86.

South-western Water Vole

Arvicola sapidus

French: Campagnol amphibie / German: Sidwesteuropaische Schermaus / Spanish: Rata de agua suroccidental

Other common names: Southern Water Vole

Taxonomy. Arvicola sapidus G. S. Miller, 1908, “Santo Domingo de Silos, Province of Burgos, Spain.”

Arvicola sapidus is sister to the other species of Arvicola . The most recent common ancestor to these species occurred 241,000-252,000 years ago. Two subspecies recognized.

Subspecies and Distribution.

A.s.sapidusG.S.Miller,1908—SSpainandPortugal.

A. s. tenebricus G. S. Miller, 1908 — France and N Spain.

Descriptive notes. Head-body 165-220 mm, tail 107-135 mm; weight 100-275 g. Males are on average larger, with a mean weight of 201-2 g compared to 172-8 g for females. The South-western Water Vole is similar in external appearance to the aquatic Eurasian Water Vole ( A. amphibius). Tail is c¢.66% of head-body length. Dorsal fur is yellowish brown to dull grayish buff, and belly is light ocherous buff, clouded by slaty gray hair bases. Tail is brownish and bicolored, and feet are drab gray. Anterior parts of nasal bones are heavily expanded.

Habitat. Strictly aquatic in still or slow waters with densely vegetated banks from sea level to elevations of 2300 m. The South-western Water Vole occurs in ditches, lakes, ponds, streams, rivers, marshy areas, and even brackish water.

Food and Feeding. Diet consists of aquatic plants, grasses, and various herbs. Most important are monocotyledonous plants: grasses ( Poaceae; relative frequency 51:6%), cattails ( Typhaceae; 17-5%), and sedges ( Cyperaceae; 16-:8%). Plants are gathered under the water. Animals (e.g. insects, crabs, fish, and amphibians) are rarely preyed on.

Breeding. Breeding season of the South-western Water Vole is in February—October but can extend throughout winter. Numbers of embryos are 1-8/female.

Activity patterns. South-western Water Voles are active day and night, with two peaks during summer in late morning and afternoon.

Movements, Home range and Social organization. South-western Water Voles are good at swimming and diving. They dig burrows in riverbanks.

Status and Conservation. Classified as Vulnerable on The IUCN Red List. Overall population of the South-western Water Vole has declined by 30% over a ten-year period, and decline is continuing because of ongoing habitat degradation.

Bibliography. Centeno-Cuadros et al. (2009a, 2009b), Garde & Escala (2000), Reichstein (1982a), Shenbrot & Krasnov (2005), Ventura (2002b).