Roof Rats

Get Rid of Roof Rats in Your Home or Business

General Information

What is a Roof Rat?
Black rats (Rattus rattus), also known as roof rats, are not native to the United States, having arrived in the New World aboard European trade ships in the 17th and 18th centuries. Other common names for the species include ship rat and house rat, due to the affinity of the species to live amongst humans and inhabit ships.

Avid climbers, roof rats typically frequent attics, rafters, and in-between ceiling joists as opposed to living near the ground. The rodent may be confused with the Norway rat, Rattus norvegicus, which is known to inhabit sewers and remains the more aggressive of the two species, having displaced the roof rat in certain areas of the United States.

Picture of Roof Rat
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Appearance & Identification

What Does a Roof Rat Look Like?
Rattus rattus possesses a sleek body with a tail that is hairless, scaly, and in total longer than the length of the body. The roof rats’ body may reach seven to eight inches in length, and weigh up to 10 ounces.

Other prominent features include a pointed snout and large ears. Coloration ranges from dark brown to black with a lighter underbelly. Some scientists believe roof rats adapt to match surrounding colors of their habitat.

Habits/Habitat

Like other species of rats, roof rats are more active at night. As nocturnal animals, the rodents may be easier to locate and control during late hours. Agile climbers, roof rats tend to forage for food above ground and utilize tree branches and utility lines in order to enter domiciles in search of food. The rodents build nests in secluded areas above the ground, such as in hollow tree cavities, attics, storage areas, and in vine coverage on buildings.

Roof rats can swim but do not spend much time in sewers, unless it is to move between areas. In New England, roof rats tend to hug coastal regions, as ships remain the most common vessel the species uses to spread and disperse into human populations. Roof rats have even adapted to living in colder climates.

Diet

What Do Roof Rats Eat?
Omnivorous by nature, roof rats may feed on fruit, dates, insects, snails, stored foods, and garbage. The rodent consumes around 15 grams of food each day and draws most of its water content from food sources. Roof rats are also known to gnaw through synthetic materials such as wiring, insulation, and wood while foraging for food and excrete waste on those same materials.

Reproduction

Explaining the Roof Rat Life Cycle
A polygamous species, R. rattus typically has a dominant male that mates with multiple females in the colony. Breeding may continue all year if climate and environmental conditions allow, with females producing up to five litters a year. In New England, where cooler climates persist, roof rats experience peak breeding seasons in the summer and fall.

Young rats are able to start reproducing within three to five months of their birth. Gestation periods last up to 30 days, and as mammals, rats must nurse for the first three to four weeks of their lives.

Young rats remain hairless through much of the nursing period and typically do not open their eyes for the first 15 days of life. Rats tend to live in the nest until reaching full adulthood with a total life span of around one year in the wild.

Problems Caused by Roof Rats

As scavengers, roof rats destroy the food source as they eat, doing massive damage to farms, livestock, and stored food/products. Roof rats also destroy containers and food-packaging materials, as well as building foundations through burrowing, gnawing, and appropriating for nest-making.

Diseases
Rats, in general, are known vectors of various diseases, and the roof rat is no different. Known diseases roof rats carry include:

  • Bubonic plague
  • Food poisoning
  • Salmonellosis
  • Typhus
The rodent also urinates and defecates on foodstuffs, further contaminating materials for human consumption. Additionally, rats may carry fleas and other internal and external parasites that could lead to cross-contamination between humans and pets.

Signs of a Roof Rat Infestation

As roof rats generally stay off the ground with the inclination to climb, smudge marks along rafters and ceiling joists are usually the first signs of an infestation. The smudge marks are a direct result of dirt and oil found in rat fur, which leave a trail when a rat rubs against the wood.

Finding droppings, urine marks, and actual tracks may pose an issue, since roof rats tend to move around high up, though homeowners may still locate such signs. One of the best indications as to whether or not the home or business may face an infestation lies in sound, as scurrying noises in the attic or beams at night may indicate the presence of roof rats.

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Prevention

To avoid infestation, sanitation measures must occur continuously. Reduce available shelter and food sources, fill gaps in foundations, walls, and attics, and consistently gather and store garbage in containers with secure lids. Ensure that all screens, windows, and doors fit securely and that all vegetation that may provide access to the home/building remains trimmed and does not overhang roof or eave access.

The best line of defense for home and business owners remains traps. A variety of options, such as live bait traps, glue boards, electrocution traps, and rodenticide baits, are available at local hardware and big box stores. While trapping may help with roof rat infestation, most store-bought devices require multiple applications in order to fully eliminate pest problems and may become expensive and time-consuming.

Also, because rats are vectors of multiple diseases, proper disposal methods must be followed. Contacting professionally trained pest control experts typically alleviates such problems.