Hickory dickory dock, we have a mouse in the house

The House Mouse (Mus domesticus) is probably one of the most intelligent and fascinating creatures on earth. Mice are highly adaptable. They can gain access to a house via a gap that 5mm wide! They are quick to exploit cavities in the walls, roof spaces and ducts in buildings. They are excellent climbers and their harbourages may be situated at any level.



Brown grey in colour with a light underside, they have large ears, small eyes and weight approximately 10-25g. Sexually mature at 5-6 weeks, having 5-8 litters per year with an average litter size of 6 young. Average life span is only 3-4 months. House mice produce a few millilitres of wee per day as part of territory marking and can contaminate the objects or surfaces where it is deposited. Small “urine pillars” are indicative of long established infestation.Stale odours can be readily recognisable particularly when long established and occupy undisturbed indoor areas.


Mainly nocturnal, sleeping however makes up 30% of any 24-hour cycle and grooming up to 20% of their time. Grooming is a cleaning activity that involves licking their fur and feet. Mice are very susceptible to colder temperatures but highly adaptabledeveloping longer hair, smaller feet, ears and tails. They tend to spend more time with their litters and co-operate with each other by ‘huddling’ together when temperatures are low. They can survive in cold stores where they will conserve body heat by living in the most well insulated parts of the stores either in the walls or carcasses.


House mice are surprisingly indiscriminate in their choice of food preferring small grains such as canary seed, which they de-husk before eating and foods moistened with vegetable oils are generally well received. House mice have been termed “behaviourally resistant” because their avoidance of cereals is genetically based. Mice prefer foods, containing animal fats and even proteins and the use of similar specialist baits may be necessary to achieve effective control.


House mice are light, intermittent and erratic feeders tending to eat small amounts of food from many different sites. This has implications for their control thus requiring a correspondingly larger number of bait points by comparison to rat control. They can exist on very little water, providing their food source contains about 15% moisture. They will drink water if available from a free source. When feeding whole wheat to mice, they will hold the grain in their fore-paws and de-husk it with their teeth. The middle of the grain may be eaten as it is turned in the paws. Because of their intricate ecology it is best to call upon the services of a professional pest controller to deal with a mouse infestation.


House mice avoid wet damp conditions and prefer dry environments mainly because of their small size. After man they are the most numerous mammal on earth, well adapted at living with humans and exploiting the environments that humans create. While rodents are colour blind they compensate with their acute hearing and amazing ability to learn new surroundings by the constant practice of muscular movement (muscle memory – ‘kinesthesis’). They only burrow inside in warm, dry climates when the need arises. They exhibit a rapid investigatory response to new objects or food sources for a short time, but move on quickly to investigate something else. They are sporadic feeders with a limited neophobic response to new objects.


Transmission of disease from rodents to humans has had a major impact on human history e.g. plague, leptospirosis and many other diseases continue to impact today with rising urban populations likely to become more significant in the future. They carry many ectoparasites such as fleas and ticks.



Mervyn WalshBA(Hons), HDip.EnvMgt, MRSPH

Field Conservation Biologist