Dealing with rats: here’s what you can do

Rats are dangerous. They spoil food and chew through many materials, including electrical wires that can then cause fires. They are known to spread a large number of human diseases like typhus, salmonellosis, leptospirosis, bubonic plague, or rat-bite fever. Their hairs, droppings, and urine can cause severe allergies. They can also bring fleas, mites, ticks, and lice into your home.

In British Columbia, the most troublesome rats are two introduced species, the Norway rat and the roof rat. The Norway rats, also called brown or sewer rats, are larger than roof rats. They build elaborate systems of tunnels and burrows, and usually remain in the basement or ground level. The roof rats, also known as black rats, are agile climbers and usually found in elevated spaces such as attics, walls, rafters, or roofs, and upper stories of buildings. Both Norway rat and roof rat can occur in the same building.

How can you manage them? Here are some tips.

Identification

• Know which species of rat is present in order to choose the correct control strategies.

Prevention and exclusion

• Rodent proofing. Make sure doors, windows, and screens fit tightly. Seal or cover all openings to your house. Repair damaged vents or cover with fine mesh. No hole larger than 1.2 cm (1/2 inch) should be left unsealed. Roof rats often enter buildings at the roofline, so be sure that all access points in the roof are sealed.

• Housekeeping. Good housekeeping will reduce available shelter and food sources for rats. Stack firewood, pipes, lumber, crates, and other household items off the ground and away from buildings. Secure garbage in containers with tight-fitting lids. Do not compost any animal products, and use only rodent-resistant composters. For roof rats in particular, cut tall grass and vegetation back from the house.

Trapping

• Several types of traps are available for controlling rats. Snap traps and electronic traps are easy to use and very effective if positioned and set properly. Place traps in natural travel ways, so the rats will pass directly over the trigger of the trap. For roof rats, the traps should be placed along beams, rafters, or other travel ways. For Norway rats, traps should be placed under cabinets or next to a wall. Traps may be baited with a variety of food items, such as peanut butter or raw bacon.

• Live traps and glue traps are also available. Live traps are not preferred, because trapped rats must be either humanely killed or released elsewhere. Glue traps are less effective for rats than for mice. Also, the rats caught in glue traps might not die quickly and can struggle for quite some time, often dragging the trap as they try to escape.

Baiting and repelling

• Poisons are not recommended for rat control inside buildings, since poisoned rats can die in hard to reach places causing unpleasant odours. Toxic baits might be needed to achieve adequate control, especially if the rat populations around a building are high and there is a continuous re-infestation from surrounding areas. In this case, consider hiring a licensed pest control operator.

• Ultrasonic devices give off sound waves or vibrations that a rodent dislikes. However, rats may quickly become accustomed to repeated sounds, making the use of such frightening devices ineffective for their control. Similarly, no chemical repellents have been found to deter rats for more than a very short time.

• For current chemical control options, consult your local pest control representative. Follow closely the directions and cautions on the label. Wear gloves to handle dead rats. Double bag the rat carcasses in plastic bags and put in a tightly covered garbage bin.

Rana Sarfraz is an entomologist and ecologist currently working at the University of British Columbia.