Los Angeles has one of the worst rat problems in the United States, ranking #2 on Orkin’s list of most rat-infested cities for seven consecutive years. The city’s mild climate, dense housing, and abundant food waste create near-perfect conditions for two species that thrive alongside humans: the roof rat and the Norway rat. If you live in LA, understanding which rat you’re dealing with and how they get inside is the first step toward keeping them out.
Two Species, Two Strategies
The roof rat is the more common pest across much of Los Angeles. It’s smaller and sleeker than its cousin, with a tail longer than its head and body combined. Roof rats are excellent climbers. They nest above ground in trees, dense shrubs, attic spaces, wall voids, and false ceilings. At dusk, you might spot them running along utility lines or fence tops.
The Norway rat is stockier and prefers life at ground level. It digs burrows along building foundations, beneath trash piles, and in woodpiles. Indoors, it stays in basements and ground floors. When both species occupy the same building, they typically split territory: Norway rats claim the lower levels while roof rats take the upper floors.
Knowing which species you have tells you where to focus. Scratching sounds overhead at night usually point to roof rats. Burrow holes along your foundation or gnaw marks at ground level suggest Norway rats.
Why LA Has Such a Big Rat Problem
Southern California’s urban centers provide ideal habitat: abundant food, water, and shelter year-round. Unlike cities with harsh winters that naturally suppress rodent populations for a few months, LA’s mild climate lets rats breed continuously. A single pair can produce dozens of offspring in a year, and those offspring start reproducing within a few months.
Food waste is a major driver. Overflowing dumpsters, unsecured trash cans, and piles of cardboard behind restaurants all serve as buffets. Fruit trees are another factor unique to Southern California. Citrus, avocado, and other backyard fruit that falls to the ground or stays unharvested on the branch draws roof rats directly to residential properties. Palm trees with dense, untrimmed canopies offer ready-made nesting sites high above the ground.
Infrastructure plays a role too. LA’s older housing stock has more gaps, cracks, and deteriorating vents that give rats easy entry points. Rats can squeeze through openings as small as a quarter, roughly half an inch across.
Flea-Borne Typhus Is a Real Concern
Rats in Los Angeles carry fleas that transmit flea-borne typhus, a bacterial illness that has been rising sharply. LA County documented an all-time high of 220 cases in 2025, continuing a sustained upward trend since 2010. Clusters have been concentrated in Central and South Los Angeles, though cases occur countywide. The disease peaks in late summer and fall but shows up year-round.
Typhus spreads when infected flea droppings get rubbed into cuts, scrapes, or the eyes. It doesn’t pass from person to person. Rats aren’t the only carriers of infected fleas: free-roaming cats, opossums, and outdoor pets can also bring them into contact with people. The animals themselves don’t get sick.
Symptoms start within two weeks of exposure and include fever, headache, muscle pain, nausea, and a rash that spares the palms and soles. Most cases are mild and treatable with antibiotics, but severe cases can require hospitalization. In rare instances, the infection can cause swelling around the brain lining or heart valves. LA County reported its first typhus deaths since 1993 in 2022, a reminder that the disease, while usually manageable, is not harmless.
Rat-Proofing Your Home
Exclusion is the most effective long-term strategy. The goal is to seal every opening a rat could use, and that means anything half an inch or wider. Start with a walk around the exterior of your home, checking foundation vents, gaps where pipes and wires enter walls, roof eaves, and the edges of garage doors. Don’t forget dryer vents and crawl space openings.
The material you use matters. Standard caulk and expanding foam won’t hold up; rats gnaw through both. For lasting results, use galvanized hardware cloth with half-inch mesh for rats or quarter-inch mesh if you also want to keep mice out. Stainless steel or vinyl-coated welded wire mesh is even more durable and won’t rust over time. Galvanized sheet metal (24-gauge or heavier) works well for pipe barriers and kick plates at the base of doors. For any concrete repairs, use at least 2 inches of reinforced concrete or 3.75 inches unreinforced.
Install corrosion-proof wire mesh screening with quarter-inch openings over all vent openings. Attach metal barriers with screws rather than staples so larger animals can’t pull them loose.
Yard Maintenance That Actually Helps
Roof rats nest in dense vegetation, so thinning trees and shrubs near your home reduces shelter. This is especially important for fruit trees. Pick ripe fruit promptly, collect anything that drops to the ground, and remove dead wood from citrus and avocado trees where rats build leaf-and-twig nests. Keep palm trees trimmed so dead fronds don’t accumulate into thick canopies.
Eliminate debris and woodpiles, or store materials neatly off the ground. Thick mulch layers can also harbor rats, particularly in hot weather when they dig shallow burrows underneath for cooler shelter. Use secure, rat-proof containers for trash and compost. Piles of cardboard, common in alleys and garages, are a magnet for nesting.
Trim any tree branches that overhang your roof or touch utility lines near your house. Roof rats use these as highways to reach upper stories. Even a few feet of clearance between branches and your roofline can make a significant difference.
Reporting and Public Resources
If you rent a home in Los Angeles County and have a rodent problem, you can report it by calling 888-700-9995 or filing a complaint online through the LA County Department of Public Health. An inspector may visit your home and determine whether the property owner is legally required to address the issue. Landlords in LA County have a responsibility to maintain habitable conditions, and active rodent infestations fall outside that standard.
LA County’s vector control program also monitors areas with high rodent and flea activity, particularly in neighborhoods where typhus cases cluster. Keeping rats off your property isn’t just about comfort or property damage. In a county where flea-borne typhus cases have more than doubled in recent years, it’s a meaningful public health measure.