Arvicola sapidus Miller, 1908
The southwestern water vole, also called the southern water vole (Arvicola sapidus Miller, 1908), is a large amphibious vole native to most of France and the southwestward region spanning Spain and Portugal. It is classified as a Near Threatened species on the IUCN Red List. This vole occupies scattered, specialized habitats, most commonly small vegetation patches on muddy soil alongside water bodies. It uses dense vegetation cover for protection from predators and drought. In southern Spain, these suitable habitats make up less than 2% of the studied region, which leaves the species' populations naturally fragmented and vulnerable to local extinctions. Even though the southwestern water vole is a habitat specialist, it has relatively generalist dispersal patterns. It is able to cross terrain that appears inhospitable to colonize distant patches of suitable habitat. Genetic studies using microsatellite markers and mitochondrial DNA have shown that gene flow between populations remains fairly high, even between non-adjacent habitat patches. This indicates the species has adapted to patchy, unstable habitats through effective long-distance dispersal strategies. Population genetic analyses found moderate genetic diversity, with significant genetic structuring that is explained mostly by geographic distance between populations, rather than by specific landscape features. Field studies have recorded an average dispersal distance of approximately 700 metres (2,300 ft), with no significant difference in dispersal distance between males and females. These ecological and genetic results emphasize the vole's resilience and adaptability in naturally fragmented landscapes. This pattern differs from that of the closely related European water vole (Arvicola amphibius), whose dispersal behavior is typically more restricted by landscape features.
