Why Rats Come Back After an Exterminator

The entry points are still open

This is the big one. Rats leave scent along their routes. When the rats inside are gone, others nearby still follow that trail. If the soffit gap, the gable vent or the crawl space vent is still open, they walk right in.

University of California guidance recommends sealing openings larger than a quarter inch with steel wool, wire screen or sheet metal, and using galvanized half-inch mesh on vents. Ask your provider for a list of every opening sealed and the material used. See rodent exclusion.

Only some openings were sealed

A house can have a dozen openings. Sealing the obvious ones and missing a roof return, a plumbing vent boot or a gap behind the gutter leaves a door open. Older Memphis homes, with multiple additions and wood soffits, are especially prone to this.

Ask the provider which openings they did not reach or seal, so you know what is left.

The yard still feeds them

University of California guidance says roof rats routinely travel 300 feet or more for food, and Norway rats forage about 100 to 500 feet from the nest. If your yard has a bird feeder, pet food on the porch, fallen pecans or a garbage cart that does not close, rats nearby have a reason to keep testing your house.

Firewood against the house, ivy on walls and limbs touching the roof give them cover and a route in. See the trash and property guide.

The neighbors have rats

Rats do not stop at property lines. A vacant house, an overgrown lot, a restaurant dumpster or a neighbor's chicken coop can keep supplying rats to the block. Sealing your house protects you even if the source is next door.

For outdoor rat problems coming from other properties, Shelby County's rodent control program takes complaints, and Memphis 311 takes code issues like abandoned houses. See the reporting guide.

Bait without trapping or sealing

Bait-only treatments can reduce numbers, but they do not close openings. They can also leave dead rats in walls and attics. University of California guidance warns that rodenticides are toxic to pets and people and recommends sealing entry points before baiting outdoors so poisoned rats do not die inside.

A plan that combines trapping inside, sealing and outdoor stations where appropriate tends to last.

The job ended too early

Trapping should continue until catches stop and no fresh droppings appear. Pulling traps after the first few catches can leave a few rats behind, and roof rats breed fast; the TWRA notes litters of 6 to 12 and up to 5 litters a year.

A final check a week or two after sealing confirms the job. If new droppings show up, call the provider back early.

New construction and demolition nearby

Sometimes the source is a change nearby. Demolition of an old building, clearing of a wooded lot, or new construction can push rats out of their old homes and into the closest houses. Road and sewer work can do the same.

If rats show up after a long quiet period, look around the block. If a nearby site is clearly the source, report outdoor rodent activity to the county program, and focus on keeping your own house sealed.

Changes in your own yard

Small changes at home can bring rats back too: a new bird feeder, a dog food bin in the garage, a compost pile, a stack of lumber from a project, or a fruit tree that started bearing. Each adds food or cover.

When rats return, think about what changed in the last few months. Fixing that, along with checking the seals, often solves it.

It also helps to walk the outside of the house twice a year, in spring and late summer, looking for new gaps, damaged vent screens, chewed seals and limbs growing back toward the roof. Small repairs caught early keep a sealed house sealed.

What to ask for next time

When you call a provider, ask:

• Will you seal entry points, or only trap and bait?
• Which openings will you seal, and with what materials?
• How many follow-up visits are included?
• What happens if rats come back within a set time?

Get it in writing. See rat control and the cost guide.