Being prepared means recognizing a potential threat and understanding how to neutralize it. After surviving the crisis, you will wish to protect your food stores from an enemy that only hunts at night. A large rat population can decimate your entire pantry in just a few days.
The Centers for Disease Control at Atlanta, Georgia, estimates that in 1977 there were 100 million to 175 million rats, mainly Norway rats, in the United States. Currently, no one knows exactly how many rats are in the USA, but population densities of rats per city block in some U.S. cities range from 25 to 150 rats per block.
The population levels for the Norway rat are cyclic, with sudden increases related to the amount of food and shelter available. Under favorable conditions, 4,000 rats were taken on six acres on a Midwestern farm. It is possible for large scale migrations to occur following floods and fires.
The Norway rat is a ground dweller, favoring human habitats, such as sewers, cellars, storm drains, near water, and rubbish heaps. The rat digs burrows that are complete with separate entrances, sleeping rooms, storage rooms, birthing, and nursery rooms, and dead-end tunnels for a last-ditch defense effort.
Some years after the post-World War II surface nuclear tests in the Pacific, scientists collected rats for radioactivity studies. The researchers were amazed to discover that the islands abounded with rats who had survived in large numbers because their burrows gave them protection from the effects of the nuclear explosions.
The “nuclear rats” were more robust, perfectly healthy, and were so well-adapted to their environment that their lifespans were longer than the average of one year. The rats collected were neither mutants nor genetically deformed.
Rats live in male-dominated packs numbering up to 200 individuals, with a dominant male, several subordinate males, and numerous females. The low ranking rats are excluded from the top hierarchy and live in another section of the territory.
When a female comes into heat, she is pursued by several males for four to five days, during which 200 to 500 copulations will occur. Heat cycles are year-round in captivity, and appear to be spring and fall cycles in the wild.
Being polyestrous, females can produce up to 12 litters of a maximum of 22 babies (pinkies) per litter, but the average litter is only 9. The gestation period is 21 to 26 days, with the young leaving the nest after 22 days. The young attain sexual maturity in three months if male, and a few weeks later for females.
During a 1-year period, one pair of rats can produce 800 offspring. If the offspring reproduce an average of 9 babies, the potential is approximately 15,000 rats descending from the original pair. Luckily, the mortality rate and social pressures keep the rat population down, even when food and shelter are adequate.
Rats are a hazard to humans by being disease carriers. Rats are known carriers of bubonic plague, murine typhus, food poisoning, leptospirosis, trichinosis, tularemia, and rat-bite fever. During the great black death of 1347 to 1352 A.D. in Europe, an estimated 25 million people died.
Plague epidemics have occurred as recently as 1926 in New Orleans. The Centers for Disease Control reports an average of 14,000 people in the U.S. each year are victims of rat-bite attacks, some of which have been fatal.
Rats are carnivores, eating fish and meat. They have been known to kill lambs and piglets. Rats are unique in the Animal Kingdom for being generalists, rather than specialists. Rats have the ability to pass on “traditions” of the pack to their offspring, a characteristic which is unknown in any other lower mammalian species.
Accomplishing amazing feats is commonplace to the everyday life of a rat: they can enter through an opening as small as a ½ inch, climb horizontal and vertical wires equally well, climb the inside of vertical pipes 1½ to 4 feet in diameter and scale the outside of pipes and conduits up to 3 inches in diameter.
Rats can jump vertically 36 inches or jump horizontally 48 inches, if on a flat surface. They can drop 50 feet without being killed and also can jump 8 feet horizontally from a 15-foot elevation. Rats can reach up or sideways 18 inches with ease.
Rats weigh about 1 pound as an adult. Their incisor teeth grow an average of 4 to 5 inches per year, hence gnawing is important to keep the teeth worn down. Rats have a keen sense of smell and a well-developed taste. They prefer fresh food over decayed. A sense of touch is well-developed in their whiskers and coat hairs. Although they possess poor vision and are thought to be color blind, rats have a highly developed sense of hearing.
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How do you know you have a rat problem?
