Rat (Rattus Rattus and Rattus Norvegicus)

Where usually found

There are two main types of common rat Rattus Rattus the ships rat or black rat and the Rattus Norvegicus brown, Norway or sewer rat. Both vary in colour, from light brown to black, but the ship rat is probably more widespread in New Zealand than the Norway rat, which likes to live near water or sewers. Norway rats are heavier and more aggressive and tolerant of cold.

What they do

Rats eat stored food, kill poultry, damage electrical wires, woodwork, and spread a number of diseases including gastroenteritis, typhus, bubonic plague, rabies, and a form of jaundice. In addition, rats carry fleas. It has been said that more people have been killed with rat borne diseases in the last one thousand years than have been killed in all the wars in that time.

How to control (by natural methods)

Store food in rat-proof containers. Access to under floor areas and other likely breeding places should be made as difficult as possible by sealing holes and defects in skirting boards and other entry points. It is wise to have kitchen floors of concrete. Drainpipes, vent holes and other entrances to sewers should have close fitting metal covers or grids. Refuse and garbage should not be allowed allowed to accumulate and should be temporarily stored in containers with tight fitting lids. Where dogs or other animals are left in outhouses, similar precautions should be taken.

(By artificial methods)

Rats may be killed by poisoned baits. Commercially available poison baits may be set down in the places the rats are known to frequent. Storm, Talon, and Ditrac baits prevents blood from clotting and weakens the blood vessels. Poisoned animals die from internal hemorrhage in one to two weeks after feeding on the bait. Other animals, children or even adults may pick up a bait, and strict precautions should be taken to avoid this. Bait should be laid in tamper resistant, lockable bait stations to avoid consumption of the bait by other than mice or rats. Rats may also be destroyed with fumigation by calcium cyanide gas, but this is a job for the professional, and other animals (including some beneficial ones) may be killed by the treatment.

Life history and other comments

Rats live together in groups, eat almost anything, and are active mainly at night. Their teeth are specialised for gnawing and chewing, two separate processes. For gnawing holes and other destructive activities, the material is removed by the long curved front (incisor) teeth and temporarily stored in the cheeks, where there is a gap in the row of teeth especially suited for this. Every so often, the gnawed material can be  spat out, or passed to the rear chewing teeth if it is to be eaten. The life span can be up to four years, with the number of young being five to eight, and the gestation period less than a month. Rats mature at eleven to twelve weeks, so a single pair of rats have the potential to produce a large number of offspring, especially as mating may occur throughout the year. Theoretically, one female can produce about fifty young a year, most of which will themselves be breeding at the end of the year. In practice over 90 per cent of the babies die before they reproduce. In schools, universities and research organisations, an albino strain of the ship rat is used for teaching and scientific experiments. These domesticated rats are bred in especially clean conditions and are unlikely to carry disease unless they come into contact with a local population of wild rats. The albino strain has pink eyes.

Where to obtain professional advice

CHRISTCHURCH PEST CONTROL LTD

Melvyn or Kevin Gilbert. Phone. (03) 3841636 (NEW ZEALAND)