Rodent detection dogs: how they find rats and mice

The hardest part of many rodent jobs is not the treatment. It is working out exactly where the rats or mice are living and how they are getting in. Trained detection dogs are one way of doing that. They are used in some settings to locate rodents by scent, in places a person cannot easily see into. Here is how the method works, and where it fits.

01Why finding the source matters

Rats and mice carry a range of bacteria and parasites, including salmonella and the bacteria that cause leptospirosis, and they spread them through droppings, urine and contact with surfaces and food. They also gnaw: through insulation, timber, packaging and the sheathing on electrical cables, which is a fire risk.

Signs such as droppings or noise tell you rodents are present, but not always where they are nesting or where they are coming in. Rats in particular can travel some distance through cavity walls, ceiling voids, ducting and broken drains. Treating where the signs appear, rather than at the source, often means a longer job and a problem that comes back.

02How detection dogs work

A dog's sense of smell is many times more sensitive than ours. Detection dogs are trained in much the same way as those that search for other substances: they learn a target scent and are rewarded for indicating where it is strongest. For rodents, that includes the smell of the animals themselves, their urine and droppings, the greasy smear marks they leave along regular routes, and nesting material.

Working with a handler, a dog can search a building systematically and indicate at a wall, a cupboard, a section of floor or a stack of stored goods. The handler then investigates that spot.

03Where the method is most useful

• Large or complex buildings such as warehouses and food storage sites, where a visual search of every void would take a long time.
• Sensitive areas where untargeted treatment is not appropriate, such as food storage, and where knowing exactly where to act keeps the use of rodenticides to a minimum.
• After treatment, as a check that an area is clear or that rodents have not come back.

Like any method, it has limits. A dog indicates where scent is strongest, which is not always exactly where the animal is, and old contamination can hold scent after the rodents have gone. The result still needs interpreting by someone who knows rodent behaviour and buildings.

04Other ways of finding the source

Detection dogs are not one of our standard services, but we have arranged a dog survey for customers in the past where a problem could not be traced any other way. Most rodent problems are traced without a dog. A careful survey of droppings, smear marks, gnawing and runs, monitoring points that show where activity is, and checks on drains, air bricks and service entries will find the route in on most properties. Where rats appear inside with no obvious way in, a drain survey often finds a broken or redundant pipe.