Signs of a Rodent Infestation

Signs of a Rodent Infestation

Evidence of the presence of rats, mice or squirrels can be established without the sighting of a live animal.

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Typical signs that can be seen both inside and out are; damage to building materials, packaging and food.

The teeth marks can give clues to the type of rodent; mice tend to nibble from the centre of a grain, rats often leave half grains or small pieces of debris.

Indications of how recent the activity is can be gained from the freshness of the gnawing on items such as wood;  if freshly gnawed the surface will have a light appearance in comparison to a few days later when it will have a darker appearance.

The presence of small chiselled pieces or cuttings in the vicinity will give clues of how recent the activity has been, they will soon be scattered if they have been there for any length of time.

Holes made by rodents in the ground, floors, walls, door bottoms will be sized according to the rodent, burrow entrances for a rat are approximately 8cm in diameter (2 1/2″) and for a mouse 2cm in diameter (less than an inch).

Black rats and mice generally conceal their nests, whereas entrances to Brown rat nests/burrows are easily recognisable and usually not difficult to find because they prefer to live and nest in the ground.

House mice that live in and around buildings rarely use burrows but do build nests in places such as cavity walls, in attics, between floors etc.
The age of rat and mouse burrows can to a certain extent be determined by how well worn they are. Holes in current use will be free of dust and cobwebs and may have a slick, beaten down appearance. Footprints may also be evident in dusty environments.

Rodents are creatures of habit and will regularly use the same run. The runs exhibit ‘smear’ marks as the grease, dirt and natural oils from their fur makes contact with the surfaces.
Outdoors these runways appear as clean-swept paths where vegetation has become flattened, about 5-7cm wide. They occur along the outside walls of buildings, in the embankments and under heavy growths of bushes.

Droppings also aid in the identification of an infestation; the Brown rat’s droppings are the largest and vary in shape from bluntly rounded ends to spindle shaped in appearance.
Black rat droppings are generally smaller and more regular in form with a banana like curve, the ends are usually pointed.
Mouse droppings are very small and are sometimes confused with cockroach droppings, so be alert to the differences between the two when conducting an inspection.
Cockroach droppings are much smaller than mouse droppings and are characterised by blunt, almost squared off ends and ridges.
When droppings are discovered it is important to determine their age as it will indicate whether the infestation is current.
Fresh droppings are soft enough to be pressed out of shape and have a glistening moist appearance.

The colour varies according to the kind of  food eaten, but usually they are black or nearly black. Within a few days, depending on climatic conditions, droppings become dry and hard. Later the surface will become dull, and over an extended period of time they assume a greyish, dusty appearance and may crumble easily.

The most positive proof of any infestation, is to see live rats or mice.

However, because rodents are generally nocturnal and secretive in their habits, live animals are seldom seen.

Rodents also make various noises which may highlight their presence and location, but  unless the area is very quite the noises are rarely heard.

Urine stains, hairs or the characteristic odour of rats and mice will be encountered in the case of an infestation.

On some surfaces stains show up clearly in normal light, on other surfaces they are revealed by the use of a black light. In heavy infestations a peculiar musty musk/urine odour may be present.


Vale Pest Control are located on the outskirts of Cardiff, ideally situated to cover Cardiff, Newport, The Vale, Bridgend and the Valleys.

Specialising in pest control and wildlife management VPC offer solutions to bird problems, rodent infestation, bedbug and flea infestation treatments.

For FAST, Friendly Service, Call  02920 552243

Speak to a local professional pest controller – not a national call centre!!!

Solve your rodent problem quickly and cleanly