Rats! (and mice): Kill your Enemy!
Rodent Control
To control rats, implement the following procedures:
Rodentproofing - Rodentproofing is changing the structure of buildings in order to prevent entry of rats and mice. In considering rodentproofing, you must know that
Rats can squeeze through cracks ½ inch wide; mice, ¼ inch wide. Any place a pencil can be poked, a mouse can go.
Rats can climb the inside of vertical pipes 1½ - 4 inches in diameter.
Rats can climb the outside of vertical pipes up to 3 inches in diameter and any size if within 3 inches of a wall.
Rats can jump vertically 36 inches, horizontally 48 inches, and reach horizontally or vertically 15 inches.
Rats can jump 8 feet from a tree to a house if the branch is 15 feet above the roof.
Rodentproofing requires the use of rodent-resistant materials:
Sheet metal (26 gauge or heavier).
Perforated metal (24 gauge or heavier with openings no more than ¼ inch).
Hardware cloth (19 gauge or heavier with openings no more than ¼ inch).
Brick with mortared joints, Cement mortar (1:3 mixture) or Concrete (1:2:4 mixture).
Gnawing Edge-A gnawing edge is the edge of substances which rats can gnaw through (edges of doors, windows, holes where pipes enter buildings, ventilation holes in foundations, roof vents, exhaust fans, and eave vents) and that must be protected with rodent-resistant materials. Searching rodents will find breaks in the rodentproofing so promptly repair any breaks.
Sanitation - Good housekeeping or sanitation is a basic factor in rodent control.
Clean up garbage and rubbish. Properly store garbage (Metal garbage cans should have tight fitting lids).
Properly store food, pick fruits and vegetables when ripe (store foods and refuse indoors in ratproof containers or in ratproof rooms). Remove harborages (remove piles of rubbish, trash). Dry up sources of water.
Predators - Many people have relied on cats and dogs to control rats, but in general cats and dogs are not good tools for control. Food put out for pets is excellent rat food. Most people put out more food than the pet can consume in one day. Rats then clean the bowl overnight. Because pets are well-fed, they are too lazy to hunt. Studies have shown that although predators can keep an area rat free, they can not remove an existing infestation.
Birds of prey, hawks and owls, feed on large numbers of rodents. Barn owls are exceptional rat killers and a pair can be expected to kill several hundred rats over a one year period.
Many species of non-poisonous snakes are very beneficial in rodent control. Do not kill non-poisonous snakes.
Trapping - Trapping is an underrated method of controlling rodents. One reason trapping is often overlooked is that snap traps have been around for a long time and are cheap. Traps can be used to eliminate rats where poison baits would be dangerous, to avoid dead rat odors, and to eliminate bait-shy rats.
It is important to place traps where the rats are. Rats and mice are used to human odors so there is no need to use gloves when handling traps. Since mice travel only 10-30 feet but rats travel 100-150 feet from harborages, more traps are needed to trap mice than rats in a house.
Rats and mice also have different behavior around new objects. Rats are cautious, and it may be a week before they approach a trap. Mice are curious and will normally approach traps the first night. If you don't catch a mouse in the first few nights, the trap is in the wrong location. To help rats overcome trap shyness, place traps unset, in place, for several days. This allows rats to overcome shyness and results in better catches.
Baited traps rely on the rat's being attracted for feeding. The bait must compete with other available foods, so no one bait is ever the best bait for all locations. Rodents living on garbage or spoiled food prefer something fresh. The following are some baits that have proven to be successful:
Whole nuts, peanuts or peanut butter for rats and mice (soak whole peanuts in water overnight; old peanut butter becomes rancid so replace it frequently).
Bacon squares or sardines packed in oil for Norway rats.
Gumdrops , dry rolled oatmeal is excellent for mice.
Small wads of cotton for mice and rats (they look for nest material).
Baited traps should be set a right angles to rat runs or nailed to rafters and beams to take advantage of areas where rats travel. Set traps along walls, behind furniture, and near holes. Remember to set traps where children and pets will not be hurt.
traps - catch rats when they accidentally bump the trigger. Runway traps are available or can be made from snap traps by enlarging the trigger with cardboard, hardware cloth, or screening . There is no bait to go stale, so there is an increased chance of success. In placing runway traps, the trap should be placed at right angles to the wall or along runways. To hold the trap in place on pipes or rafters, use rubber bands, nails, or hose clamps.
Glue boards - Special glue can be placed in pie tins or paper plates. The glues do not harden but will hold a rat in place. Other rats become curious and also get caught. Placing a small piece of bait in the center of a glue board can increase effectiveness. Dusty and wet conditions will impair the trap's effectiveness. Glue boards are better suited for mice and safe for children and pets. Boards may be cleaned with cooking oil.
Poison Baits - When rats are plentiful, poisoned baits are an effective tool to use with trapping. Poison baits are available as parafinized blocks for outdoor use. Water baits are sold as packets of concentrate that are mixed with water. They are administered with a chick fount, available at most feed stores, and are useful in areas where rodent food is abundant but water is in short supply.
There are three types of rodenticides; acute toxins, calcium releasers and anticoagulants. Most acute toxins, like Zinc phosphide, are no longer avilable due to the risk of accidental poisoning. One new acute toxin that is considered safe and effective is bromethalin a mitochondrial poison that shuts down the rodent body's ability to produce energy. Vitamin D3 or cholecalciferol is a calcium releaser that causes too much calcium to be released into the blood, resulting in kidney, liver, or heart failure and it kills anticoagulant-resistant rodents The most common rodenticides are the anticoagulants. The older, multidose anticoagulants include chlorophacinone, coumafuryl, diphacinone, pivalyn, valone, and warfarin. The newer generation of anticoagulants are effective after a single dose and include brodifacoum, bromadiolone, and difethalone. Because the effects show up days after taking the bait, they do not associate their poisoning with the bait. Anti-coagulants are considered safer rodenticides than the acute poisons, because larger doses are necessary to poison humans or pets and these poisons have a simple antidote, Vitamin K1.
Whenever a rodenticide is used, safety must be the first consideration. Poison baits must be placed where they are inaccessible to children, pets, livestock, and wildlife. Where rodent runs are exposed and in all outdoor situations, tamper proof bait boxes must be used. A tamper-proof bait box or station must be inaccessible to a 4 year old child or a dog that can not be opened and the bait can not shaken out. Baits stations should always be placed near where rats live and breed or along travel routes.
About 1 pound of anticoagulant bait should control most rats in and around homes. The baits should be placed in stations with 1/4 pound of bait per station. Shallow containers for holding the bait are best. For added effect, water may be provided separately for the rats to drink.

Referances:
ENY-224, Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: June 1991. Revised: June 2005.
EDIS Website at http://edis.ifas.ufl.edu

Very timely post 230gr: Been having trouble with rats for the past few weeks and have been trying to eliminate them. Bit difficult to do permanently as they come from the bush around us, but at least we can make the house and sheds rat-proof.
Thanks.