Mice and rats, the forgotten pests

With a lot of the discussions in the pest control industry focusing on bed bug extermination lately, attention has been removed from animals that can be far more harmful to humans in terms of both health and property damage, those being mice and rats.

Mice and rats have followed humanity around since the earliest days. They found as man progressed, farming, building cozy shelters, and traveling appealed to them. What has happened since the early days in what is now Pakistan and Afghanistan, is that rodents have spread across every continent and in every climate on Earth.

So how do we define the differences between mice and rats?

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 your rat or mouse problem. For example, a mousetrap is too small to kill a rat.

There are six major problems caused by rats and mice:

  1. They eat food and contaminate it with urine and excrement.
  2. They gnaw into materials such as paper, books, wood, or upholstery which they use as nest material. They also gnaw plastic, cinder blocks, soft metals such as lead and aluminum, and wiring which may cause a fire hazard.
  3. Rats occasionally bite people and may kill small animals.
  4. They, or the parasites they carry, (such as fleas, mites, and worms) spread many diseases.
  5. Rats can damage ornamental plants by burrowing among the roots or feeding on new growth or twigs. They also eat some garden vegetables, such as corn and squash.
  6. Rats and mice are socially unacceptable. These rodents have been a problem for centuries, chiefly because they have an incredible ability to survive and are so difficult to eliminate. In addition, they are extremely compatible with human behavior and needs.

What diseases can rodents carry?

Listed below are just some of the diseases that both mice and rats can carry.

Taken from: http://research.ucsb.edu/iacuc/

Lyme Disease
Relapsing Fever
Rat Bite Fever
Rocky Mountain Spotted Fever
Rickettsial Pox
Murine Typhus
Venezuelan Equine
Encephalitis Hantaviruses
LaCrosse Encephalitis
American Trypanosomiasis

How can I manage them?


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.


Options for Control


Several types of traps 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. 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, and 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.


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.

Nonanticoagulant 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 them up.
  • Wear gloves to dispose of dead rats and mice.
  • Double bag the bodies of dead rats and mice in plastic bags and put them 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.
Norway Rat

Norway Rat

House Rat

House Rat