Fur brown on the back and white on the underside with a complete band of yellow fur across the neck area. Large ears, protruding eyes and long tail.
Head/body length 95-120mm; Tail 77-118mm
Found over a restricted range in Britain, the yellow-necked mouse may be locally common but nationally its status is unclear. It is thought to favour mature deciduous woodland but it is a regular visitor to houses in some areas. Its national range may be limited by climatic factors, possibly showing an aversion to wetter, colder areas. Its distribution is also associated with that of long established woodland sites.
Yellow-necked mice are largely nocturnal and are expert climbers. They make full use of the woodland floor and canopy when moving. Home range sizes are generally slightly larger than those of wood mice and home ranges overlap between and within the sexes. Generally their ranges are less than 0.5 hectares, shrinking in the non-breeding season and increasing for males in the spring.
Feeding primarily on tree seed, fruits, some green plants and invertebrates their diet is very similar to their close relative the wood mouse. They may specialise on eating tree seeds, possibly selecting those species of seed with the highest energy value. Food may be stored in their complicated underground burrow systems. Burrows are often constructed amongst root systems and contain nests furnished with plant material as bedding. The tunnel system can be extensive, covering a wide area and having several entrances. Nests may also be found above ground in tree holes, dormice boxes and in houses.
Yellow-necked mice have successive pregnancies from February to October producing litters of 2-11 young. Males become reproductively active first in the spring and the onset of breeding falls 2-8 weeks earlier than for wood mice where the two species occur together. The pups are born naked and blind weighing about 2.8g. Their eyes open after 13-16 days and their distinctive yellow collar of fur is discernible by then. Animals born in spring reach sexual maturity in 2-3 months while animals born later in the year develop more slowly and do not breed until the following year. In years of high tree seed abundance the breeding season may be prolonged into the winter. Few mice survive more than a year and the average life expectancy of juveniles is only 3-4 months. The population peaks in the autumn then declines over winter into spring before increasing again.
Yellow-necked mice are rarely seen except where they enter property. Traditionally some houses in rural settings experience a seasonal problem of invasion by this species They can be a pest, spoiling and consuming stored food or interfering with electrical wiring. They are unlikely to cause much damage to field crops due to their close affinity with woodland.
The unusual distribution of the yellow-necked mouse remains to be fully explained. The current status of this species is also less than clear, despite being common in some areas. In an endeavour to throw light on these matters The Mammal Society is launching a National Survey this year to include substantial live-trapping studies in the autumn 1998.
Yellow-necked mice have no legal protection. Priorities for their conservation will be established in the light of the National Survey findings.
What features best distinguish yellow-necked mice from wood mice?
Wood mice have a patch of yellow fur on the neck but never a complete collar like the yellow-necked mouse. Yellow-necked mice are also larger, more aggressive and often vocalise if handled.
Do yellow-necked mice and wood mice compete?
Yes - they compete for resources in shared habitat but the overall interaction is weak and neither species can exclude the other. Where actual encounters occur the larger yellow-necked mouse prevails.
Why do yellow-necked mice enter houses and what can be done to remove them?
Houses may offer warm accommodation to mice in the winter months and yellow-necked mice, being good climbers, seem to be especially keen on houses. Without killing mice the use of live-capture plastic traps, available from pet shops, is the best way to remove them. Release the mice at least 2 miles away.
Life cycle -- Males live separate from females. In winter male homeranges are slightly larger than those of females and reflect the higher food requirements of the heavier males. During the breeding season from February to October male homeranges increase to 2-3 times those of females as males search for non-pregnant females. Between 2-11 young are born in a litter. Most mice do not survive more than a year. They are mainly nocturnal.
Habitat -- Mature deciduous woodland, but will use mature hedgerows and scrubland. Live in a multi entrance burrow system, but are good climbers and forage in trees.
Diet -- Tree seeds, fruits, greenplants and invertebrates.