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All About Rats


Everything you need to know about rats

Rats are a common pest all over the world and even on ships at sea. They often live in gutters and drains, in fields and under buildings and are known to carry serious diseases. Rats were the source of the plague, the black death that killed million of people across Europe in the 17th century. Rats are common in Indonesia and while we learn to live with them it is advisable to keep them out of our houses and away from food, kitchen surfaces and electrical wiring. Here we look at rats and, by understanding them and how they live we can understand how we can control and eradicate them.

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"Tikus Besar"

In 2008 the poor people of Cambodia were struggling as demand pushed the price of rat meat up to around $1.48 a kilogram. At that time Cambodia was supplying around a tonne of rats a day to Vietnam for food. Rats are eaten widely by the Thais and the Philippinos but not by the British army, the British SAS rule book says that rats are the only meat that they are not allowed to eat due to the risk of disease.

Some Rat Facts:

  • Rats are from the genus Rattus in the Murinae family of rodents. There are 56 different species of true rats in the world 31 of which are found in Indonesia.
  • It is estimated that 4 million rats are borne every day around the world, ten for every human being.
  • The most common rats are "Old World" rats, the brown rat (rattus norvegicus) and the black rat (rattus rattus).
  • Pet rats (or fancy rats) are domesticated brown rats and are quite different from their wild relatives, they are smaller, tamer and come in many colours. They do not pose any more risk to humans than other types of pets.
  • The collective noun for rats is a pack or a mischief.
  • Rats reach sexual maturity at 2 to 3 months, they average 4 to 7 litters a year with 8 to 12 pups per litter. Life expectancy is 2 to 5 years.
  • They eat almost anything but prefer food with high protein or carbohydrate content including meats, grains and vegetables.
  • They need a water source such as toilets, sinks, puddles or condensation.
  • They are good swimmers.
  • Rats are crepuscular, they move around most during dawn and dusk.
  • They make nests from soft materials such as chewed paper or grass.
  • People born in the year of the rat are known for creativity, intelligence, honesty, generosity, ambition, a quick temper and wastefulness. They get along well with monkeys, dragons and horses.

Rats live anywhere they can establish themselves that provides a regular supply of food and water, a safe undisturbed place to shelter and nest and a warm environment. They often live both indoors and outdoors near human habitation. They are often found in derelict buildings, in sewers, or wasteland. Here in Indonesia they live in ricefields and, of course, in houses.

They are very shy and scared of humans avoiding contact wherever possible. The most obvious sign you have them is when you hear them running around in the ceiling at night. You may also find them in the house, particularly the kitchen where they can find food, if you turn a light on suddenly. Rather like cockroaches by the time you see one you can bet your life you have several.

Health Risks

Rats pose a health risk to humans and are known to carry 70 diseases (and probably a lot more) including cholera, typhus, lassa fever, hantavirus and leptospirosis. Black rat fleas carry bubonic plague which killed a third of the population of Europe during the 17th century.

Leptospirosis is a potentially fatal rodent borne disease also known as Weils disease. Outbreaks have killed large number of people in Thailand and India. The bacterium is spread through water, moist undergrowth or soil which has been contaminated by rats urine and enters the body through cuts or abrasions.

Rats also carry Salmonella which is passed through food or drink contaminated with rats excreta or urine. Salmonellosis, of course, is a type of food poisoning which results in acute gastro-enteritis, headache, fever and vomiting.

Parasites they carry include ringworm, mites, nematodes, ticks and fleas.

Rats have been known to carry rabies, a serious threat under the prevailing situation in Bali.

But there is another serious threat posed by rats - they like to chew electric cables. Rats are a common cause of electrical short circuits in buildings which can be a nuisance as your power circuits drop out or worse, they can cause fires.

How do I know if I have rats?

1 Look for droppings left around the house. Droppings are black or dark brown, 6 to 12 mms in length and capsule shaped with blunt ends.
2 Look for teethmarks on wood, plastic or food that has been left out. Rat holes may be 5 cms in diameter.
3 Look for burrows in the earth around the house.
4 Switch on lights suddenly at night and see if you detect movement or see one.
5 Sprinkle flour or unscented baby powder on surfaces for them to leave tracks. This will also help you to detect their regular runways.

Pest Control of Rats

Rats are difficult to control, they can burrow, jump and climb and they breed very quickly.

Years ago I met a very experienced local government pest controller. He was the town's expert at catching rats. He said they are clever and learn so you have to get them all at once if you can. When faced with an infestation he would put out many, many traps but not set them. He would bait them and, over a period of time, he would get the rats comfortable with the traps and not suspicious of them. When he was sure they were regularly feeding from them he would set them all to catch the rats all at one go.

