Harvest Mouse Micromys minutus

Harvest Mice are the smallest British rodents, being just 5 to 7 cm in length and weighing only 4 to 6 grams. They have a blunt nose and small hairy ears, in contrast with other British species of mice. Harvest Mice use a wide range of habitats and are excellent indicators of the health of their environment. They are found in linear features such as hedgerows, ditches, field-edges and roadside verges, but are now rarely found in cereal fields. Harvest Mice are often the most abundant small mammals in wetlands, where they occur in reed and sedge beds. The most obvious signs of the presence of Harvest Mice are the characteristic breeding nests woven of grass leaves well above ground level.

Harvest Mice are extremely active climbers and feed in the stalk zone of long grasses and reeds. They eat a mixture of seeds, berries and insects, although moss, roots and fungi may also be taken. Harvest Mice are caught and eaten by many predators including Cats, Weasels, Stoats, Foxes, Owls, Hawks and Crows.

Current Status

The Harvest Mouse was once described as 'common and widespread' throughout Britain, but the national distribution has become more limited in recent years. The current distribution and status of the species is not certain. The Harvest Mouse is mainly found from central Yorkshire southwards with isolated records from Scotland and Wales.

Old Main Drain, which runs from north to south along the eastern edge of North Bransholme, is a stronghold for the Harvest Mouse in Hull. Insensitive mowing has damaged the scrubby strip between Old Main Drain and the North Bransholme housing. The once varied vegetation has been reduced to inch-long grass. This will have affected Harvest Mice, although they are still present in the hedgerow along the drain itself and the adjoining arable fields. The drain hedgerow and arable area directly opposite Highlands School/Health Centre is especially good for Harvest Mice.

Current Factors Affecting Harvest Mice

• Modern agricultural techniques have negatively affected Harvest Mouse populations in a number of ways. Removal of hedgerows has resulted in loss of winter refuges and corridors that were previously used to colonise other sites. Changes from spring to winter sown crops means that harvests often occur earlier, before the peak of the Harvest Mouse breeding season. The shorter stemmed cereals now grown are also less suitable for nest building. Drainage of wetlands for agriculture has removed much of the favoured reed and sedge habitat. Harvest Mice eat insects therefore the increasing use of insecticides may have contributed to the decline in numbers. They are also sensitive to herbicide and fungicide poisoning.
  
  
• Many areas in Hull are becoming unsuitable habitats for Harvest Mice due to insensitive management such as frequent mowing of grass verges.
  
  
• Harvest Mice have a range of predators and this may be a factor in the loss of some populations.
  
  
• In urban areas, continued absence from suitable habitats may be due to the effects of habitat fragmentation and isolation.

Current Action

Legal Status

Harvest Mice are not legally protected in Britain.

Management, Research and Guidance

The Mammal Society has initiated two national surveys. One includes over 800 sites and simply looks for the nests. The second involves 25 groups in Britain using tennis balls as feeders. The Wildlife Trust is providing tennis balls, which can be used as artificial nests in areas of identified conservation need. The new homes have been regularly checked to see if Harvest Mice are using them, however the project has not been very successful so far.

There is currently no action for Harvest Mice in Hull.

Action Plan Aims

1. To determine the population and distribution of Harvest Mice in Hull.
   
2. To relax mowing regimes on grass verges, river/drain banks and amenity grassland.

What We Are Going to Do

What We Can All Do

Help the Biodiversity Partnership find out where Harvest Mice occur in Hull. Although you are unlikely to see a Harvest Mouse active in the wild, they may be brought in by your cat. The woven nests are also a sign of their presence.

Grass verges may be left uncut until late summer, so as not to disturb Harvest mice and other grassland species. Be aware that they are being specifically managed and have not been neglected.
 

Links With Other Action Plans

Management of Grassland, Trees, Scrub and Hedgerows and reedbeds associated with Fresh Water Habitats will be important to the conservation of the Harvest Mouse.

References

Corbet, G.B., Harris, S. (1991) The Handbook of British Mammals. (3rd edition) Blackwell, Oxford.

Harris, S. (1995) A Review of British Mammals: Population Estimates and Conservation Status of British Mammals other than Cetaceans. JNCC, Peterborough.

The Mammal Society. Mammal Fact Sheets: The Harvest Mouse. (Retrieved November 2001 from http://www.abdn.ac.uk/mammal/harvest.htm).

The Wildlife Trust. Northamptonshire Harvest Mouse Action Plan. (Retrieved December 2001 from http://www.northamptonshire.gov.uk/council/documents/bio).