Roof Rat

Also known as the black rat, the roof rat (Rattus rattus) has a smaller body than brown rats and are distinguished by their longer tail, which exceeds the length of their body. They weigh anywhere between 75 and 230 grams as adults and are typically black in colour. Their fur is also shorter and sleeker and their ears are larger than those of brown rats.


While many other rat species survive mainly on high-protein meals like meat scraps, roof rats prefer to consume fruits and nuts, making them similar to squirrels in terms of diet. However, like most rodents, roof rats are omnivorous and when hungry enough, will also eat:

  • Dog and cat food
  • Garden vegetables
  • Tree bark
  • Insects
  • Paper

They will readily enter homes and commercial buildings in search of food and water, and won’t hesitate to damage property (e.g. chew open boxes and containers) to access stored food. Roof rats will also chew pipes to get water, which can cause major structural damage to your home.

Where to find them

Although the roof rat’s specific origins are unknown due to their pervasiveness, there is evidence that they were present in prehistoric Europe and Southeast Asia. By spreading bacteria in the fleas on their bodies, they played a primary role in the spreading of the Black Death.

Today, they can be found in or around many urban areas. Unlike brown rats, roof rats are excellent climbers and will build nests above ground. Outside, they will nest in wood piles, shrubs and dense vegetation. Indoors, they seek out attics, false ceilings and other higher spaces where heat tends to rise.

Reproduction rate

Female roof rats can start having litters at three or four months of age. They generally have up to three litters of five to eight babies every year, so once roof rats take up residence in your home, it won’t take long for them to multiply.

Common diseases

There are many diseases that roof rats can transmit to humans. Depending on the condition, they can be transmitted through the animal’s droppings, urine, bites, and mites or fleas in their fur. They include:

  • Leptospirosis, which can cause liver and kidney failure or meningitis if left untreated
  • Plague
  • Typhus
  • Salmonellosis 
  • Rat-bite fever

Signs of an infestation

Even if they’ve invaded your home, you won’t necessarily encounter roof rats because they are nocturnal and search for food at night. There are, however, other ways to detect an infestation. They include:

  • Droppings, which are smaller than those of brown rats
  • Scratching noises in your attic, ceilings or walls
  • Dirt and grease marks from their fur along baseboards and other regularly-used routes
  • Nests and chewed insulation in exposed walls (e.g. in the attic)
  • Chewed food boxes in your kitchen
  • Gnawed paper and electrical wires throughout your home

How to keep them out of your home

If you’ve noticed signs of roof rats outside your home (droppings, missing food from pet dishes, gnawed fruit that has fallen from trees), take the following measures to prevent them from getting into your home:

There are steps you can take to keep a brown rat infestation out of your home. They include:

  • Seal all openings around wires, cables, and pipes that enter through your foundation or the falls
  • Repair any torn screens on doors or windows
  • Apply weather seals to all windows and doors leading outside
  • Use weather strips to seal any gaps beneath your garage doors and keep side doors closed, particularly at night
  • Refrain from leaving food lying around in the kitchen
  • Keep all food in secure containers or the fridge
  • Remove all standing sources of water
  • Cover any waste stored outside, such as compost and garbage containers

Need roof rat control services?

If you’ve noticed any signs that roof rats may be taking up residents in your home, you may be able to prevent an infestation by buying poison, traps, or repellants (scent-based or ultrasonic). It is important to note that rats are wary of anything new and may avoid your control measures for awhile, enabling their numbers to grow before your DIY tools take effect.

At Action Pest Control, we have the resources and experience to help eliminate roof rats from your home. We provide 24/7 assistance to homeowners in and around Hamilton, Burlington, and Oakville, so don’t wait to seek the professional assistance needed to keep your home secure and your family safe and healthy. When you need a pest control company you can trust, contact us to find out how we can help.