Scratching in the Walls at Night
By Marcus Ellery, Pest Control Editor · Updated October 2026 · General information, not an inspection or a diagnosis
The time of day you hear it is one of the better clues. UC IPM says house mice and both common rats are mostly active at night, and the Internet Center for Wildlife Damage Management says the same of flying squirrels, while gray and fox squirrels are mostly active by day. Bats can be heard scratching and crawling too, especially around dusk and dawn. Identifying the animal before sealing or poisoning anything matters, because the wrong first move can trap an animal inside the wall.
What people usually describe
- Light scratching or skittering inside a wall or ceiling after the house goes quiet.
- Gnawing or chewing sounds at night from one spot.
- Heavier thumps or rolling sounds overhead in the attic.
- Scratching and squeaking near dusk or dawn from a wall near the roofline.
- Noises that stop for a while after you bang on the wall, then start again.
Animals the sources describe as active at night
These are the possibilities the cited agencies and university extension services describe for this complaint. They are not ranked by likelihood, because none of the sources rank them, and only an identification of the actual specimen settles which one you have.
House mice
Most active at night, though sometimes seen by day. They get through openings as small as 1/4 inch.
Source: UC IPM
Roof rats
Mostly nocturnal. They usually nest above ground, and indoors that means attics, wall voids and ceiling voids. ICWDM says attic sounds are often the first sign of them.
Source: UC IPM
Norway rats
Also mostly nocturnal, but they burrow near foundations and tend to occupy basements and ground floors rather than upper walls.
Source: UC IPM
Flying squirrels
Unlike other tree squirrels, they are active at night. ICWDM puts their entry holes at about the size of a quarter, often with stains below attic vents.
Source: ICWDM
Bats
ICWDM lists vocalizing, grooming, scratching and crawling in attics and walls, especially on hot days before dusk and at dawn, along with a musty odor from droppings.
Source: ICWDM
Raccoons
They need only about a 4-inch gap and will sometimes tear off shingles or fascia boards to get into an attic or wall.
Source: ICWDM
How to find out
- 1
Write down when you hear it
Night points toward mice, rats or flying squirrels. Daytime noises fit gray and fox squirrels, which ICWDM says are mostly active by day. Dusk and dawn fit bats. (ICWDM)
- 2
Measure the entry holes outside
ICWDM gives baseball-sized holes for gray and fox squirrels, golf-ball-sized for red squirrels and quarter-sized for flying squirrels. UC IPM says mice get through 1/4 inch. (ICWDM)
- 3
Look for gnaw marks and rub marks
UC IPM describes rat tooth marks of about 1/6 inch against a mouse’s scratchy 1/12 inch, and greasy smudges where rat fur rubs along regular routes. (UC IPM)
- 4
Check the droppings
Droppings are the most reliable clue to which animal it is. See the household droppings guide, and follow the CDC cleanup steps before touching any.
- 5
Get a free or low-cost identification
Most state Cooperative Extension services, run through land-grant universities, will identify an insect from a specimen or a clear photo, often free or for a small fee. Some university labs, such as Cornell’s Insect Diagnostic Laboratory, take public submissions directly. Find your state’s land-grant university through the USDA NIFA land-grant university directory.
Try this while you wait
A trail or motion camera aimed at the suspected entry point shows what is going in and out before you decide anything, and a flashlight helps you find gnaw and rub marks. We do not list poisons or baits here: an animal you have not identified should not be poisoned inside a wall. These are screening and interim tools only. None of them identifies the pest for you or stands in for a licensed professional or an extension identification. As an Amazon Associate we may earn from qualifying purchases. It never changes your price.
When to stop and call a licensed pro
- It might be bats. ICWDM and the New Jersey Division of Fish and Wildlife both say exclusion has to be timed so flightless young are not sealed inside. Bats are protected in many places, so check with your state wildlife agency or a licensed wildlife control operator before doing anything.
- You are about to seal holes. Make sure nothing is still inside first, or the animal can die in the wall. See the dead-animal smell guide for what that leads to.
- You are considering ultrasonic plug-ins. UC IPM says there is little evidence sound, magnetic or vibration devices drive out established mice or rats.
- Raccoon-sized damage at the roofline. That is a wildlife-removal job.
If it turns out you need treatment
National 2026 planning ranges from our calculators for the jobs this page most often leads to. Open one to price your own home. Not quotes, and not lab-tested.
| Job | Typical 2026 range |
|---|---|
| Mice & Rat Removal cost calculator | $150 to $1,000 |
| Rat Exterminator cost calculator | $170 to $1,100 |
| Squirrel Removal cost calculator | $300 to $1,500 |
| Raccoon Removal cost calculator | $200 to $1,500 |
| Bat Removal cost calculator | $400 to $2,000 |
Local help
We do not recommend or rate pest control companies. Two neutral places to start:
- State pesticide regulatory agencies (NPIC directory): the state agencies that certify pesticide applicators. EPA advises confirming a pest control company’s license is current before hiring.
- USDA NIFA land-grant university directory: filter by state to reach your Cooperative Extension service, which can identify a specimen.
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Related identification guides
Frequently asked questions
Is scratching at night more likely mice or squirrels?
Of the common culprits, UC IPM says mice and rats are mostly nocturnal, and ICWDM says gray and fox squirrels are mostly active by day. Flying squirrels are the exception: they are squirrels and they are active at night.
Should I put poison bait in the wall?
UC IPM notes that mice usually stay within about 30 feet of their nest, so poisoned mice often die inside the structure and cause an odor problem. It says trapping lets you remove the mice and may be the best approach when odor is a concern.
Do ultrasonic repellers stop the noise?
UC IPM says there is little evidence that sound, magnetic or vibrational devices drive established mice or rats from buildings, and that rats quickly get used to repeated sounds.
Can I just seal the hole I found?
Only after you know the animal is out. Sealing an occupied wall can trap it inside. For bats, ICWDM and New Jersey state wildlife guidance say exclusion must avoid the period when young cannot fly.
Sources
- UC Statewide IPM Program, Pest Notes: House Mouse (Pub. 7483)
- UC Statewide IPM Program, Pest Notes: Rats (Pub. 74106)
- Internet Center for Wildlife Damage Management, Tree Squirrel Biology
- Internet Center for Wildlife Damage Management, Tree Squirrel Damage Identification
- Internet Center for Wildlife Damage Management, Bat Damage Identification
- Internet Center for Wildlife Damage Management, Bat Damage Prevention and Control Methods
- Internet Center for Wildlife Damage Management, Raccoon Damage Identification
- Internet Center for Wildlife Damage Management, Roof Rat Damage Identification
- New Jersey Division of Fish and Wildlife, Bat Control guidance (PDF)
This page summarizes what the agencies and university extension services listed above publish about this problem. It is general information, not an inspection, a pest identification or medical advice, and it cannot tell you what is in your home. Sources can change; check the linked page before acting on it. PestCost is not affiliated with any agency, university or association cited here. Spotted an error? Send a correction. Product links are Amazon affiliate links; the quote button is a paid Angi referral. Disclosure.