Priority Species: Harvest Mouse
1. Determine the population and distribution of harvest mice in the Durham BAP area.
2. Protect, maintain and enhance habitat features required by harvest mouse
3. Create and manage large habitat patches suitable for re-introduction of, and colonisation by harvest mouse.
4. Ensure that land managers are aware of the habitat requirements of harvest mice and that known sites are managed appropriately
5. Increase public awareness and participation in harvest mouse conservation
The harvest mouse was once described as common and widespread throughout Britain occupying a wide range of habitats but favouring areas of tall, dense vegetation. It has always been more prevalent in southern counties. There is little known about the natural history, present status and distribution of the harvest mouse in the UK.
The species can easily pass undetected and is, therefore, vulnerable to under-recording.
Harvest mice have high energy requirements and are thought to eat a mixture of seeds, berries and insects although moss, roots and fungi may also be taken.
Breeding nests are the most obvious sign indicating the presence of harvest mice. The harvest mouse is the only British mouse to build nests of woven grass well above ground. They are generally located on the stalk zone of grasses; at least 30cm above ground in short grasses and up to a metre in tall reeds. The nest can vary from 10cm in diameter for breeding nests to only 5cm for non-breeding nests and tend to be found in dense vegetation such as grasses, rushes, cereals, grassy hedgerows, ditches and brambles. Nests tend to stand out more in winter when the surrounding vegetation dies back.
Harvest mice usually have two or three litters a year in the wild between late May and October or even December if the weather is mild although most litters are born in August. Cold wet weather is a major cause of mortality. There are usually around six young in a litter which are born in the carefully woven grass nests. The young are born blind and hairless but grow extremely quickly and start to explore outside the nest by the 11th day. The young are abandoned after about 16 days and continue using the nest which may at this stage start to look rather dilapidated. A fresh nest is built for each litter.
During the 19th century the harvest mouse was recorded from most of the counties of England and extended into south west Scotland. However Corbett & Harris (1991) state that though the range extends into Northumberland, most records are from central Yorkshire southwards. Recent Durham records are scarce and only 9 since 1960 in present county boundaries and a further 5 within Cleveland north of the river Tees. Some of these records are doubtful.
Recently two attempts at reintroduction have been made in Northumberland and four in Cleveland. The Cleveland records may be as a result of these reintroductions.
- Intensive farming methods – lack of unmanaged field margins, loss of hedgerows, crop rotation and use of pesticides reduces food availability and availability of reliable nest sites.
- Habitat destruction – fragmentation, wetland draining
- Lack of information and poor species identification – under-recording, and lack of knowledge of harvest mouse ecology
- Extreme weather conditions – linked-in with a naturally occurring `boom & bust` ecology, the added problems of habitat destruction etc listed above focus this issue.