Roof rats are a persistent threat to food processing, grocery, pharmaceutical, and food service industries—and because of their agility and preference for hidden, elevated spaces, they can be incredibly difficult to control. Also known as black rats or ship rats, they damage goods, contaminate surfaces, and put health standards at risk. Accurate roof rat identification is essential to limit business disruption and stop infestations before they trigger failed audits, product recalls, or regulatory shutdowns.
Color: Black
Legs: 4
Shape: Long
Size: 16 inches total (6-8 inch body plus 6-8 inch tail)
Roof rats are slim, lightweight rodents measuring six to eight inches in body length, with a long, scaly tail bringing their total length to up to 16 inches. Their fur is sleek and black, and their slender build allows them to squeeze through gaps as small as half an inch. Large, nearly hairless ears, prominent eyes, and a pointed nose distinguish them from the heavier-bodied Norway rat.
Roof rats are nocturnal and excellent climbers, traveling along utility lines, trees, and fences to access rooftops and upper building levels. Once inside, they nest in attics, drop ceilings, and wall voids, staying close to established nesting sites when foraging. They gnaw through wiring, insulation, and packaging—particularly near food storage—and will settle quickly wherever food and shelter are available.
Roof rats can carry and transmit rat-bite fever (RBF), salmonellosis, and leptospirosis through their droppings, urine, and nesting materials, contaminating surfaces and packaged goods. In food-handling and pharmaceutical settings, this risk can lead to failed audits, product recalls, and shutdowns. Their gnawing also creates a secondary risk of electrical faults and structural damage.
Roof rats nest in elevated cavities—attic rafters, ceiling voids, ductwork, and wall spaces are all common harborage sites. They exploit roof vents, pipe gaps, and loading dock openings to gain access, and shelter in overgrown vegetation outside. Unlike Norway rats, they consistently seek height and concealment, making them harder to detect in large commercial buildings.
Seal gaps around roof vents, utility lines, pipe penetrations, and loading docks—roof rats can enter through any opening larger than half an inch. Store food and waste in rodent-proof containers and remove waste regularly. Trim back trees and vegetation that could provide roofline access, and conduct routine inspections of attics and ceiling voids to catch early signs of activity before an infestation establishes.
Roof rats are remarkable climbers and known to be able to scale tight routes like ropes, branches, and power lines. Once they have accessed the upper levels of a building, they look for small openings or weak spots, such as damaged soffit and vents. As well as being able to squeeze through these small openings, roof rats may also be able to exploit weak roof spots by gnawing a way in.
While technically omnivores, roof rats tend to prefer a plant-based diet and will forage for fruit, seeds, nuts, vegetables, and grains. However, due to their natural scavenging habits, roof rats will feed on human food, pet food, and insects or snails.
Roof rats are often driven indoors by cooler weather, which can make roofs, attics, garages, and sheds an attractive option for shelter. Roof rats may also be attracted by the availability of food, or if escaping predatory threats.
Roof rats typically grow up to eight inches in body length, but their tails add another six to eight inches. Therefore, in total, they can reach up to 16 inches long. Despite their size, their slim build helps them squeeze through very small gaps, which is why exclusion is so important.
Look for droppings, gnaw marks, grease trails, scratching sounds, and shredded nesting material. You might also notice signs of food tampering, especially in storerooms, distribution centers, or break areas.
Yes, roof rats can carry harmful diseases and contaminate food. They can spread bacteria and pathogens, putting people and pets at risk. Regulated industries that handle active ingredients and food products are particularly vulnerable. Always contact a professional if you suspect an infestation.