Roof Rat

What Are They?

These pests get their name from their tendency to nest in high places, but you may not just find these 8-inch long creatures in your attic; they are also known to thrive in basement environments. There are serious health threats associated with having rats in your home, including dust-carrying Hantavirus, a deadly disease that is transmitted through their urine and droppings. Rats also pose serious threats to your pets including fleas and mites that they carry and bites if your pet finds them before you do.

What Do They Look Like?

roof rat

Roof rats possesse a sleek body with a tail that is hairless, scaly, and in total longer than the length of the body. In total, the rodent may reach seven to eight inches in length, while weighing up to 10 ounces. Other differentiating 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

Size: Roof rat (black rat, ship rat) adult head+body length is 6-8 in (16-20 cm ); tail length is 7-10 in (19-25 cm ); weight is about 5-9 ounces, up to 12 ounces

Color: Brown with black mixed in, to gray, to black on top with white; gray or black underside.

Characteristics: Soft, smooth fur; pointed muzzle; large eyes; large, almost naked ears which can be pulled over the eyes. Scaly, dark tail is longer than combined head+body length.

Where Do They Live?

As their name would imply, roof rats prefer to nest high off the ground in trees, vines growing along the sides of buildings, or in attics. They’re adept at climbing and can often be seen running along utility lines or tree branches. Roof rats in attics, typically get inside through upper level windows and cracks and crevices under roof eaves.

Damages Caused by Roof Rats

The most common form of damage caused by a roof rat in the attic is the tearing up of insulation to use as nesting. Likewise, their constant need to gnaw leads them to chew into structural beams and electrical wiring, which creates fire hazards. Additionally, the pests can spread diseases like leptospirosis, rat-bite fever, and plague. Roof rats in the attic will also leave feces, urine, tracks, and shed fur around the house, creating unpleasant odors.

Probably from southeast Asia, but now found around the world. In the U.S. Rattus rattus is most common in coastal and southern states, especially near seaports.

What Do They Eat?

Roof rats eat almost anything, but they prefer fruit, vegetables, and cereal products. They get their water often from their food. They eat a lot at one time, and will return to that place time after time. If they do not like a food or bait they quickly become shy of it.

Roof Rat Droppings

Identifying Roof Rat Droppings

roof rat poop
roof rat droppings

source: UFL.edu

It can be difficult to identify rats solely based on droppings. However, rat waste is unique from and much larger in size than smaller rodents that may infest homes. At about half an inch long, roof rat droppings are gray to black in color depending on how recent or old they are. Additionally, older waste is more likely to crumble and turn to dust whereas more recent feces will remain soft. Roof rats’ droppings resemble the shape of bananas, which is distinct from Norway rats’ poop.

Waste Health Hazard

All waste is unsightly and odorous, but roof rats’ droppings can also contain bacteria that is harmful to both humans and pets. In fact, rodents are responsible for spreading Hantavirus, which can be deadly to people. Other diseases transmitted to residents through roof rat droppings include lassa fever, leptospirosis, and salmonellosis. It is imperative that homeowners refrain from consuming foods that have been contaminated by rodent waste and to avoid cleaning up rat feces without proper protection.

Removing Roof Rat Droppings

In order to clean safely, it is important to wear gloves and masks so that bacteria cannot make contact with skin or accidentally be ingested. However, facemasks and gloves are not entirely effective against disease.

Life Cycle

Roof rats mature in 2-5 months, and are adults for 9-12 months. Pregnancy takes 3 weeks. Newborns get hair after 1 week, open eyes after about 2 weeks, are weaned at 3-4 weeks. Female has 4-6 litters per year, with 6-8 young per litter. They have keen hearing, smell, taste and touch (long whiskers), but bad vision, and are color blind. They are good at running, climbing, jumping, even swimming. They are nocturnal and explore a lot, but are cautious and shy away from new objects.

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.

Rats, in general, are known vectors of various diseases, and the roof rat is no different. Known diseases roof rats carry include bubonic plague, typhus, and salmonellosis, or food poisoning. 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 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.

Detection Checklist

  • Check for gnaw marks.
  • Watch out for droppings.
  • Look out for four-toed front footprints and longer 5-toed hindprints.
  • Be aware of dark, greasy markings that are the result of fur rubbing against surfaces.
  • Check under plants for shallow burrows.
  • Look outdoors for greasy runways along walls and bare soil runways.
  • Check for tiny nibbles in food.

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.

Learn more about using traps to manage an infestation.