Are Rats Spreading into the Philadelphia Suburbs?

Are there more rats in Delaware County, PA than there used to be?

We cannot point to a reliable count of rats in the suburbs, and anyone who quotes one should be asked where it came from. What we can say is that the conditions rats need are common in inner-ring neighborhoods: dense housing close to transit and commercial corridors, older sewers, alleys with shared trash storage, and backyards with bird feeders, compost and pet food.

When something disrupts an established population, such as a demolition, a road project or a sewer replacement, rats scatter into nearby yards. Homeowners on the next block suddenly see them for the first time, and it feels like an invasion even though the population simply moved.

What draws Norway rats into older suburban neighborhoods?

Norway rats need three things within a short distance of each other: food, water and a place to burrow. These are the attractants we find most often in yards and alleys:

• Bird feeders and the seed that collects on the ground below them
• Open compost piles, especially with kitchen scraps
• Trash cans without tight lids, or bags left out overnight
• Pet food bowls left outside and dog waste in the yard
• Backyard chickens and their feed
• Woodpiles, overgrown shrubs and clutter beside sheds and garages
• Leaking spigots, clogged gutters and low spots that hold water

Rat burrows and other signs rats are in your yard

Norway rats dig. Burrow entrances are usually a few inches across, with smooth, packed edges and a fan of loose soil spilled outside. You will find them along foundations, under concrete slabs and stoops, beneath sheds and decks, and at the base of fences and shrubs. An active burrow has no cobwebs or leaves across the opening.

Other signs include droppings about three-quarters of an inch long with blunt ends, greasy rub marks along walls and fence lines where rats travel, gnaw marks on wooden doors and plastic bins, and well-worn paths through grass. Rats are also cautious of new objects, which is one reason a trap set yesterday often sits untouched.

Norway rat or house mouse? How to tell

The two need different approaches, so it helps to know which one you have:

When do rats show up most in Delaware County yards?

Norway rats breed all year when food and shelter hold out, and one female can raise several litters in a year, so a handful of rats in April can be a colony by October. The seasons mostly change where you notice them.

• Spring: new burrows open along foundations and under sheds as the ground thaws, and freshly turned garden beds get dug into.
• Summer: activity spreads to vegetable gardens, fallen fruit, compost and grills, with rats moving at dusk along fence lines.
• Fall: as gardens finish and nights cool, rats work closer to buildings, and gnawing at garage and basement doors picks up.
• Winter: rats that got inside stay in basements, crawlspaces and wall voids near heat. Outside, tracks in snow lead straight to the burrow or gap.

Rats after construction and sewer work

Large building projects, demolition and sewer or water line replacement are among the most common triggers for sudden rat activity in an established neighborhood. Digging and vibration break up burrows, and loss of the old food source sends rats looking for new ones nearby.

If a project is starting near you, tighten up before it begins: secure trash, take bird feeders down for a while, clear clutter from beside the house and seal any foundation gaps. It is far easier to keep displaced rats from settling in than to remove them after they do.

Rats in a shared alley: why one yard cannot fix it alone

On attached-home blocks, rats rarely belong to one property. A burrow under one garage can feed on trash from three houses down, and trapping on a single lot often just opens room for rats from next door. Results come faster when neighbors work on the same conditions during the same few weeks.

• Agree on a trash routine: lidded cans, nothing bagged on the ground, cans pulled back in after pickup.
• Take bird feeders down across the block for a season, not just at one house.
• Report a vacant lot or empty house with open trash or overgrowth to the township or borough code office. Many Pennsylvania municipalities enforce a property maintenance code that addresses rodent harborage.
• Tell each other where burrows appear, so traps or bait stations go on the runways rats actually use.
• If a storm drain or sewer cleanout looks like the source, report it to the municipality's public works department rather than baiting next to it yourself.

What shuts rats down

1. 1

   Remove the food

   Take away feeders, secure trash and compost, bring pet food in, and clean up fallen fruit and seed.

2. 2

   Remove the shelter

   Clear clutter and woodpiles from beside the house and trim shrubs up off the ground so burrows are exposed.

3. 3

   Reduce the population

   Use traps or tamper-resistant bait stations placed along runways, away from children, pets and wildlife.

4. 4

   Seal the building

   Close gaps of half an inch or more around foundations, doors, vents and utility lines with metal and mortar.

5. 5

   Monitor and follow up

   Check burrows after treatment by lightly filling them with soil; reopened burrows mean rats are still active.