There are rats in the house. I see telltale scat on the kitchen table and smears along window sills where they have crawled in through the trelliswork. Thankfully, the wiring is intact and there are no nests. They must go. I don’t want to harm them, but am not as spiritually evolved as the keepers [...]

The Sunday Times Sri Lanka

SOS to Pied Piper to root out the rats

Daleena Samara writes on common household pests we encounter in our new series ‘De-bug’

There are rats in the house. I see telltale scat on the kitchen table and smears along window sills where they have crawled in through the trelliswork. Thankfully, the wiring is intact and there are no nests. They must go. I don’t want to harm them, but am not as spiritually evolved as the keepers of the Indian rat temple where some 20,000 rodents get to play god and share food and milk with worshippers.

Rats are hazardous to health. The parasitic fleas they carried in the Middle Ages near exterminated the human race and stigmatized them in perpetuity. Today, that memory and our knowledge of their bad habits and potential to impart other dreaded diseases make us, correctly, wary of their presence.

“Rats are live in filthy conditions, spread disease and damage property,” says Raja Mahendran, expert in agro and domestic pest control and consultant to numerous pest control companies. “If you spot droppings, you may have a problem. In Colombo, the most troublesome rats are the roof rat and the Norway rat. And there are also house mice.”

The big issue with rats are the parasitic fleas, lice and mice they harbour that spread diseases like typhus, jaundice, trichinosis and salmonellosis. They harbour various types of worm infections including intestinal tapeworms. They leave behind a trail of urine and scat or droppings, which are potentially dangerous if the rat is infected, for example with Leptospira bacteria that causes rat fever.

The two rat species, the roof and sewer rat, have you well covered. The blackish roof rat (rattus rattus) takes care of the upper reaches of a house, preferring elevated nesting sites, while the fat, brown, slightly bigger Norwegian rat (rattus norwegicus) zeroes in at ground-level, preferring ground and underground nesting. Rubbish tips and clutter like piles of firewood or household items are ideal hideouts for the Norwegian.

Both live in colonies and have unique food preferences. In general, roof rats like fruits and vegetables while the Norwegian rat likes proteins like grain, nuts, dog food and greasy foods. But when hungry, they go for whatever’s available. Roof rats even eat paper, soap and candle wax. They will rip up your clothes, books and plastic containers. Both rat species tend to forage in groups and return to the same food source.

The presence of scat and smear, the blackish sweat marks they leave along wiring and on window ledges, is characteristic of rat infestation, says Mahendran. Roof rats in particular are skilful climbers, and sewer rats skilful swimmers. However, roof rats need a foothold and cannot climb smooth surfaces and so look for drain pipes, ledges and frames to climb. Open trelliswork on top of windows and doors are points of entry. Ventilation holes are fine if they are high and surrounded by smooth wall.

Because rats have open-rooted incisors, i.e. incisors that grow throughout life, they tend to bite down on just about anything to sharpen and wear them down. Thus rat infestation can also lead to serious structural damage; roof rats gnaw on electrical wiring and other utility cables running through the ceiling while sewer rats gnaw on underground cables and wiring. They also damage doors and windows. They get their teeth into most things.

Rats also leave behind a scent trail of urine. Because of their propensity for spreading disease, precautions have to be taken to clean up after them – surfaces that have come into contact with rodents have to be disinfected and scrubbed clean, and fabrics, paper or any disposable item showing signs of contamination or which were used for cleaning should be burned. Wear gloves when cleaning up after rats.

To rid your home of rats, make them feel unwelcome, says Mahendran. Deny them entry – seal off all entry points. Rats can pass through very small holes. Do the pen test used by pros – if a pen can pass under a door, so can a rat. Importantly, take care of the immediate periphery of your home. Rodents like to hide in tall grass. An untrimmed lawn, overgrown hedge or clutter and discarded food, attract rats and makes them feel comfortable in the environment. So trim grass, hedges and clear up around the house. Cut overhanging branches within three feet of the roof. Once they enter, there should be no food for them, so clean your premises; store food and garbage in containers with tightly fitting lids. Deny rats places to hide or wander about – they generally avoid open spaces, sidle along edges, and get behind something. Regularly clean areas behind furniture.

