Rats are social animals and live in colonies with well defined territories that they mark with urine and glandular secretions. The colony has a complex social hierarchy with a dominant male leader and a “pecking order” of subordinate males and ranking females. The strongest and most dominant animals occupy the best nest and resting sites and feed at their leisure. Weaker, subordinate rats are pushed out to less favorable sites or forced out of the territory completely. Rats are aggressive, and social conflicts are most common at feeding sites, prime resting areas, and territorial boundaries. Females fiercely defend their nests and young from other rats.
Rats must be understood to be controlled. Knowledge of their life histories, habitat and food requirements, patterns of behavior, range, and other factors is essential to their management.
Senses of Rats
Rats have poor vision. They are nearly color-blind, and they react to shapes and movement rather than identifying objects by sight. The limit of their vision is 30 to 45 feet. Their eyes are adapted to dim light.
Fear of New Objects (Neophobia)
Rats are wary of anything new that appears in their territory. A bait station, a trap, a block of wood will be avoided for a few days until the rats become familiar with the new object; even then, they approach cautiously. This fear of new objects can make baiting and trapping difficult. Rats will avoid poison bait when it is first placed.
Food and Water
Rats need about 1 ounce of food daily. Norway rats prefer protein-based foods such as meat, fish, insects, pet food, nuts, and grain. Household garbage is ideal food for Norway rats. However, they will feed on non-preferred food if nothing else is available. Rats often cache or hoard food in hidden areas. This food may or may not be eaten when other food supplies run short. Hoarding is important for two reasons. First, rats may be moving toxic bait into a location where the label does not permit it to be. Second, rats may be hoarding poison bait while feeding on their regular food. Thus, a baiting program becomes ineffective. Rats need water every day. The amount varies, depending on the moisture content of their food, but is usually around 1 /2 to 1 fluid ounce. Rats prefer to nest where water is easily available.
Rats give many signs that they are infesting an area. Inspection will determine if a site is infested and will identify where rats are feeding and nesting, their patterns of movement, the size of the population, and the extent of the infestation. This helps the pest control technicians decide what control measures to use, where and how to use them, and how much effort is needed to put the program in place.
An inspection using a powerful flashlight just after dark is the best way to see rats. Dead rats are signs of a current or past infestation. If all that are found are old, dried carcasses and skeletons, it may mean an old infestation. Many fresh carcasses are an indication that someone may be baiting the area currently. If rats are actively observed during the day, the rat population is probably high.
When a building is quiet, squeaks and fighting noises, clawing and scrambling in walls, or gnawing sounds may be heard. ■ Use a stethoscope or electronic listening device to help pinpoint activity.
A single rat may produce 50 droppings daily. Norway rat droppings are 3 /4 inch long. The highest number of droppings will be found in locations where rats rest or feed.
■ Determine if a rat population is active by sweeping up old droppings, then re inspect a week later for new droppings.
■ Look at the appearance of the droppings to determine if rats are currently active. Fresh rat droppings are black or nearly black, they may glisten and look wet, and they have the consistency of putty. After a few days or a week, droppings become dry, hard, and appear dull. After a few weeks, droppings become grey and dusty and crumble easily. Note that old droppings moistened by rain may look like new droppings; however, if crushed, they will crumble and do not feel like soft putty.
Both wet and dry urine stains will glow blue-white under ultraviolet light (blacklight).
■ Use portable ultraviolet lights developed by the food industry to identify rat urine on food items. Other substances besides rat urine also glow, so proper use of this inspection method takes practice.
Oil and dirt rub off of a rat’s coat as it scrambles along. The grease marks build up in frequented runways and become noticeable.
CONTROL AND MANAGEMENT OF RATS in Dubai
Most successful rat control programs use a combination of tools and procedures to knock down the rat population and to keep it down. Methods used combine habitat alteration and pesticide application. Some of the tools, such as baiting and trapping, are lethal to the rat. Some tools are not—rat-proofing, for example. Sometimes applicators recommend changes that their customers need to make, such as increasing the frequency of garbage pickup or making building repairs.
The following sections describe some of the major techniques and tools used in controlling rats:
Food Like all animals, rats need food to survive. Baiting programs often fail because the bait can’t compete with the rats’ regular food. The rats simply ignore the baits or cache them. Reducing the rats’ normal food encourages them to feed on any rodenticide baits placed in their territory.
■ Close or repair dumpsters and garbage containers that are left open or damaged.
■ Clean up food spills.
■ Do not allow food to be left out overnight.
■ Outdoors, remove seeds spilled under bird feeders or food around doghouses.
■ In warehouses and food plants, look for spills around railroad tracks and 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 to 24 inches from side walls and placed so that aisles permit inspection and cleaning around the stored food.
Eliminate Hiding Places
■ Remove plant ground covers such as ivy near buildings.
■ Remove high grass, weeds, woodpiles, and construction debris that permit rats to live and hide adjacent to a building.
■ Reduce clutter in rarely used rooms—basements, storage rooms, equipment rooms.
■ Organize storage areas
In the long term, the most successful form of rat control is to build them out. Also called rat-proofing, this approach makes it impossible for rats to get into a building or an area of a building. Rat-proofing prevents new rats from reinfesting a building once it has been cleared.
■ Seal 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.
■ Caulk and seal doors to ensure a tight fit, especially between door and floor threshold.
■ Fit windows and screens tightly.
■ Caulk and close openings on upper floors and the roof, inspect under siding, and repair damaged soffits.
■ Repair breaks in the foundation below ground level.
