158.

Mediterranean Pine Vole

Microtus duodecimcostatus

French: Campagnol provencal / German: MittelmeerKleinwiihimaus / Spanish: Topillo mediterraneo

Taxonomy. Arvicola duodecimcostatus de Sélys-Longchamps, 1839, Montpellier, Hérault, Southern France.

Microtus duodecimcostatus is in subgenus Terricola and duodecimcostatus species group. It is sister species to M. lusitanicus . Although these two species differ morphologically and occupy distinct ecological niches, they still do not achieve fully reproductive isolation. Molecular studies retrieved historical introgression of mtDNA from M. duodecimcostatus into M. lusitanicus and also identified recent hybrids. Distributions of the two species segregate with some overlap in central and northern Spain and Portugal. It was classified in the genus Pitymys . Up to seven subspecies have been recognized based on differencesin size, color, and degree of proodonty. It is now agreed that these traits vary clinally. Intraspecific genetic diversity seems to be low because M. duodecimcostatus is composed of a single unstructured group of populations sharing a P53 protein with a single mutation. Monotypic.

Distribution. S & SE France and Iberian Peninsula.

Descriptive notes. Head-body 80-111 mm, tail 19-35 mm; weight 19-32 g. Head of the Mediterranean Pine Vole is massive with blunt nose, small eyes, and short ears. Neck is powerful, body is chunky, and tail is short. Females have two pairs of inguinal nipples (four nipples in total). Furis long and soft, brown on dorsal side, shaded buff or gray, depending on location; belly is light gray. Skull is massive and deep, with expanded zygomatic arches. Alveolar process of mandible is prominent. Upper incisors are decidedly proodont. M, is long, but M?is short, with only three salient angles on innerside.

Habitat. Open grassy areas and arable land influenced by Mediterranean climate from sea levelto elevations of ¢.3000 m. The Mediterranean Pine Vole requires soils of intermediate thickness, on moderately inclined slopes but not rocky, with dense plant cover and shaded by tree canopy but without shrubs.

Food and Feeding. The Mediterranean Pine Vole feeds mainly on underground plant parts (bulbs, tubers, and roots), particularly of buttercup oxalis ( Oxalis pes-caprae, Oxalidaceae) and autumn crocus ( Colchicum montanum, Colchicaceae). Green plant parts and fruits are consumed to a much lesser extent. Barking of saplings have been reported. The Mediterranean Pine Vole locally attain high densities (up to 900 ind/ha) and can cause damage to agriculture, particularly in citrus fruit plantations.

Breeding. Breeding occurs throughout the year in northern Spain and France. Reproductive activity peaks in November-May and is the highest in February-March. In southern Spain, breeding is restricted to winter to avoid constraints of summer droughts. Gestation is 24 days. Females carry 1-5 embryos; mean numbers are lower in southern Iberian Peninsula (2) than in the north (2-5-3). Young are born naked and blind. Their initial weights of 2-2-8 g increase to 4-9-6-5 g by day 7, and they are sexually mature at 60-70 days old. Longevity of Mediterranean Pine Voles is up to 33 months for males and up to 27 months for females. In the wild, they normally survive two winters.

Activity patterns. The Mediterranean Pine Vole is fossorial and spends the majority of time in a burrow system. Digging is done with incisors and forefeet, and excavated soil is pushed by head to the ground’s surface and deposited in easily recognizable heaps. Soil is excavated at 10-8 g/minute by females and 7-5 g/minute by males. Daily amount of excavated soil under experimental conditions is 2092 g (2-4 dm’) per individual. Tunnels are normally 10-50 cm deep but can descend 1 m to reach humid soil in summer. As a rule, entrances to underground tunnels are sealed by mounds of excavated soil. Although the Mediterranean Pine Vole is predominantly subterranean, it is also capable of climbing and is a proficient swimmer.

Movements, Home range and Social organization. The Mediterranean Pine Vole lives in small colonies that average 3-1 individuals. Home range of a family group averages 50 m*. Matting system is monogamous, and rate of inbreeding is high.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Overall distribution is ¢.532,000 km?. At high densities Mediterranean Pine Voles may be agricultural pests and be controlled by chemical poisoning.

Bibliography. Bastos-Silveira et al. (2012), Cotilla & Palomo (2002), Giannoni, Borghi & Laconi (1999), Giannoni, Borghi & Martinez (1991), Niethammer (1982f), Quina et al. (2015), Santos, Mathias & Mira (2010, 2011).