Try sprinkling deterrents along their route. Chillie powder around a pinewood bed stored in my garage seemed to deter a rat who had begun to gnaw the bed legs. But it didn’t keep the rats away permanently – there’s always fresh scat on the floor in other areas of that room. Rats don’t like spices. Garlic, chillie and pepper repel them. Google for a list of spices that rats dislike including peppermint, turmeric and curry powder.

You can also set up rat-traps or glue pads yourself. Don’t be put off if these fail to catch a rat in the first few days. Rats are neophobic, says Mahendran. This means that they are wary of new objects in the environment and will steer clear of them. This is why traps usually take time to work. It’s only when the rodent is familiar with its presence that it will explore the trap.

But rooting out rats is not as easy as catching a few of them. Rats work in colonies, and seeing one rat doesn’t mean it’s a loner – there are probably a dozen more and some young. They are creatures of habit and tend to return to places where they have foraged successfully. Rat sightings, in addition to the evidence, could indicate serious infestation, and you may have to consider professional intervention.

About 30 years ago, professional rat controllers would saturation bomb residences with rodenticides such as zinc phosphide, says Mahendran. They would use large volumes and expected it to hit somewhere; but for all you know, there may have been just one rat. This overkill approach resulted in collateral damage because the high toxicity affected not just rats but all other creatures in the vicinity, including possibly the householders. But at the time, the consumer was unassuming and anxious to be rid of the pest, and the industry wasn’t any wiser.

Over the past decade, increased awareness of the hazards of such practices has led to a transformation of the pest control industry from exterminator to protector. A strategic approach to rodent control is now in place with an integrated pest management system that harnesses one or a combination of tools, placed strategically and in the right amount, to rid the problem while protecting the environment and its other inhabitants. Rat control professionals should be able to identify the species of rat causing the infestation, their places of congregation, and recommend a precise system of control to be carried out over a period of about a year.

“Rodent control is not a one-off thing. Say there are 10 rats; being neophobic, they may take time to bait. Some dominant ones may take the bait, but others may never take it or they may come later. So unless the bait is continuously placed, you won’t get rid of your problem,” says Mahendran. “Bait or traps have to be placed every fortnight for a year. Also there are baby rats who take three months to grow… they won’t be taking the bait, so if there is no cage or bait laid in three months, then you may think the same rat has returned. Rats also move from this to the next building. Sometimes people don’t see rats and so they think they have got rid of the problem. But after three months there’s a new crop. So it has to be a continuous programme.”

The industry is rapidly progressing into caring mode, with more sensitivity towards moral and ethical considerations, he says. For example, your pest controllers should tell you that although glue traps don’t kill rats, they cause prolonged torturous death. Herbal solutions are being employed and technology harnessed for effective solutions. For example, deterrents and attracters are used to manipulate the movements of rodents away from an area and towards another, while robotic devices are being developed to draw rats out of the house. Herbal sprays that deter rats are being developed for application on and around the perimeter of the house. Not all of these solutions are available here. In Sri Lanka, most pest control service providers operate in either protector or exterminator mode. The integrated method is more caring and sustainable and the need of the day.

Despite these developments, however, rat populations have been growing. In February, the Colombo Municipal Council announced an increase in rats in Colombo and declared March Rat Control Month. The CMC today offers free rodenticide to householders living within municipal precincts. While numbers of the rodent population are unavailable, there have been increases in reports of sightings, rat bites and infections — attributed to rapid development forcing the creatures out of their natural habitats.

Mahendran graduated in entomology and started his career in pest control in Sri Lanka, and later became licensed in agro and domestic pest control in Australia and then France. He has worked globally for two leading multinational manufacturers in the industry and now lives between Sri Lanka and Switzerland. In his first job with a pest control organization in Sri Lanka, he came to know the extent of urban pest infestation in not just households but in hospitality establishments, and outdoors in mines, ships and aircraft.

Rodent control is a community effort, says Mahendran. Most householders, restaurants and hotels tend to react only when there is an explosion of rats. However much householders or restaurants or hotels practise good hygiene, unless the city authorities do their part in not only taking away the garbage and cleaning the streets but actually managing the collected garbage well, rodents will feed and breed and then spread into the city.

I have removed the “Welcome, rat!” mat from my doorstep.

Next week: Woodworm


Advertising Rates

Please contact the advertising office on 011 - 2479521 for the advertising rates.