Name: House Mouse, Mus musculus.
Gestation: 19-20 days
Weaned: 21-23 days
Sexually Mature: 5-6 weeks
Grey brown fur which is only slightly lighter on the underside, with a tail which is 80% the length of the head and body combined. Adult M.musculus weighs on average 15-18 grams and has a combined head and body length of 70-90mm.
Show very little Neophobia (fear of new objects) response. In-fact many populations will actively search out and interact with new objects within their environment.
M.musculus will avoid wet or damp conditions, but is very tolerant of cold conditions.  Usually found to infest houses they are rarely found outside where they are readily outcompeted by other rodents, like the wood mouse.
Signs of Infestation 
• Sightings – The surest sign of any infestation.
• Smell – Rodents produce a distinctive odour in their urine. This can be particularly pronounced if the population is confined to an enclosed space or is very large. M.musculus will over time build urine pillars by many individuals constantly urinating in the same place.
• Droppings – Are on average 3-7mm long and described as being spindle shaped.
• Runs – Rodents reuse the same runs to such an extent that holes gnawed under doors and smears can be clearly seen leading away from burrows.
• Footprints and tail swipes – Mice move with their tails lifted up off the floor, this distinguishes their tracks from those of the rat.
• Damage – Perhaps one of the clearest signs of rodents is the damage they cause by their perpetual need to gnaw. M.musculus can be distinguished by the grooves caused by the incisors being roughly 1mm apart.
BPCA Manual, Chapter 6.