Roof rats, also known as Rattus rattus, are a species of rodent commonly found in urban areas, including Pittsburgh, PA. Unlike Norway rats, which are typically ground dwellers, roof rats are excellent climbers, preferring to nest in high places like attics, rooflines, and trees. Understanding the biology and behavior of roof rats is essential to effective pest control and prevention.

Physical Characteristics of Roof Rats

• Size: Roof rats are smaller and sleeker than their Norway rat counterparts. They typically range from 12 to 16 inches in length, including their tail, which can be as long as their body. Adult roof rats weigh about 5 to 10 ounces.
• Appearance: These rats have slender bodies, pointed noses, large ears, and long, scaly tails. Their fur is usually a smooth, dark brown or black with lighter underbellies.
• Tail: One of the distinguishing features of roof rats is their long tail, which is longer than their head and body combined. This helps them balance while climbing along narrow surfaces like power lines and branches.

Habits and Behavior of Roof Rats

• Climbers: Roof rats are known for their climbing ability, often gaining access to homes and businesses by scaling trees, vines, or power lines. Once they find a way in, they typically nest in attics, ceilings, and upper floors.
• Nocturnal: Roof rats are primarily nocturnal creatures, which means they are most active during the night. This makes it harder to detect an infestation, as they usually come out when people are asleep.
• Nesting: These rodents prefer to build their nests in high places, hence the name “roof rat.” They can create nests in attics, walls, or even upper cabinets in search of warmth and safety.
• Diet: Roof rats are omnivores, meaning they will eat almost anything. However, they tend to favor seeds, fruits, nuts, and grains. In urban environments, they often scavenge from garbage or stored food, creating health hazards.
• Reproduction: Roof rats are prolific breeders, which makes infestations grow rapidly. A female roof rat can have between 4 and 6 litters per year, with each litter producing 5 to 8 pups. This means a small infestation can turn into a major problem in a matter of months if left unchecked.

Signs of a Roof Rat Infestation

Knowing the signs of a roof rat infestation is crucial to catching the problem early. Here are some common indicators:

• Droppings: Roof rat droppings are about ½ inch long, with pointed ends, and often found in attics, behind walls, or near food sources.
• Gnaw Marks: Like all rodents, roof rats constantly gnaw to keep their teeth from overgrowing. Look for chewed electrical wires, wood beams, or plastic pipes.
• Nesting Materials: Roof rats gather soft materials like insulation, paper, and fabric to build nests. If you find these items bundled together in secluded areas, it may indicate a nest.
• Noises: Because they are active at night, you might hear scurrying or scratching sounds in your attic, ceiling, or walls after dark.

How Roof Rats Enter Homes and Businesses

Roof rats can access buildings through tiny openings, cracks, and gaps. Here are some common entry points:

• Rooflines: Gaps in roof tiles, vents, or eaves can provide easy access for roof rats.
• Trees and Vegetation: Overhanging branches or vines can act as a bridge for roof rats to get onto rooftops.
• Utility Lines: Roof rats are skilled at running along utility lines or pipes that lead directly into a home or business.
• Cracks and Gaps: Even a hole as small as a quarter is large enough for a roof rat to squeeze through.