The first is the sighting of droppings, which are different from other animals. A Norway rat’s droppings are about a ½ to ¾ inch long and blunt at each end, whereas the Roof rat‘s droppings are smaller, about 1/3 to ½ inch long and pointed at each end.
Runways are always the same, and the rats run them daily. The runways are free of debris, and rats prefer continual contact with a vertical surface such as a wall or a fence along their runway. The runways inside a dwelling become greasy from contact with the rat’s fur. The tracks of a rat can be determined by holding a flashlight at an angle to cause the rear feet tracks of five toes to cast shadows.
Controlling the rat requires control of the total local rat population and not just individuals. Winter is the best time to start a control program because breeding levels are at their lowest, and it will take the rats 12 months to return to previous population levels. The next best times are spring and fall when it takes the rats six months to recover.
The home territory is approximately 100 to 150 feet radius from the burrow. Populations rarely move away from the territory unless forced to by a crisis. The environment for any mammal must have the basic needs satisfied with food, water, shelter, suitable climate, and reasonable protection from enemies.
Foods favored by rats are meat, fish, cereal, and sweets. Rats have an insatiable sweet tooth for sugar, candy, molasses, syrup, raisins, and sweetened fruits.
Water and shelters are readily available in any of the human habitats where rats exist.
Climate is a limiting factor because if it is too cold, rats cannot survive in unheated structures or in the outside.
Protection from enemies is one population limiting factor. Through natural competition, Norway rats have replaced the Roof rat throughout large areas of the U.S. For example, in Virginia, Roof rats are an endangered species.
Among the members of the same species, competition through maintaining the hierarchy by fighting resulting in deaths of the weaker individuals or by forcing the losers to leave the pack. The losers that are forced out suffer a high mortality rate from predators and other rat packs. Increased population levels reduce reproduction and increases the death levels.
Predators are poor and temporary controls. Cats can only kill 25 to 30 rats per year, and dogs are actually worse because their sloppy eating habits encourage rats. Natural predators, such as foxes, snakes, birds, kill only a small number of rats per year, usually the weak individuals, which strengthens the gene pool of the rats.
Effective control requires that the rat’s environment be changed through sanitation. Trash containers of heavy-gauge steel are recommended, but not 55-gallon barrels, the lids of which may fit so loosely, once opened, that they afford access by rats. The container should have a recessed bottom, be watertight, and rust-resistant.
In food storage areas, a 6-inch-wide strip of white paint should be painted on the floor along the walls to help call attention to rat droppings. Bulk storage of food should be a minimum of 18 inches above the floor and be in tightly sealed steel or glass containers.
Compost can attract rats. Rat proof composts by using a heavy-gauge steel composter or convert a steel trash container by punching holes along the sides every 6 inches in evenly spaced rows. The number of tightly sealed trash containers needed, will depend on how much compost you wish to produce annually.
To kill the rats requires that you learn the burrow sites and the runways. Once you have determined how the rats are getting into the area, then you must seal off the access.
Windows and vents can be secured with heavy metal mesh in a sheet-metal frame. Around pipes, fix a metal collar to prevent rats from climbing. Floor drains, fan openings and related means of access can be secured with metal mesh over the opening. Inspect your site, keeping in mind the things rats can achieve easily, such as jumping 3 feet vertically from a flat surface.
Rats are capable of swimming sewer lines and using toilet bowl traps as entrances to homes. Before the killing process can begin, you must determine whether the rats are harboring fleas, mites, ticks, and lice.
These ectoparasites feed on the rats’ blood and may be infected with any disease. When you have eliminated the rats, the ectoparasites may decide to move in with you because you have destroyed their food source. To destroy the ectoparasites on rats, dust the runways and burrow entrances with an insecticide powder, before killing the rats. The rats will carry the powder back to the burrows on their feet and fur, giving you greater killing control beyond normal methods.
Once these precautions are done, the killing procedures can begin. Snap traps placed along runways are effective. Using a board set at an angle along a well or a box to help guide the rats’ natural curiosity to the trap will increase kill ratios. The proper bait is chosen after pre-baiting unset traps with a variety of fresh foods favored by rats.