Rats are smart. If they find something new to eat they will eat a very small amount and see if they get sick. If they don't get sick they will eat more. This is one of the reasons why rat baits are made as slow acting poisons. Rats get used to eating them and, over time, build up fatal doses.

Rat Baits

In the early 1920's in North America and Canada cattle were dying from internal haemorrhaging. Investigation lead to the source being mouldy silage made from clover leaf. This lead to the development in 1948 of Warfarin which, until recently, was still used as the poison of choice for rats (and of course for the treatment of blood clotting conditions in humans).

Warfarin is an anticoagulant. It is odourless and tasteless and is used as a bait mixed with food. It works by reducing the amount of vitamin K in the blood which is needed for the synthesis of blood clotting substances and it increases the permeability of blood vessels. Warfarin makes the animal bleed to death internally.

Warfarin has the advantage that when poisoned a rat will become dehydrated and will leave the house or building in search of water. No dead smelly bodies in the roof (well not usually).

Rats have progressively developed immunity to Warfarin and this has lead to the development of brodifacoum which is a second generation "superwarfarin". It is far more potent and stays longer in the body. It is highly lethal to animals and birds and extremely lethal to fish.

Rat Traps

There are several types of rat traps available.

The basic trap is a spring loaded device we are all familiar with. When the trap is set, bait is put on the trap. When a rat comes to eat the bait it releases a loop of steel which flips over and breaks the rat's neck. A very quick way to die (well we think it is don't we?). Handle with care, these traps can break your inquisitive toddler's fingers.

Professionals may use a cage type of rat trap which capture the rats alive. Once caught they can be removed and killed humanely often using gas.

A relative new type of trap electrocutes the rat. The rat enters a box, steps onto a steel plate and gets a shock from a charged up capacitor. These traps are battery powered.

Probably the most popular method in Indonesia are cardboard traps with a layer of "Lem Gajah" or elephant glue. The rat steps onto the cardboard and sticks to the glue, the more it struggles the more stuck it becomes. The rat can then be disposed of easily. Incidentally if you wish to release a rat or your inquisitive toddler from a glue trap you can use vegetable oil. I once caught four rats in one night on one elephant glue board.

Steps to protect yourself

1. Keep your house clean, do not leave food out overnight. Pack foodstuffs in plastic or glass containers, not paper. Note that rats can live in refrigerators.

2. Wipe surfaces down, particularly kitchen bench tops and chopping boards that may be contaminated with rat urine.

3. Rodent proofing - close up any gaps around the building that rats can get into, they can get through holes as small as 12mm in diameter. Mice can get through a gap as small as 6 mm

4. Get a cat or a dog. It has been reported that since the rabies outbreak there have been fewer stray dogs around and a resulting increase in the rat population in rice field areas. As has been said repeatedly by the experts we are safer with rabies vaccinated dogs around than no dogs.

5. Make sure electrical cables are properly installed in plastic conduits and junction boxes with no exposed areas. If you find parts of your electrical wiring exposed you have a bad installation vulnerable to rat attack. Not to be confused with the more fatal "Arak Attack".

6. Look under your kitchen sink(s) or washbasins. Very often in this country they do not install U bends or P traps. Instead you may find a flexible plastic pipe. These tend to be very thin and easily nibbled away by rats providing easy access. Rats can come up the sewer, chew through the plastic pipe and get into your kitchen cupboards where, the odds are, they will find a banquet waiting.

Go with the flow. If all your efforts of removal fail perhaps you could consider opening a rat warung. If everyone were to start eating rats the problem would solve itself. As a start here is the original recipe for one of the world's best known dishes:


3/4 pound rat tenderloin
1/8 teaspoon pepper
1 tablespoon olive or vegetable oil
2 cups bell pepper and onion
1 small eggplant cubed
1 medium zucchini cubed
14 oz stewed tomatoes
1/4 cup shredded parmesan cheese

1 Remove the tail and skin the rat. Disembowel it. Chop it into bits. Sprinkle with pepper
2 Heat oil in 12 inch skillet over medium high heat. Cook rat in oil for 3 to 5 minutes stirring occasionally until brown.
3 Stir in the pepper and onion, cook for 2 minutes stirring occasionally. Stir in the eggplant and zucchini, cook for 2 to 4 minutes until the vegetables are tender.
4 Stir in the tomatoes, reduce heat. Cover and simmer for 3 to 5 minutes, stirring occasionally until the sauce is the desired consistency.
5 Serve sprinkling each serving with a drizzle of cheese.

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Copyright © Phil Wilson June 2010
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