Rodents

Rodents as Pests - The Facts

Norway Rat or Brown Rat (rattus norvegicus)

The Norway rat is large, weighing in at about seven to 18 ounces. It has a blunt snout, small ears, brown fur and the underside is grey to yellowish white in colour. Its body is thick and the tail is shorter than the head and body. It is widespread throughout the UK. These rats live in the sewers and emerge where they find a weakness in the sewer system.

Black Rat or Ship Rat (rattus rattus)

The Black rat is a much smaller sleeker rat, it is capable of climbing quite readily and is usually found at roof level, for this reason,it can sometimes be referred to as the Roof Rat. As the name black rat suggests, this rat is much darker in colour, very dark brown to black. It is a much nimbler creature than the brown rat, it tends to walk on its toes rather than walking on the pads of its feet. If you see the footprints of both rats, you would easily tell the difference. It has a pointed nose, large eyes and large ears.

It prefers to eat fruit and moist foods, it is thankfully quite rare in this country. During my years in pest control, I encountered the black rat once. This was when I worked in a zoo for a pest control company, as a pest control contractor. The zoo had a display of black rats, one day the head keeper came to me and told me that some black rats had escaped from the display enclosure, and he was worried that if not caught, they could cause quite a stir if they started to breed up a population within the grounds of the zoo. There was I, referring back to my text books to refresh my memory on how to deal with black rats.

The difference between the black and brown rat goes much further than physical appearance, their habits are quite different also, the brown rat suffers from neo-phobia, a fear of new things whereas the black rat doesn’t, the brown rat prefers grains and cereals wheras the black rat prefers fruit. The brown rat lives at ground level whereas the black rat lives at roof level. After much studying and thought, I decided upon my plan of action, I asked the head keeper for some fresh fruit, I mixed this with a narcotic type of rodenticide, this meant that the rats could be saved if found after eating the poison, as the antidote for the narcotic rodenticide is just to keep the creature warm until it recovers.

I laid the bait down in the morning, making sure that I had placed it on top of some pipe work in the animal house where the rats had escaped. Just before going home, I thought that I should check that my baits were still in place and had not been disturbed. To my amazement, all of the bait had been eaten, as I was used to dealing with brown rats, I was not expecting the bait to have been touched, as brown rats can sometimes take longer to become accustomed to new things.

I reported back to the head keeper that all of my bait had been eaten, then the hunt for the narcotised rats began. Luckily we found both of the escapees, lying around on top of the pipes, they were both treated sympathetically by the head keeper, and returned to their display unit none the worse for their escapade.

House Mouse (mus domesticus)

The house mouse is small, slender and weighs up to about one ounce. It has a pointed snout, large ears, and its fur is greyish to light brown on top, lighter on the underside. It has a long tail.

Rodent Control

Because of the high risk to humans and other animals, and potential damage to foodstuffs, electrical wiring, insulation, clothing and personal effects rodent control should be taken very seriously in the home or business. Prevention is the better than cure when dealing with rodents.

Diseases carried by rodents

Salmonella

Both rats and mice carry this disease and this can be passed on to humans through food that is contaminated by rodents.

Weills Disease

This disease can be fatal if undetected. It is passed through the urine of infected rats and has flu-like symptoms.

Trichinosis

This disease is transferred to pigs through a minute round worm. From pigs it can then be passed on to man.

Plague

This disease is blamed on the rat flea. Luckily this disease seems to have been eliminated in the UK.

Lyme Disease

This disease is transmitted to man through ticks carried by rats and mice. Symptoms include headache, fever, muscle pain and eventually paralysis.

Treatment for mice and rats

BAITS

There are a number of different types of baits available for both rats and mice, these include grains, pellets and paste baits. Where children and animals are present, tamper resistant bait boxes would be used. For rats we would normally use open trays for bait where there is no risk to children or animals.

CONTACT PREPARATIONS

We have available to us a contact gel. As the name suggests, this kills rodents as they pass through an area that has been treated using contact gel. In order for the gel to kill the rodent it must clean itself through the normal grooming process that all rodents carry out. It is estimated that rodents can spend 25% of their waking time grooming themselves. From this you can see that contact preparations can be very effective if used properly. Use of contact preparations should always be where no children or animals can come into contact with it e.g. behind kitchen plinths or under floorboards. Where there is a risk of contamination of food preparation surfaces then always consider other control methods first.

TRAPS

Old fashioned break back traps and sticky boards are normally used as a last resort against rats and mice. When using sticky boards there are very strict conditions that must be adhered to, and would only be used where other methods have been tried and failed. They can also be used where there is a large population of rats or mice and a quick knock down is required, but they are not used for day to day control measures.

PROOFING

Rodents require an entry point to gain access to your premises. Mice can fit into very small holes and have the ability to flatten their skull to fit through tight gaps. It is said that if you can fit a biro pen into a gap then mice would be able to pass through that gap. Therefore trying to eliminate mice by proofing is not always practical or possible. Rats however require a much larger hole to gain access, and this hole or holes will usually be easily found. Proofing for rats or mice should normally be carried out on completion of your baiting programme. Suitable materials for proofing holes include cement mixed with broken glass, wire wool tightly packed into holes, replacing broken and missing grilles and air bricks, and fitting brush strip to the base of external doors.

When rats or mice use a hole on a regular basis to gain access into your premises, they will leave a smear mark, this is a black mark caused by them passing through the hole and rubbing against the sides of the hole will leave a mark from the grease on their body. This will usually only occur with a heavy or persistent infestation of rats or mice.

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