How to Tell the Difference Between Rat and Mouse Droppings

Why Rodent Droppings Are a Key Indicator of Commercial Infestations

Rodent activity in commercial premises poses a serious risk to health, safety and regulatory compliance. One of the most common and visible indicators of an infestation is the presence of droppings. Correctly identifying whether these come from rats or mice is critical for deploying the right pest control solution and for reducing the risk of operational disruption or reputational damage.

Mouse Droppings in Business Settings

Mouse droppings are small, typically measuring between 3 and 7 millimetres, and are usually black or dark brown in colour. They resemble grains of rice and are often scattered across a wide area due to the high activity levels of mice. A single mouse can produce up to 80 droppings per day, making early detection essential.

In commercial settings such as food storage units, office ceilings, plant rooms or behind shelving in retail environments, these droppings are often overlooked during regular cleaning. Their presence near stock, packaging, or food preparation areas can quickly lead to contamination and breaches of hygiene protocols.

It is also important to distinguish mouse droppings from those of bats. Bat droppings, while similar in appearance, crumble easily when touched due to their high insect content. Misidentification can result in legal consequences, as bats are protected under the Wildlife and Countryside Act 1981. Always consult a professional pest control provider to ensure accurate identification.

Rat Droppings in Commercial Environments

Rat droppings are much larger than mouse droppings, generally measuring between 12 and 20 millimetres. They are often dark in colour and shaped like an olive stone. Unlike mice, rats tend to defecate in the same place consistently, meaning their droppings are usually found in concentrated clusters.

Common sites for rat droppings in commercial buildings include plant rooms, boiler houses, electrical risers, storerooms, and near external bin areas. Although rats produce fewer droppings per day than mice, they are more destructive. Their presence is often linked with structural damage, including gnawed cabling, insulation and pipework.

In some cases, rat droppings may be confused with those of grey squirrels. If you suspect squirrel activity in loft spaces or service voids, a more detailed site inspection is required to confirm the species and identify access points or nesting materials.

Why Accurate Identification Matters for Your Business

Recognising whether you are dealing with rats or mice is essential for selecting the correct pest control measures. This includes choosing the right bait, trap sizes and monitoring techniques, as well as ensuring treatment complies with industry-specific regulations such as HACCP, BRC and SALSA standards.

Failing to correctly identify the pest species can lead to under-treatment or inappropriate control strategies, increasing the risk of repeat infestations. This can result in contamination, product loss, reputational harm or even legal penalties if the issue is not managed in line with compliance requirements.

Speak to the Experts

If you have identified droppings or suspect rodent activity in your commercial premises, contact the OCS pest control team. Our trained professionals provide fast, discreet and compliant solutions tailored to your sector, helping protect your people, property and brand.