Rats and Mice - What are they?

Scampering and scratching sounds in the walls of your home at night, signs of gnawing or chewing, or damaged food packages can mean you have an infestation of mice or rats. Other signs include droppings and urine, burrows or holes in and around foundation walls, or tracks on dusty surfaces. Mice and rats are prolific breeders. Tackle the problem of occasional invaders right away to avoid a severe infestation.

The house mouse has large ears and is light brown to dark grey with a lighter colour on its belly. It is often found in urban areas. The deer mouse is brown or grey with a white belly and feet. The white colour on the underside of the tail is an easy way to spot a deer mouse. It may invade buildings near fields and woodlands in the fall.

A rat is larger than a mouse and can weigh up to 0.5 kilograms (1 pound). The Norway rat and the roof rat look similar, but their habits are different. The Norway rat builds elaborate systems of tunnels and burrows at ground level. It prefers damp areas like crawl spaces or building perimeters. The roof rat is an agile climber and prefers to live in trees, vines and other dense vegetation. It will infest attics, rafters or roofs, and upper stories of buildings.

Knowing the type of pest you have can help you figure out the best approach to controlling them. For example, a rat trap is too large to kill a mouse.


Mice and rats are carriers of disease, and can damage property. The deer mouse is the most common carrier of the deadly Hantavirus.


Prevention is key in controlling rats and mice problems in the home.

Rodent-proof your home

The first line of defence is to get rid of easy entry points. Mice can squeeze through cracks as small as a dime, while rats can enter through a quarter-sized hole. Even the small gaps created by worn thresholds under doors will allow mice access to your home.

  • Use metal weather stripping under doors, and weather strip windows.
  • Patch cracks in foundations.
  • Stuff steel wool around pipes before caulking or plastering.
  • Cover dryer vents, attic vents or soffits with fine mesh metal screening.

Make your home less appealing to rodents

  • Remove cosy nesting sites in unused clutter around the house and garage.
  • Cut tall grass and weeds back from the house.
  • Secure garbage in containers with tight-fitting lids.
  • Raise woodpiles about 30 centimetres (1 foot) off the ground. Place them away from the house.
  • Never place fatty or oily food waste, eggs or milk products in the composter.
  • Use a layer of heavy metal mesh between the soil and the bottom of the composter.
  • Eliminate water sources like leaky taps, sweating pipes and open drains.
  • Keep the kitchen clean and store dry food and dry pet food in metal or glass containers.


There are several types of traps that can be used to control rats and mice. Follow the manufacturer’s directions on how to use a particular trap.

Snap traps and electronic traps are easy to use and very effective if well positioned and set properly. They generally kill rats and mice instantly. Live traps have trap doors that are triggered when rats or mice walk over them. Follow these general guidelines:

  • Most traps without covers should be set at right angles to the wall, with the baited end of the trap closest to the wall. Some traps like electronic traps and covered snap traps should be set with the entrance parallel and flush against the wall. Set one trap per metre (yard) along walls, or 5 to 10 traps per visible mouse hole.
  • Allow a warm-up period of three to four days by baiting the traps but not setting them, so that the rats or mice become comfortable taking the bait.
  • Use baits of strong-smelling, sticky foods like peanut butter, bacon grease mixed with oats, raisins or gumdrops.
  • Reuse the traps – reused traps are more attractive to rats and mice.
  • Move traps to different locations if the bait does not disappear regularly.
  • Reset the traps in two to three weeks to catch maturing rats and mice.
  • Glue traps are also available and can be used with or without bait.

**It is important to check all types of traps daily.

Ultrasonic Devices

Ultrasonic devices give off sound waves or vibrations that rats and mice dislike. Rats and mice may, however, adapt to the devices and return. Therefore, it is recommended that ultrasonic devices be used along with other pest management practices.


Poisoned baits are a common way of controlling rodents. Follow the directions for use closely. Baits or poisons cannot replace rat and mouse-proofing.

Anticoagulant rodenticides inhibit the clotting of blood. These products are sold as liquids or powders to mix with seed, paraffin blocks, bait packages or loose pre-mixed bait. Products available to the general public may contain the active ingredients warfarin, diphacinone, chlorophacinone or bromadiolone. Note : anticoagulants are usually highly toxic.

Non anticoagulant poisons available to the general public may include the active ingredient cellulose from powdered corn cobs. Some anticoagulant and non-anticoagulant rodenticides are sold as commercial class products and must be applied by a certified professional.

Repellents containing thiram have also been found effective in discouraging mice from damaging young trees and ornamentals.

Use caution when near urine and droppings:

  • Wear rubber gloves and a dust mask during cleanup.
  • Dampen droppings and debris with a solution of bleach and water before wiping up.
  • Wear gloves to dispose of dead rats and mice.
  • Double bag the bodies of dead rats and mice in plastic bags and put in a garbage bin with a secure lid.
  • Wash hands and exposed clothing thoroughly after cleanup and separate from other laundry.
  • Never sweep or vacuum dry droppings. The dust that is raised can cause illness.
© Her Majesty the Queen in Right of Canada, represented by
the Minister of Health Canada, 2010
HC Pub: 091068
ISBN: 978-1-100-15304-9
Catalogue Number: H113-1/13-2010E