Of Mice, Rats and Men

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Of Mice, Rats and Men
By Lee S. Yudin, Ph.D.
November 28, 1998

Rats and mice are important rodents pests which can enter homes and warehouses for food, water, and shelter. One primary reason why rodents are found in residential and commercial structures is the simple fact that both the rat and mouse eat the same food we as humans eat. If we only had to worry about sharing our food with them they might not be all that serious of a pest. But the fact that rodents also contaminate 10 times as much food as they eat – they become very serious health problem. In addition, rats and mice can carry at least 10 different kinds of diseases to man. On Guam, the three most important rodent pests are the Norway rat, the roof rat, and the house mouse.

Norway rats have a preference for fresh meat, fish and grains, but can survive quite well on an ounce per day of garbage, along with an ounce of water. Norway rats will travel 100 to 150 feet from their ground nests in search of food or water. The Norway rat is reddish – brown with a blunt nose. Its tail is about as long as the combined head and body. The adults weigh between ¾ to1 pound.

Roof rats are climbers and prefer to nest off the ground. Roof rats are especially found in roof spaces, palm trees, and ornamental shrubbery. Roof rats prefer vegetables, fruits and grain, and require an ounce of food and water each day. Their color ranges from black to gray to tan. The tail is longer than the combined head and body. The adults weigh between ½ to ¾ pound.

House mice normally live outdoors in fields and occasionally migrate to structures. In houses, they live behind walls and in cabinets and furniture. They are grain feeders but can nibble on a wide variety of foods, only requiring 1/10 ounce of food and 1/20 ounce of water per day. House mice are brown to gray in color with the tail as long as the body. The adults weight about ½ ounce.

The movement of rats and mice is usually related to food, water, or shelter and will use any method to get to each of them.

Rodent management involves good housekeeping, proper sanitation, rodent proofing, trapping, and baiting. The elimination of food, water, and shelter for rats and mice can greatly reduce their numbers.

Sanitary practices

  • Close or repair dumpsters and garbage containers that are left open or damage
  • Clean food spills
  • Do not allow food to be left out overnight
  • Outdoors, remove food around doghouses
  • In warehouse and food plants, look for spills around loading docks
  • Ensure food in storage is rotated properly (first in, first out) and is stored on pallets, not on the ground or against walls
  • The pallets should be 18-24 inches from side walls and placed so that aisles permit inspection and cleaning around the stored food.

Baiting programs often fail because the bait can’t compete with the rats’ regular food.

Rodent Proofing

Outside of buildings can be rodent proofed by:

  • Sealing cracks and holes in building foundations and exterior walls
  • Block openings around water and sewer pipes, electric lines, air vents, and telephone wires
  • Screen air vents and fit windows and screens tightly

Inside of buildings can be rodent proofed by:

  • Sealing spaces inside hollow block voids or behind wallboard
  • Repairing broken blocks and holes around pipes. Repair gnaw holes or stuff them with copper wool

Trapping, is an underrated method of managing rodents. Traps can be used to eliminate rats and mice where poison baits would be dangerous when human or environment risks are present. Traps can be baited, with food they like to eat, to entice rodents toward the traps. Baited traps should be placed at right angles to rodent runs.

Glue Boards, are better suited for mice and safe for children and pet. Placing a small piece of bait in the center of a glue board can increase effectiveness.

Poison baits, are available as ready to use, premixed baits and are most effective when dealing with large rodent populations. However, when poison baits are used SAFETY must be the first consideration. Poison baits, if used, must be placed where they are inaccessible to children and pets. The risk of accidental poisoning to a child or pet should be taken into consideration before purchasing these types of poisonous baits.

For more information about Rodent control you can contact your local Cooperative Extension Service.