Rat Droppings

Identifying the animal from the droppings

Three animals account for almost every case in a Melbourne home, and the droppings separate them clearly once you know the measurements.

Roof rat (Rattus rattus, also called the black rat) droppings are 8 to 13 millimetres long, curved or spindle-shaped, and pointed at both ends. This is the species most often found in Melbourne roof voids, so scattered droppings through ceiling insulation, along the top of a wall plate or on stored items in the roof usually point here. See our roof rat guide.

Brown rat (Rattus norvegicus, the Norway or sewer rat) droppings are larger at 15 to 20 millimetres, noticeably thicker, capsule-shaped and blunt at the ends rather than tapered. Brown rats are ground-dwelling burrowers, so these turn up in subfloors, garages, sheds, along fence lines and near compost and bin areas. See our brown rat guide.

House mouse (Mus musculus) droppings are much smaller at 3 to 6 millimetres, roughly the size and shape of a grain of rice, and pointed at the ends. Mice produce far more of them — a single mouse can leave dozens in a night — so a scattering of very small droppings in a drawer, a pantry or a kitchen cupboard is mouse activity rather than a young rat. See our house mouse guide.

The species are recorded in the Atlas of Living Australia, which is a reliable reference for distribution across Victoria.

Droppings that are not rodents at all

A reasonable proportion of the droppings we are asked about turn out to belong to something else, and it changes the job completely.

Possum droppings are the most common confusion in Melbourne roof voids, because possums and roof rats occupy the same space. Possum droppings are considerably larger at 15 to 25 millimetres, more cylindrical with rounded or slightly tapered ends, and often show a visibly fibrous texture from a diet of leaves and fruit. They tend to accumulate in concentrated piles at a latrine site rather than scattering along runways. Possums are protected in Victoria and require a humane exclusion rather than treatment, so getting the identification right genuinely counts — see our possum removal service.

Cockroach droppings from larger species can be mistaken for mouse droppings but are much smaller, blunt-ended and ridged along their length, and are usually accompanied by a musty odour and dark smear marks in cupboard corners.

Bat droppings look superficially like rodent droppings but crumble readily to a glittery dust of insect fragments when disturbed, since bats eat insects. Bats are also protected wildlife.

If you are unsure, photograph the droppings next to something of known size — a coin or a ruler — before disturbing anything. That single photo answers most identification questions and saves a wasted treatment.

What the droppings tell you beyond the species

How recent the activity is. Fresh droppings are dark, soft and moist with a slight sheen, and they are usually less than a day or two old. Over several days they dry, harden and dull, and older droppings become grey, brittle and crumble when pressed with a stick. A useful test when you want to know whether a problem is current: clear an area completely, then check it again after two nights. Anything new means an active population, and it tells you which runways are in use.

How many animals there are. A rat produces roughly 30 to 50 droppings a day and a mouse considerably more. A handful of droppings in one location suggests limited activity or a single animal passing through. Heavy accumulations spread across several separate areas, particularly along walls and in more than one room or void, indicate an established population rather than a visitor.

Where they are living and travelling. Rodents move along edges rather than crossing open floor, so droppings mark the runways: along skirting boards, the top of wall plates, joists, the edges of stored boxes and the route between harbourage and a food source. Concentrations at one point suggest a nest nearby. That distribution is what we read on an inspection to decide where treatment and proofing go, which is why we prefer to see the droppings in place rather than have them cleaned away before we arrive.

The health risk, stated accurately

Rodent droppings and urine can carry organisms that cause human illness, and the risks worth knowing in Australia are different from the ones American guidance emphasises.

Leptospirosis is spread through the urine of infected animals, including rats, and can enter the body through broken skin or the eyes, nose and mouth, often via contaminated water or damp material. Better Health Channel covers it for Victoria.

Salmonella can be carried in rodent droppings and transferred to food or food-preparation surfaces, causing gastroenteritis. healthdirect covers the symptoms of food poisoning, and this is the practical reason droppings in a pantry or on a benchtop warrant discarding exposed food rather than wiping it off.

Allergens. Dried droppings, urine and shed hair break down into fine airborne particles that can trigger asthma and allergic reactions, particularly in children. This is the mechanism behind the cleanup rule in the next section, and it is covered by Better Health Channel’s guidance on asthma and allergens.

Hantavirus appears prominently in American cleanup advice. The strains that cause hantavirus pulmonary syndrome in the Americas are not established in Australia, so guidance written for a United States audience overstates that particular risk here. The precautions below are worth taking regardless, because leptospirosis, salmonella and the allergen risk are real and local.

How to clean up droppings safely

Do not sweep or vacuum them. This is the single most important point on the page. Both actions aerosolise dried droppings, urine and hair into fine particles that are then breathed in, which is precisely the exposure route worth avoiding. A domestic vacuum without a sealed HEPA system will also blow those particles back into the room through the exhaust.

The safe method is to wet everything first. Ventilate the area by opening it up for around half an hour before you start. Wear disposable gloves, and a P2 mask if the area is enclosed like a roof void or a subfloor. Spray the droppings and the surrounding surface thoroughly with a disinfectant or a bleach solution made up per the product directions, and leave it to soak for at least five minutes so nothing is disturbed dry.

Pick the material up with paper towel, place it into a plastic bag, seal it, then place that bag inside a second bag and put it in the outside bin. Disinfect the whole surrounding surface afterwards, including the areas the droppings did not sit on, because urine trails spread further than the droppings do. Remove gloves last and wash your hands thoroughly with soap and water.

Contaminated soft material — insulation batts with heavy soiling, stored fabric, cardboard — is generally better discarded than cleaned. For a heavily contaminated roof void or subfloor, this is work worth handing over rather than doing yourself, both for the exposure and because the space needs assessing for entry points at the same time.

One thing worth resisting: clearing every trace before an inspection. Where the droppings are is the map of how the animals are moving, so if you can leave the roof void or subfloor untouched until we have looked at it, the treatment and proofing end up better targeted.

What to do once you have identified them

Droppings confirm activity but do not fix it, and the two things that end a rodent problem are treating the population and closing the way in. Treating without proofing produces a property that is simply restocked from the surrounding area, which is the usual reason a household finds itself baiting every autumn.

Our rat and mouse control service starts with an inspection that identifies the species, locates harbourage and runways, and finds the entry points — gaps at the eaves and roofline, unsealed subfloor vents, service penetrations, gaps under doors and openings left where old plumbing was replaced. We treat the active population, then carry out the exclusion work so the access is closed.

Where droppings turn out to be possum rather than rodent, the work changes entirely to a humane possum exclusion, because possums are protected in Victoria and cannot be relocated away from the property. Getting that identification right at the start is the difference between a treatment that works and one that was never going to.

All products we use are registered with the Australian Pesticides and Veterinary Medicines Authority and applied by licensed technicians, and every treatment carries our pest-free guarantee.

Rat Droppings FAQs