Identification and Life Cycle
The Norway rat (rattus norvegicus), is also known as the sewer rat, brown rat, and wharf rat. They are common in urban and suburban areas. They burrow and nest under buildings and other structures causing property damage, food contamination, and the transmission of disease.
An adult can be approximately 7 to 9 inches long with brown, gray or black shaggy fur. Its scaly tail is shorter than its body length and can range between 6 to 8 inches long. It has a rounded nose, small ears and eyes.
Norway rat droppings are 1/4 to 3/4 inch in length, and capsule shaped with rounded ends. Depending on its diet, its droppings are usually a shiny black color. The number of droppings may help estimate the size of an infestation.
The roof rat (rattus rattus), is sometimes mistaken for the norway rat, but is not usually found in the Northeast. An adult roof rat is smaller than the norway rat; approximately 6 to 8 inches long with black, gray, or brown smooth fur, large ears, and a pointed nose. Its tail is longer than its body and head combined. They are great jumpers, and usually live high off the ground in trees. In urban areas they can be found on top of buildings, in attics or on roofs.
The average female norway rat produces 4 to 6 litters per year, and may mate again within 1 to 2 days after a litter is born. Breeding is the highest in the spring and fall months, and an average litter can have 8 to 12 pups. They have a life span of up to 1 year.
Habits and Damage
Rats are nocturnal, and will search for food in the early evening or before dawn. If populations are high, you may see activity during the day. They have poor eyesight, and use their acute sense of hearing, smell, taste, and touch to locate food and identify other rats. Rats are suspicious of environmental changes or new foods, therefore it may take a few days for traps and poison baits to be effective.
Rats live in colonies, and prefer to live in underground tunnels, building their nesting burrows often along the outside of foundation walls with chewed paper, cloth or grass. They can live in homes, woodpiles, grocery stores, factories, commercial buildings, restaurants, parks, construction sites, etc. Rats are scavengers, and eat many types of food, but prefer cereal grains, meats, nuts and fish. Unlike mice, rats need water to survive, and will drink from leaky utility pipes, toilets, and sinks.
They gnaw holes in surfaces, and can climb, jump or swim to gain entry into buildings or food containers. Rats can cause damage by chewing on furniture, walls, insulation, plastic, rubber materials, clothing, electrical wires (which can start electrical fires) and wood. Rodents pose health concerns to humans as they can transmit diseases, and trigger asthma.
Common Signs Of Rodent Activity
- Rub Marks. Markings consist of natural oils &dirt from their fur when rubbing against walls.
- Gnawing. Rats will gnaw their way into a structure by enlarging a small opening to gain entry, even through glass and cinderblock.
- Fecal Droppings. Droppings are found along a runway, feeding location or shelter, and can indicate where the rats are most active.
- Burrows. Can be found alongside foundation walls, rubbish or shrubbery, and adjacent to sewer lines.
- Sounds. Listen for squealing and fighting within mating areas.
- Smell. There is often a very particular odor associated with large rodent populations. Once you learn this smell, you will never forget it.
Prevention and Management
The best strategy for rodent control is prevention. An Integrated Pest Management (IPM) program can help eliminate and maintain a rodent-free environment to suit your specific level of infestation.
Inspection. A thorough inspection can determine the nesting and feeding sites as well as identify the interior & exterior problem areas that contribute to the infestation.
Sanitation. Infestations can be greatly decreased by limiting the availability of food and shelter.
Exclusion. Rats can enter buildings through small openings 1/2-inch & larger. Seal small openings to keep them out.
Baiting. Proper placement of bait stations is as crucial as selecting the right bait. Think location, location, location.
Trapping (non-chemical). Can be very effective when done correctly. It is a great method for areas such as homes, schools, and commercial kitchens.
The following steps can be taken to help prevent or reduce a potential problem with rodents.
- Gnaw-proof materials such as copper mesh or steel wool can be used to seal small holes (bait hole first).
- Install door sweepers to insure that doors close tightly. (Rats only need 1/2 -inch space to enter).
- Clean up food waste and spillage daily.
- Screen dumpster drainage holes with hardware cloth.
- Eliminate rubbish piles, and place garbage in industrial dumpsters with tight fitting covers.
- Store wood pallets at least 18-Inches from a structure wall to allow proper inspection.
- Do not leave pet food bowls out overnight.
- Eliminate water sources available to rodents.
- Store food in rodent-proof containers.
- Seal all cracks and openings in the foundation, windows, doorframes, and around utility pipes and wires.