Rat & Mouse (Rodent) Eradication and Control – New Zealand
Rodents include rats and mice. The Pacific Rat or Kiore was introduced to New Zealand by Maori when they first arrived. Mice and the Black Rat and Norwegian Rat were introduced later with European settlement. Rodents found New Zealand very much to their liking and with no significant predators, an ample supply of food for which there was little indigenous competition, the mouse and rat populations rapidly rose and spread. Rats and mice are now pests in all parts of the country and specially in areas associated with man.
There are three species of rat in New Zealand; the Norwegian Rat or Brown Rat (Rattus norvegicus) the Black Rat or Ship Rat (Rattus rattus) and the Kiore or Pacific Rat (Rattus exulans). The Black Rat is the more common candidate for rat control in New Zealand, however, the Norwegian Rat is increasingly common and may come to displace the Black Rat as it has done in other parts of the world.
The head and body of a Norwegian Rat can be up to 30cm long but is normally around 20cm. The tail is usually shorter than the head and body and an adult can weigh up to half a kilogram, It has grey-brown fur and is lighter on the underside. Their droppings are 15-20mm long, usually coloured gray or black. The Norwegian Rat will build nests in any suitable enclosed, safe space but naturally digs burrows into the banks of rivers but it will often nest in the walls and roof voids of homes and other buildings. There are many names often used for the Norwegian Rat, they include, brown, earth, roving, barn, field, migratory, house, sewer, water, wharf, alley, and common rat. All these names are descriptive of the animal’s habits and appearance. Interestingly the name Norwegian was given to the rat by John Berkenhout in Outliles of the Natural History of Great Britain believing that they had arrived on Norwegian lumber ships when it had probably come from Denmark. Since at that time Norway rats had not settled in Norway.
The Black Rat is smaller and more agile than the Norwegian. The tail is usually longer than the body and head. It is a better climber than the Norwegian and often finds its way into buildings via poorly sealed eaves. New Zealand buildings are susceptible to infestation by Black Rats because of gaps under roofing in the eaves. Rats may find their way onto the roof by climbing over-hanging trees. The Black Rat does not build burrows and will nest in trees or in the voids of homes and other buildings making it a prime candidate for rat control in New Zealand.
The Black Death, otherwise known as the plague, ravaged Europe and Asia between the 14th and 17th centuries killing hundreds of millions of people. It was the Black Rat that transported the fleas infected with the bacterium Yersinia pestis. The fleas fed on the blood of the rats and of the people that they came in contact with, spreading the disease as they sucked.
Kiore are rare and now found only in Fiordland, Stewart Island and some offshore islands. They were brought to New Zealand by Maori settlers and have cultural and spiritual importance to Maori. Kiore are not normally a candidate for rat control in New Zealand.
If there is a healthy amount of food available, a female rat will produce up to 12 litters of 20 rats each. One pair of rats has the potential of 15,000 decendents in a year!
Of the mice, the house mouse (Mus musculus) is a pest in urban environments and can be a problem in rural homes, along with species of field mouse, especially in the autumn and winter. Mice are much smaller than rats; typically the head and body is 10cm with a tail longer than the head and body. The fur colour of mice can range from gray to dark brown. Mouse droppings are normally 5mm long, dark brown or black. Many droppings may be found together when there are several mice or if they have been present for some months. Occasionally a trail of greasy marks caused by the continual passage of mice may also be visible. These are caused by the oils from the mouse ’s fur being continually wiped where the mice run regularly. Such trails are a sign of a heavy rodent infestation. Mice continually dribble urine as they run. So any surfaces over which they have traveled will be contaminated.
The numbers of both rats and mice have been steadily rising in New Zealand over the last few years and more and more people are realizing that there is becoming a real need for mouse and rat control in New Zealand.
Rodents will enter your buildings at any time of the year; however, autumn is the time when mice and rats seek new supplies of food, as the natural supplies in the countryside dwindle. They also seek shelter from the colder weather. All too often they easily find shelter and ample food in our homes, offices, shops and factories.
You may hear a scurrying or gnawing sound in your roof space or under the floor as the first indication of infestation. Or perhaps you find a bar of chocolate half eaten in a cupboard. More alarming would be an electrical problem, caused by rodents gnawing though your wiring. With such signs it may be difficult to say whether you have rats or mice. If droppings are found, the identification is much easier. Rat droppings are much larger, typically one inch (25mm) long and with a characteristic pointed end. Mouse droppings are less than 1/4 inch (5mm) long and usually more numerous. A mouse can produce around 80 droppings in a day!