Range & Status
Europe including Scandinavia, extends further north than the Wood Mouse Apodemus sylvaticus but more restricted in the south-west and absent from the Mediterranean basin. It is mainly montane in southern Europe (Corbet & Harris, 1996; Harris & Yalden, 2008). Native and locally common in Britain: mainly found in eastern and southern England, the English/Welsh Borders and southern Wales. Is absent from Scotland and Ireland (Harris & Yalden, 2008).
Only eight ' records' for Cornwall over a 28 year period, but possibly under-recorded, perhaps due to its similarity to the Wood Mouse (their skulls are particularly difficult to separate which may have led to them being missed in Owl pellet studies). Possibly a rare visitor to Cornwall, as it might be capable of considerable long distance movements over open ground (Morris, 1993); the occasional animal might have hitched a ride on imported timber, garden materials or similar goods. Yellow-necked Mouse has been recorded at Crantock, near the River Gannel, (SW76 and SW86) and at Rosenithon (SW72) in the mid-1970s, and more recently in east Cornwall in the Seaton Valley (SX35) and at Wheal Martin (SX05). Two more recent, single, records were received by ERCCIS for the years 2001 and 2003. However, it is possible that all these records are derived from wrongly identified individuals which were actually Wood Mice (although some might have been vagrants). The authors of the Yellow-necked Mouse section of Harris and Yalden (2008) list Cornwall along with Devon, Lincolnshire and elsewhere as ' appearing suspicious' in reference to their A. flavicollis records.
Habitat & Ecology
Yellow-necked Mouse mainly occurs in mature deciduous woodland (Corbet & Harris, 1996), particularly in ancient semi-natural woodland (Morris, 1993) and areas with higher summer temperatures (possibly linked to better tree seed production) (Harris & Yalden, 2008). Less favoured habitats include hedges, rural gardens and buildings. Other marginal habitats are found in coniferous woodland, occasionally reedbeds, wet woodland and heathland (Harris & Yalden, 2008). When found in woodland Yellow-necked Mouse prefers areas with limited ground cover but with dense cover one to five metres high (Corbet & Harris, 1996), and in coppiced woodland, it prefers older stands, avoiding recently coppiced areas. Structurally complex areas incorporating fallen deadwood may provide good areas for nests (Harris & Yalden, 2008). The diet includes seeds, green plants, fruits, and invertebrates. It readily takes to nest boxes erected for birds and Hazel Dormouse (Morris, 1993).
The loss and fragmentation of semi-natural woodlands is thought to be the main threat to this species (Morris, 1993). In Cornwall in 1986, 3122 hectares of such habitat remained, representing 45.1% of the amount of semi-natural woodland present in Cornwall in 1930 (CWT data). Yellow-necked Mouse numbers can be significantly affected by relatively small changes in habitat management (Harris et al., 1995).
There is a need to determine the true status and distribution of this species in Cornwall: verification of records is vital. Future sightings need to be properly recorded through detailed descriptions and photographic evidence of the yellow collar. The collar should be broad and in contact with the dark dorsal colour. This is consistently complete in this species and is even discernable in juveniles as a grey band (Harris & Yalden, 2008). Not included in the Biodiversity Action Plan list for Cornwall.