Rats in Baltimore Alleys and Yards: How They Live and What You Can Control

Why are there so many rats in Baltimore alleys?

Rats live where they can find food, water and shelter close together. Baltimore's rear alleys concentrate trash containers, back doors, cellar windows and drains in narrow strips behind rows of attached houses. The city's waterfront and stream valleys add more shelter and water, so the pressure is high in many neighbourhoods.

The Norway rat, also called the brown rat, is the species most people mean when they talk about city rats. It digs burrows, often along foundations, under slabs, concrete steps and loose paving, and it can live in cellars and walls. It is a big, adaptable animal, and it does well wherever people leave food.

Baltimore's layout helps explain the problem. Most of the city is built as attached brick rowhouses in long rows, and behind each row runs an alley. That is where trash cans, bulk items and food waste end up, and where cellar doors and windows face. The harbour and the stream corridors, such as Jones Falls and Gwynns Falls, add water and cover. We cannot say the streams cause rat problems on their own, but a rat that finds a wet, sheltered edge next to food has what it needs.

How bad it is varies a great deal by block and even by house. One alley can have steady rat traffic while the next stays quiet, often because of what is being left out.

What did the city's Rat Rubout programme report?

In an August 2015 press release, Baltimore's Department of Public Works said its Rat Rubout crew had grown from eight to 16 technicians and planned to inspect and treat every alley on a 20-day cycle instead of 40. The plan covered 12,250 alleys totalling 4,555 miles. That is a 2015 report, not a current figure.

The 20-day cycle was chosen with rat biology in mind. Norway rats have a gestation of roughly three weeks, so returning to an alley every 20 days is meant to catch each generation before the next one is born. The logic is the same one a private technician uses when scheduling follow-up visits.

We have not been able to find a current figure for how many staff the programme has or how often alleys are treated today, so please read the numbers below as a snapshot of what the city said in 2015.

The takeaway for a resident is simple. Alley treatment by the city handles the public side of the problem. What happens at your own back door, cellar window and trash container is still your side of the line, and a city crew cannot seal a gap in your foundation.

How do rats get from the alley into a rowhouse?

Rats move from the alley into a house through gaps at or near ground level: cellar windows, damaged vents, gaps around pipes and cables, rotten door sweeps and cracks in old foundations. Once inside a cellar, they can reach walls and party walls and travel to neighbouring houses. Finding and sealing those gaps is the lasting fix.

A rat's body is more flexible than most people expect. It can squeeze through a gap much smaller than its body looks, and it gnaws, so wood, soft sealant and thin plastic are not barriers. A technician looks for rub marks, which are greasy smears along regular paths, along with droppings, gnaw marks, burrows beside the foundation and signs of nesting.

Common entry points on a Baltimore rowhouse include old coal chutes and cellar windows, where a broken pane or a loose screen leaves an opening, gaps where gas, water and cable lines pass through the wall, and rear doors that do not seal at the bottom. Where one house joins the next, a shared cellar wall or a gap in the party wall can carry rats along the block. We explain how that works in rowhouse party walls and pests.

If you hear scratching in the walls at night, find droppings in a cellar or see a rat in the house during the day, treat it as an indoor problem and call for an inspection. During the day, a visible rat can mean the population is large.

What signs tell you rats are active at your address?

Look for droppings, greasy rub marks along walls, gnawed food packaging or wood, burrow holes beside foundations and steps, and noises in walls or ceilings at night. Several signs together point to an established problem. A single dropping may be old, so note where and how fresh it looks and share that with the technician.

Signs outside the house are worth as much as signs inside. Walk the alley and the back yard with a flashlight at dusk. Burrow entrances near a fence line, a shed or the base of a back step, with smooth, packed-down earth around them, usually mean rats are using the spot. Chewed corners on a trash bag or a torn lid are another clue.

Inside, check the cellar first, then the kitchen cabinets under the sink and the back of the stove. Pipes that pass through walls are highways, so look at the gap around them for dirt smears and droppings. Do not sweep or vacuum dry droppings, because that can stir up dust. Wear gloves, dampen the area and wipe it up, or leave it for the technician.

Take photos, note the date, and mark where you found things. A technician can read a pattern from that information: droppings concentrated by a cellar window point to that window, while scattered signs in the kitchen suggest a path through the walls.

What can a homeowner or renter control?

You control food, access and sanitation at your own property. Use trash cans with tight lids, never leave bags out overnight, remove pet food and bird seed from the ground, clear clutter and seal gaps. These steps starve and exclude rats, and they work alongside professional treatment, not instead of it.

Rats are opportunists. If you remove what they are eating and where they are hiding, you push them to look elsewhere, which is why this advice shows up in every public health guide on the subject. Start with the places that matter most in a Baltimore rear yard or alley.

• Use rigid, lidded trash containers and keep the lids closed. Bags on the ground or in a damaged can are an easy meal.
• Put trash out on collection day, not the night before.
• Clean up after pets and grills, and do not leave pet food outside.
• Pick up fallen fruit and nuts, and keep bird feeders off the ground or remove them while rats are active.
• Clear stored boxes, wood piles and clutter that touch the foundation or fence, since they offer cover.
• Fix leaking spigots, drains and downspouts so there is no standing water.
• Seal gaps with rodent-resistant materials such as metal mesh or hardware cloth and cement or other materials a technician recommends, not foam or soft filler alone.

When do rats cause more trouble in Baltimore?

Rats are active all year, and their pressure on a house changes with the weather. They can breed through mild spells, and as nights cool in autumn and winter they look for warm, sheltered spaces such as cellars and rowhouse walls. Hot, dry summers can push them toward water and food, which means trash and drains.

None of this follows a strict calendar, and Maryland's weather swings a lot. Average annual precipitation at BWI is about 43.6 inches, summers are hot and humid, and January lows average in the low to mid 20s Fahrenheit, which is cold enough to push rodents toward heated buildings. Our Baltimore pest calendar breaks the year down by month.

If you notice activity in autumn, treat it as a signal to check gaps before winter. Rats and mice that move into a cellar in November can be hard to dislodge in February.

What does professional rat control involve?

A technician inspects the exterior and cellar, identifies burrows and entry points, places traps or bait stations where rats travel, advises on sanitation, and seals or recommends sealing gaps. Rats are cautious, so follow-up visits are normal. The goal is to remove the animals and the way in.

Professional rat control usually starts with finding out where the rats are living and travelling. Burrows beside foundations, gnaw marks, droppings along walls, and smear marks help show their routes, and bait stations or traps go where they will meet them. Because rats avoid anything new in their territory at first, it can take a few days before they feed or enter a trap, which is part of why a single visit is rarely the whole job.

Sealing matters because bait alone does not stop new rats from moving in. If the gap is still there next month, another animal will use it. Where the house is attached, a technician may also look at the shared walls, as in rowhouse pest proofing. If you are seeing smaller droppings and chewed food boxes, it may be mice instead, and mouse control covers that. Rats and mice are often confused, and a technician can tell them apart from the droppings. To describe what you are seeing, call (855) 974-4733.