The pre-baiting helps the rats lose their instinctive fear of anything new and unusual in their territory, and it helps you learn which bait food is preferred. After a couple of days of feeding the rats, their favorite treats set the snap traps. The trigger can be expanded by using a cardboard or screen wire. Do not be concerned about the human smell on the traps because the smell is a daily part of the rats’ environment.
If the runway is over a steel pipe, secure the trap with a chain wrapped around the pipe and tied with a nut and bolt of suitable size. If the runways are in the rafters, nail the trap to the spot where the rat swings onto the rafter after crawling up the beam. This spot will be recognized by the greasy rub mark smear from contact with the rat’s body.
Gassing burrows with cyanide gas, carbon bisulfide, methyl bromide, and carbon dioxide should be best left to certified-trained technicians for the danger involved for a layman outweighs the benefits.
Anticoagulants kill from multiple doses within 3 to 9 days by causing normal blood not to clot, which results in internal bleeding and hemorrhaging. The rats do not realize they are being poisoned and return to feed on the poisoned bait often.
Because rats prefer to carry food back to their burrows, the bait toss packets extend the access to the entire pack. There are reported populations of anticoagulant-resistant Norway rat populations in the U.S., but it is recommended that you use the anticoagulants, then every 6 to 12 months use a one-shot poison. Rats do not have the ability to vomit. One-shot poisons designed for rats, are relatively safe to use around other animals and humans.
For anticoagulants to be effective, you must be liberal in setting out the bait and continue for at least two weeks to ensure as many rats as possible have the opportunity to take the poison. Efficient bait use requires you to remove and replace moldy, wet, caked, or insect-infested bait with fresh. If the bait is undisturbed after several days, move the station to a more promising spot.
Generally, the bait will be eaten well in the first three days, and then consumption tapers off. Place the bait inside sections of pipe or inside wooden boxes with access holes cut into opposite ends. Bait can be put in shallow dishes nailed to the floor and under a board leaned at an angle over the dish set next to a wall.
Avoid inhaling fumes from poisons and avoid skin contact by wearing rubber gloves. The containers and utensils used for mixing the poison with the bait should not be used for any other purpose. Always mix poisons, especially dry ones, in well-ventilated areas. Lock up poisons, the utensils, and the containers to prevent accidental contact when not in use.
Baits recommended are fresh, frozen or canned meats, fish and pet foods, bacon, yellow corn, cracked corn, hulled oats, apples, sweet potatoes, melons, tomatoes, peanut butter, nutmeats, butter, and sweet items. Molasses, vegetable oil, mineral oil, or fish oil can be used to bind bait and dry poisons together.
Mix bait according to instructions because too much poison will give a strong taste, whereas too little will not kill and may cause later bait shyness. Rats prefer fresh food, so only mix enough bait to meet current needs.
Under humid conditions or where there is a need to float bait on water, mix the bait with 1½ pounds of melted paraffin to 2% pounds of bait. Pour the melted paraffin/ bait mixture into a paper milk carton. After the paraffin hardens, peel the paper away. To form floating blocks, put a short wire loop in the paraffin mix as it starts to set. After hardening, remove the block from the mold and tie another wire or a string onto the loop to suspend it in a sewer or float it on the water.
The paraffin bait resists water, mold, mildew, and insects for several weeks, but rats in dryer environments do not accept it readily as bait.
Poisons can be purchased from your local hardware, garden store, or any number of other suppliers. Contact your local public health service or rodent control bureau to find the poison that has been determined to be most effective for your climate and conditions.
Rat carcasses should be buried or burned. Always wear rubber gloves that have cuffs when handling dead rats. If the carcass is inaccessible, for example, behind a wall, drill a small hole in the wall about four inches above the body and spray a mixture of 10 drops of pine oil to a gallon of water into the area. If you cannot find the exact spot, release a couple of blue bottle houseflies into the room, and they will unerringly fly to the spot, attracted by the smell.
Rats can be a positive enemy force unless you prepare and learn to be a successful survivor.