Mice and Rats

Mice and rats sit under one heading but they are not the same animal. They differ in size, in the gaps they use, in where they nest and in the signs they leave. Knowing which one is in a building changes how the problem is handled. Both are there for the same reason: they can get in.

Mouse or rat

A house mouse is small. Total length including the tail is 13–18 cm, weight around 14 g, and the coat runs from light brown to grey. The tail is long in proportion to the body.

A brown rat is large and heavily built, an adult weighing anywhere from 200 to 500 g. Its tail is shorter than the head and body together — laid back, it reaches only to the middle of the skull. That proportion is the reliable test, because a young rat can pass for a big mouse on size alone.

Where they get in and where they nest

A house mouse can pass through a gap of 6 mm. For a rat, roughly 13 mm under a door is enough, and young rats in particular use it freely. That is why anything larger than 6 mm counts as an opening to be closed.

Mice nest indoors, in a void close to warmth and food. Rats prefer the outside: they burrow along building foundations and beneath rubbish and woodpiles, and work in and out from there.

The signs they leave

You usually see the evidence before the animal:

• Droppings, particularly near food preparation and storage areas
• Fresh gnaw marks — rat tooth marks are around 4 mm, noticeably larger than a mouse’s
• Tracks in dust and runways along the base of walls
• A musky odour in enclosed spaces
• Burrow holes around the outside of the building

What it means for health and property

Rodents both eat and contaminate food. Disease agents associated with house mice include leptospirosis, salmonella and lymphocytic choriomeningitis. Those reported for rats include typhus, leptospirosis, foodborne illness from salmonella, E. coli and campylobacter, and rat bite fever. Mouse urine is a significant source of indoor allergens, and the US Environmental Protection Agency notes that pests such as mice and cockroaches can trigger asthma symptoms and allergic reactions. Persistent respiratory or skin symptoms are a matter for your doctor.

Structural damage is often noticed sooner. Rats gnaw cables, timber, plastic and even soft metals such as copper. A gnawed electrical cable is a genuine risk, usually behind a consumer unit or a machine where nobody is looking.

How their behaviour sets the layout

A house mouse seldom ventures more than nine metres from its nest. That governs where stations and traps go: spaced too widely, a line is simply never crossed. Rats range further and burrow outdoors, so the external perimeter goes into the layout too.

Breeding rate is what makes delay expensive. A female house mouse may produce five to ten litters a year of five or six young each, and those young breed at five or six weeks old. A brown rat produces four to six litters a year and can wean more than twenty young in that time. Every product we use is a biocidal product licensed by the Turkish Ministry of Health.

What you can do

The proofing material decides the outcome. Steel wool, sheet metal and mortar hold; plastic and timber are gnawed straight through and are not even a temporary fix. Fix leaks, keep food in lidded containers and do not leave rubbish standing. Clear woodpiles and builders’ rubble from around the building — for a rat that is a ready-made nest site.

Do not put poison bait down in the open. It puts children and pets at risk, and a rodent that dies in an unreachable void becomes an odour problem of its own.