Why Do Rats Keep Returning to the Same March Property?

There is a version of recurrence where the route in is known, the treatment was competent and the proofing was done — and it still comes back. Frequently the answer is that the problem was never really indoors.

Indoor Activity as a Symptom

Rats living outdoors on a property — under decking, in a bank, beneath a shed, in dense cover along a boundary — are a standing population with a supply of individuals looking for somewhere better. A building is somewhere better, particularly once the weather turns.

So treating indoors removes the ones that came in. It does nothing about the ones that will.

How to Tell There Is an Outdoor Population

• Burrows. Holes roughly golf-ball sized or larger, often with fresh spoil, usually against a wall, under decking, in a bank or beside a shed base
• Runs. Flattened tracks through vegetation, worn enough to show, usually following an edge
• Droppings outdoors, on decking, a path, a patio or in a shed
• Gnawing on outbuildings, shed doors, or stored goods
• Daytime sightings outdoors, which usually indicate enough competition to push some out in daylight
• Activity around a compost heap, a feeder or a chicken run

Where the Reservoir Comes From

• Food. Spilled bird seed, open compost, fallen fruit, bins on the ground, animal feed
• Harbourage. Decking voids, sheds on bearers, log piles, dense cover, rubble
• Adjacent land. Open ground, a watercourse, farmland, allotments, or a neglected neighbouring garden
• Water, which in a garden with a pond or a leaking outside tap is one less reason to go elsewhere

What Treating It Properly Involves

1. Survey the outside as seriously as the inside — boundaries, decking, outbuildings, compost, feeders, drainage covers.
2. Deal with the food and the harbourage, which is the part you can do for nothing and the part that lasts.
3. Treat the outdoor population where there is one, with placements appropriate to an outdoor setting and to whatever else forages there.
4. Treat indoors.
5. Proof the building once it is confirmed clear.

Where the reservoir is on land you do not control — a neighbour's garden, a yard, open ground — we will say so. Proofing the building becomes the more important half of the job in that situation, because the outdoor half is not yours to fix.