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.

Quick Reference: Identifying Rodent Droppings

Mouse Droppings

• Size: Small, around 3–7 mm long
• Shape: Thin and cylindrical, similar to grains of rice
• Ends: Typically pointed at both ends
• Colour: Dark brown or black when fresh
• Freshness Clues: Fresh droppings are glossy and dark; older ones fade to grey or brown and become dry and crumbly

Rat Droppings

• Size: Larger, usually 12–20 mm long
• Shape: Chunky and sausage-shaped, often compared to olive stones
• Ends: Tapered or blunt, depending on the species
• Colour: Usually dark brown to black
• Freshness Clues: New droppings appear moist and shiny; they harden and dull as they age

Mouse Droppings in Business Settings

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

In commercial settings such as food storage units, office ceilings, plant rooms, or behind shelving in retail environments, staff often overlook these droppings during routine cleaning. When found near stock, packaging, or food preparation areas, they can quickly cause contamination and breach hygiene protocols.

It is also important to distinguish mouse droppings from those of bats. Although similar in appearance, bat droppings crumble easily when touched because of their high insect content. Misidentifying them can lead to 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 often appear dark in colour and have a shape similar to an olive stone. Unlike mice, rats tend to defecate in the same spot repeatedly, so their droppings usually form concentrated clusters.

In commercial buildings, you commonly find rat droppings in plant rooms, boiler houses, electrical risers, storerooms, and near external bin areas. Although rats produce fewer droppings per day than mice, they cause more damage. Rats often gnaw on cabling, insulation, and pipework, leading to structural problems.

Sometimes, people confuse rat droppings with those of grey squirrels. If you suspect squirrel activity in loft spaces or service voids, conduct a detailed site inspection to identify the species and locate 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.