Apodemus sylvaticus - The common wood mouse

Written by Lachlan Royle, BSc Ecology and Conservation student 

The University of East Anglia is of course widely renowned for its incredibly abundant array of flora and fauna, harbouring just shy of six thousand species. One of these said species is the common wood mouse. 

The wood mouse is one of a number of small mammal species that can be found on campus, but perhaps the most numerous. Alongside it reside pygmy shrews, bank voles, yellow necked mice and on more fleeting occasions both water vole and water shrew can be glimpsed. 

History and Habitat

Captured wood mouse frozen as a self defence mechanism 

The common wood mouse is the most abundant and widespread rodent in the British Isles and is even found on some of the smaller more isolated islands. Stretching beyond Britain the wood mouse can be found in the vast majority of continental Europe with only a few northern blips where the environment is simply a little too harsh. Beyond Europe they can also be found in parts of northern Africa and many parts of Asia stretching up towards the Himalayas. 

Part of what makes this small rodent such a successful species is their adaptability, whilst they favour grasslands and wooded areas; hence the name. They are able to survive in most environments bearing they are not too harsh or exposed. 

Another key element to their success is their ability to produce offspring, a female wood mouse will have up to six litters a year with each litter capable of 8 young. However as wood mice are a very vulnerable target to predation very few of these young will make it to the two month marker of sexual maturity, as such very few wood mice die of old age with most dying before reaching their first birthday. 

Methods of Surveying 

Longworth traps pictured at UEA site

To aid in research of wood mouse population characteristics it is therefore important to obtain individuals. One of the most efficient ways to do so is with small mammal traps.  Specifically on the UEA campus Longworth traps were used by our group. A simple but effective trigger mechanism is alerted when anything over five grams enters the rear chamber of the trap. Whilst being generally effective there are important steps that must be taken to ensure these traps do not endanger the mice themselves in any way. Firstly traps must be set up with an eye on the weather, overly cold or rainy conditions could lead to the death of the mice, by freezing or drowning.  Another very important step to take is to avoid leaving the traps out for too long, it is generally routine to set up the trap in the afternoon and then collect them the following morning, whilst some mice will be content in the traps with the food sources, others may find the ordeal stressful and therefore shouldn't be left for too long. 

The success of these traps can be incredibly dependant, to provide a brief example from our groups sample of sixty, nine wood mouse were caught. Following this the traps were reinstalled and upon collection the following morning not a single wood mouse was caught; instead two shrews and two voles. There has been research to suggest that the most effective way to increase yield of capture in the traps is to place as far away from man made structures as possible and to also place out on warmer evenings.