144.

Cabrera’s Vole

Microtus cabrerae

French: Campagnol de Cabrera / German: Cabreramaus / Spanish: Topillo de Cabrera

Taxonomy. Microtus cabrerae Thomas, 1906, “Sierra de Guadarrama, near Rascafria, N. of Madrid, [Spain]. Altitude about 1000-1300 m.”

Microtus cabrerae is the only living member of the subgenus Ilberomys. It shows closer phylogenetic affiliations with Nearctic Microtus than its Palearctic congeners. It probably evolved from fossil M. brecciensis during late Middle Pleistocene. Monotypic.

Distribution. Endemic to Iberian Peninsula (Spain and Portugal).

Descriptive notes. Head-body 100-135 mm, tail 30-52 mm; weight 30-78 g. Cabrera’s Vole is stout, with tail ¢.34% of head—body length. Ears are moderately long and protrude from pelage; eyes are rather small. There are six plantar pads. Females have two pairs of inguinal and two pairs of pectoral nipples (eight nipples in total). Fur is soft and dense, buffy wood-brown interspersed with long black guard hairs that have buff or white tips or subterminal bands on back and flanks. Belly is yellowish cream-buff. Feet are brownish buffy, and tail is obscurely bicolored. Skull is strongly convex in dorsal profile, with deep and rounded braincase,slightly tapering nasals and conspicuous longitudinal furrow between supraorbital ridges. Incisors are clearly opisthodont. Molars show no peculiarities. Terminal loops on M? and M,are very short.

Habitat. Prefers natural pastures over thickets, pine plantations, cropland, and managed pastures from sea level to elevations up to ¢.1500 m (most often 500-1200 m). Cabrera’s Voles occur in regions with Mediterranean climates that receive 600-1200 mm of annual rainfall and have low-to-medium humidity (below 85%). Herbaceous vegetation, mostly above 30 cm tall, must remain green year-round; therefore, Cabrera’s Voles are, in most cases, restricted to proximities of small streams, ponds, and agricultural margins that are fed by high water tables or irrigation ditches. Soil is acidic to neutral (pH 3-7), with high moisture. Optimal habitats are typified by bentgrass ( Agrostis castellana and A. pourretii), slender oat ( Avena barbata), false brome ( Brachypodium phoenicoides), greater quaking grass ( Briza maxima), brome ( Bromus hordeaceus and B. madritensis), fescue ( Festuca ampla), fragile oat ( Gaudinia fragilis), velvetgrass ( Holcus lanatus), sunolgrass ( Phalaris coerulescens), common reed ( Phragmites australis), and annual fescue ( Vulpia myuros), all Poaceae;trailing StJohn’s-wort ( Hypericum humifusum, Hypericaceae); European umbrella milkwort (7olpis barbata) and hawkbit ( Leontodon), both Asteraceae; and cattail ( Typha, Typhaceae). Shrubs in such areas include blackberry ( Rubus, Rosaceae); rockrose ( Cistus, Cistaceae); gorse ( Ulex) and greenweed ( Genista), both Fabaceae; false yellowhead (Duttrichia viscosa, Asteraceae), and lavender ( Lavandula luisieri, Lamiaceae). Populations of Cabrera’s Voles are frequently fragmented, small, and widely isolated; therefore, landscape connectivity is important.

Food and Feeding. Cabrera’s Vole eats vegetation, only occasionally insects. Staple diet is leaves, stems, and seeds of monocotyledonous plants, in particular grasses ( Poaceae), sedges ( Cyperaceae), rushes ( Juncaceae), and lilies ( Liliaceae). It is selective, preferring some plants (e.g. brome) and avoiding others (e.g. false yellowhead). Clippings of vegetation are commonly found on runways.

Breeding. Reproductive activity of Cabrera’s Vole is not restricted to particular seasons, but it can be higher in winter and suppressed by summer droughts. Low rainfall combined with high temperatures inhibits reproductive activity. Breeding seasons last 23-24 days. Breeding nests are built 5-6 days before parturition. Numbers of embryos are 3-7/female (mean 4-9); litters are slightly smaller, with 3-5 young/litter (mean 4). At birth, young weigh 2:9-4-2 g (mean 3-5 g). They are deaf, blind, and hairless. Eyes open at eleven days old. Young start to explore surroundings at twelve days old and feed on solid food by 13 days old. They are weaned at 15 days old when they weigh 10-14 g.

Activity patterns. Daily activity of Cabrera’s Vole is mostly diurnal, with peak around noon in October-April and at dawn and dusk in May-September. Annual activity peaks in winter. Cabrera’s Voles are most active in sites with dense vegetation, and they move through it using surface runways. They move among habitats (e.g. spending dry summers in moist microhabitats). Although site fidelity is strong, residency time in a habitat patch usually does not exceed four months, except in large habitat fragments. At high ambient temperatures, Cabrera’s Voles become heterothermic.

Movements, Home range and Social organization. Dispersal abilities of Cabrera’s Voles are crucial to maintain metapopulations. On average, a colony occupies 1928 m?, and mean nearest neighbor distance is 363 m. Cabrera’s Vole can move 448 m/night and cross at least 1364 m in several months. Monthly home ranges are 40-1000 m? (mean c.300-400 m?), and core areas, where animals spend ¢.50% of their time, are 2-182 m®. Home ranges overlap widely (87%) between males and females and among females but not among males. Both sexes scent-mark with urine and feces for intersexual communication. Mating system is monogamous, with possible facultative polygyny. After parturition, males spend most of their time with females and young.

Status and Conservation. Classified as Near Threatened on The IUCN Red List. Cabrera’s Vole has a small area of occupancy (currently ¢.115,000 km?) and presumably declining populations. It was present in southern France until 1000-2000 years ago. In Spain and Portugal, it is classified as vulnerable. Main conservation problems relate to habitat loss and fragmentation. Due to habitat-patch dynamics in agricultural landscape, extinction and colonization rates are high, reaching values of 33% and 17%, respectively. Not surprisingly, agricultural disturbance is blamed for more than 50% of local extinctions.

Bibliography. Fernandez-Salvador (2002), Gomeset al. (2013), Laplana & Sevilla (2013), Mathias et al. (2003), Mira et al. (2008), Niethammer (1982c¢), Pita, Beja & Mira (2007), Pita, Mira & Beja (2006, 2014), Ventura et al. (1998).