Outdoor cousins of the House Mouse, which tend to move indoors in the winter seeking their creature comforts.
It's important to understand that pest management professionals will avoid controlling field mice unless they are presenting a public health risk.
Field mice are small mammals of the order Rodentia.
Although mice are often considered to be cute by some people, they are a public health pest and can cause serious harm.
Mice have been known to spread nasty diseases - such as Salmonella and Listeria - to humans through their urine, droppings and bedding.
Mice have a need to mark their territory with their urine and due to their sporadic eating habits, build nests near food sources. This puts anyone with an infestation at risk of food poisoning.
As they scurry around, they carry dirt and bacteria with them, transferring it to your counter tops, cabinets, pantry and anywhere else they travel.
These nibbling nuisances can also cause a lot of property damage, due to their compulsive need to gnaw to maintain their teeth at a constant length.
Electric cables, water and gas pipes, packaging and woodwork may all be seriously damaged by mice - many instances of electrical fires and floods have been attributed to them.
As the weather gets colder, those field mice currently surviving outdoors will look for warmer places to nest and begin to move indoors.
They are highly adaptable and won’t hesitate to take advantage of a cosy human structure during the winter months.
Food is also an issue - they begin to scavenge closer to humans, as their own sources are no longer plentiful.
A field mouse has sandy brown fur with a lighter underside.
As it mainly lives outdoors, it has bigger eyes and ears than a house mouse. This is an adaptation to avoid predation.
Field mice also have long tails, making them quite agile climbers.
Juveniles are greyer overall, still with larger ears, hind feet and tails than house mice.
In comparison, the house mouse has a typical mouse profile: small feet with smaller eyes and thinly-haired ears, and a pointed snout with thin whiskers.
Their body length ranges between 60-90mm, and the tail generally equals the length of its body, adding another 90mm.
They weigh less than 25g, and their fur colour is uniformly light brown and grey, right down to the tail which has sparse hairs on it.
And keep those pegs handy - they have a really distinctive, strong smell so you’ll know if you have a large infestation of these unwanted guests.
Prevention is better than cure, so let’s take a look at how we can accomplish that.
Field mice only need a gap of 5mm to gain entry (roughly the diameter of the eraser end of a pencil).
You will need to search for any potential entry points and seal these up with wire wool embedded in quick-setting cement.
You should focus on low level gaps first as these are the most likely areas for field mice to enter. You can then consider any higher up vents or gaps.
Check around pipes and windows, and double check the basement.
Proofing all means of entry as much as possible will help to prevent an infestation.
Other steps you should take are:
Good hygiene practices won’t eliminate a mouse problem, but poor practices will attract them.
For any mouse infestation, we would always recommend contacting a professional pest control company.
They are trained in mouse control and professionals are able to take control of situations efficiently.
Field mice can be controlled by using non-chemical means with tools such as good root cause analysis, hygiene and housekeeping, proofing and then maybe a trapping programme.
There is only one rodenticide currently available for use on field mice.
A pest professional will take an integrated pest management (IPM) approach to tackle your infestation. They will always select the safest, most effective and legal product to use to control an infestation of field mice.
They will have access to monitoring equipment, which they will use to confirm entry points into your property and the infestation's size and to track the mouse to its harbourage (nest).
They can then recommend a proofing strategy and decide on the best course of action in terms of control.