■ Seal spaces inside hollow block voids or behind wallboard. Repair broken blocks and holes around pipes.
■ Repair gnaw holes or stuff them with copper wool.
■ Equip floor drains with sturdy metal grates held firmly in place.
Snap Trap. The snap trap is an effective method of killing rats when used correctly. Trapping is advised for use in places where rodenticides are considered too risky or aren’t working well if the odour of dead rats in wall or ceiling voids would be unacceptable, or when there are only a few rats infesting a limited area.
Trapping has several advantages. There is less non-target risk from traps than from a toxicant. The technician knows instantly whether the trap has been successful. Traps also allow for disposal of the carcass so that there are no odour problems.
Another way to trap rats is with glue boards. Glue boards use a sticky material that captures rodents. Although most often used against mice, they are sometimes effective against rats. Be sure to use larger glue boards that have been designed to trap an animal the size of a rat. Be aware that some people consider glue boards inhumane because the rodents are not killed instantly.
■ Place glue boards in the same location as you would place snap traps. Place them lengthwise flush along the wall, box, or other object that edges a runway. Overhead runways along pipes, beams, rafters, and ledges are good sites too.
■ Do not place glue boards directly over food products or food preparation areas.
■ Secure the glue board with a nail or wire so a rat can’t drag it away.
■ Install glue boards in bait stations if people might be upset to observe a struggling rat, where children or pets could come in contact with the glue, or in areas with excessive dust or moisture.
■ Check glue boards frequently and dispose of rodents humanely.
■ Adding a dab of bait to the centre of the glue board may improve its effectiveness.
A rodenticide is a pesticide designed to kill rodents. There are three major formulations of rodenticides used to control rats: food baits, water baits, and tracking powders. Food Baits. Rat baits combine a poison effective against rats with a food bait attractive to rats. At one time, applicators mixed their own baits. Now baits are mostly purchased ready-made and packaged as extruded pellets, in a dry meal, or moulded into paraffin blocks for wet sites. Baits may be obtained in 45-pound bulk tubs, in “place packs” containing less than 1 ounce of bait, or anything in between. Some baits kill rats after a single feeding; some require multiple feedings. Some are anticoagulants (causing rats to bleed to death), some affect respiration, and others have totally different modes of action. Some are only slightly toxic to people or pets, some are moderately toxic, and some are very toxic. Many ancient poisons that are toxic to humans have been used to poison rodents. Experimentation with poisons for killing rodents produced rodenticides made of arsenic, cyanide, strychnine, etc.—stomach poisons that were mixed with food and had such extreme toxicity that they killed any animal that ingested them in sufficient amounts. Rats that did not eat a lethal dose, however, recovered, became “bait-shy,” and communicated their preference—or revulsion—to others in the colony. Because of this, these poisons were undependable. A new type of rodenticide was developed in the 1940s that reduced the clotting ability of the blood. This material, warfarin, became the first anticoagulant rodenticide.
A tamper-proof bait box is designed so that a child or pet cannot get to the bait inside but the rat can. Bait trays and flimsy plastic or cardboard stations are not tamper-proof bait boxes. Tamper-proof boxes vary in type and quality of construction, but they are usually metal or heavy plastic. Rat bait stations are normally larger than those used for mice. Most designs are not considered to be truly tamper-proof unless they can be secured to the floor, wall, or ground.
■ Ensure that bait boxes are clearly labelled with a precautionary statement.
■ Check stations or boxes periodically to make sure that rats are taking the bait and that the bait is fresh. Rats will rarely feed on spoiled bait.
■ Bait boxes should be placed wherever the rats are most active as determined by droppings and other signs (near burrows, along walls, at other travel sites, etc.).
■ Put bait packs in burrows, in wall voids, and similar protected sites. If a site is damp, use paraffin bait blocks or other water-resistant formulations. Put out enough bait and check it often. Incomplete baiting can lead to bait shyness and make control difficult.
■ Be sure to limit the rats’ normal food supply, or your baits may be rejected.
■ Remember that rats fear new objects at first, so your baits may not be taken for a few days or a week.
■ Once bait is taken, leave the box in place for some time. The rats now consider it to be part of their normal surroundings.
■ Good bait placements can be effective even when placed 15 to 50 feet apart. Bait placed outdoors around a commercial building can kill rats that are moving in from nearby areas.
Water baits. Rats drink water daily if they can. When rat water supplies are short, water baits—specially formulated rodenticides that are mixed with water—can be extremely effective. Several types of liquid dispensers are available. The best are custom designed for toxic water baits, but plastic chick-founts can also be used in protected sites. Use water baits only where no other animals or children can get to them.
Tracking Powders. Rats groom themselves by licking their fur. Tracking powder makes use of this behaviour. This formulation is a rodenticide carried on talc or powdery clay that is applied into areas where rats live and travel. The powder sticks to the rats’ feet and fur and is swallowed when the rats groom themselves. The major advantage to tracking powders is that it can kill rats even when food and water are plentiful, or if rats have become bait- or trap-shy. ■ Apply tracking powders more heavily than insecticide dust but never deeper than 1 /8 inch. Best application sites are inside wall voids, around rub marks, along with pipe and conduit runs, and in dry burrows (when permitted by label). Apply with a hand bulb, bellows duster, or with a (properly labelled) flour sifter or salt shaker.
■ Do not use tracking powders in suspended ceilings, around air ventilators, or near food or food preparation areas—the powder can become airborne and drift into non-target areas. The rodenticide in tracking powders is generally 5 to 40 times more concentrated than that in baits. Tracking powders can be made with acute poisons or slower acting poisons.