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Rats are among the most widespread pests globally, with certain species adapting remarkably well to urban and rural environments. These creatures, often referred to as "true rats," fall within the Rattus genus, and their adaptability, intelligence, and omnivorous nature make them resilient and challenging to manage. Below, we’ll explore the most common types of rats found in North America, along with the risks they pose and how to handle infestations.
There are two main types of rats that cause concern in the U.S. The Brown rat (or common rat) and the Black rat, which was introduced to this country, are common pests in both private homes and businesses.
(Rattus rattus)
Black rats, often referred to as roof rats, can be found in coastal towns and in many urban environments across the country.
The Roof rat (black rat) is slightly smaller and more agile than the brown rat. With a body length of about 6 to 8 inches, it has a sleeker, slimmer build, large ears, and a pointed nose. Roof rats are excellent climbers and tend to nest above ground in attics, wall cavities, and trees. Their long, slender tails help them balance, making them more adept at climbing and jumping than their brown rat counterparts.
Roof rats prefer warmer climates and, fittingly for a species sometimes called the ship rat, are more common in coastal or southern parts of North America. They’re particularly drawn to fruit trees, gardens, and outdoor vegetation, feeding on fruits, nuts, and grains. Like the brown rat, roof rats pose health risks, carrying diseases such as toxoplasmosis, cryptosporidiosis, and the bacteria responsible for the bubonic plague. Their climbing ability allows them to access food storage areas, making them a significant pest in homes and commercial properties with multiple levels.
(Rattus norvegicus)
Brown rats, also known as Norway rats or sewer rats, usually prefer ground living and burrowing, but sometimes they can be known to climb.
The brown rat is one of the largest rat species, with a body length of 7 to 9.5 inches, excluding its long, thick tail. They are robust, with coarse brown fur, small ears, and a blunt nose. Also known as Norway rats, they are known to burrow, creating networks of tunnels and nesting areas near food sources and shelters like basements, sheds, and under decks. This species is an adept swimmer and will enter buildings by moving through sewers or other ground-level entry points.
Primarily nocturnal, brown rats are highly adaptable and omnivorous, eating anything from grains to meat. Unfortunately, they also have a habit of gnawing on wood, plastic, and even electrical wires, which can result in fire hazards. Brown rats can spread diseases such as leptospirosis, trichinosis, and hantavirus, making them a public health concern when they establish infestations in homes or businesses.
Rats present a variety of risks to humans. They’re known carriers of pathogens that spread serious illnesses. Diseases such as leptospirosis, hantavirus, and trichinosis can be transmitted through their urine, droppings, and saliva, while rat bites or scratches can lead to infection. In addition to direct health risks, rats also bring fleas and mites into homes, potentially spreading additional parasites and diseases.
Structural damage is another risk. Rats constantly gnaw to keep their incisor teeth at a manageable length, often targeting wood, insulation, pipes, and electrical wiring. This gnawing behavior can cause significant property damage, especially when rats burrow into structural supports, chew through plumbing, or damage electrical systems. Such damage creates a fire risk and can require costly repairs. Additionally, rats contaminate food sources, leading to food waste and increased risk of disease transmission from contaminated items.
When dealing with rat infestations, quick action is essential. Both Norway rats and roof rats reproduce rapidly, leading to large populations that become difficult to manage over time. An infestation requires a strategic approach to eliminate the rats, address the entry points, and prevent re-infestation.
To manage an infestation effectively, start by identifying the signs of rats in your home or business. These signs include droppings, gnaw marks, and burrows or grease trails along walls and baseboards. Noise, especially at night, can also indicate rodent activity. Once you've confirmed an infestation, consider the following steps:
For more information, see our article on how to get rid of rats.
Preventing future infestations is key to long-term rodent control. Even after an infestation is removed, steps must be taken to keep rats from returning.
Avoid leaving pet food outdoors and clear away food waste. If you have fruit trees, pick up fallen fruit regularly. Compost areas should be covered and managed to minimize access by brown and black rats, as well as other rodents like the marsh rice rat (Oryzomys) that might also be attracted to food waste.
Rats look for safe places to nest, such as woodpiles, sheds, and basements. Keep woodpiles off the ground and away from your home, and secure sheds and other outdoor buildings. Roof rats are known to climb, so trim trees and shrubs near your house to prevent easy access to the roof or attic.
Rats can enter buildings through openings as small as half an inch. Regular inspections of your property, especially in attics, basements, and crawl spaces, can help you spot and seal new entry points before rats find them.
See our article on how to keep rats away for more detailed information on rat prevention.
Rat infestations can quickly get out of control due to the high reproductive rate of rat populations. If you notice signs of a rat problem, such as droppings, gnaw marks, or unusual noises, it’s crucial to take action immediately. Ehrlich Pest Control can assess your situation, provide detailed rat information, and recommend appropriate treatment options, including safe and effective rat extermination methods.
In summary, whether you’re dealing with brown rats, roof rats, or other rodents like wood rats (Neotoma), taking proactive measures and, when needed, contacting a professional can save you time and money and allay health-related concerns.