Fighting the Rat Problem Using New Traps, Mozambique

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Introduction

Rats are the most numerous and widespread of all mammals. Nobody knows how many there are in the world, but it probably runs into billions. They live in rural and urban areas, in fields and houses and barns -- anywhere there is food. And they eat almost anything. Even a country as "developed" as Britain recently discovered that it had as many rats as people.

In many parts of the world, they are an everyday menace, eating crops and stores of food, biting people as they sleep and spreading diseases. But many problems could be solved, says the NRI's rat expert Steve Belmain, in the simplest way imaginable -- with a better rat trap.

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Setting the Scene

One region where villagers are seriously troubled by rats in their houses is Zambezia in central Mozambique. The traditional mud houses of this rural region act as both homes and food stores. The inhabitants typically store their maize or rice on a raised platform within their living spaces. This makes sense because the smoke from their fires helps to repel insects that would otherwise eat the grain. But it doesn't deter the rats, which enter the houses in large numbers, especially after harvest when there is no food In the Fields.

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Defining the problem

A typical small hut may be home to eight or nine people, but also up to a hundred rats, living just feet away from their human hosts. A hundred rats will eat about 350 kilograms of grain in a year, which could be as much as half of a typical household's food store. "Rats are a big food security issue," says Steve Belmain.

And they cause diseases. One route is via rat urine and faeces, especially as it falls out of the roof grain stores at night. "Rat waste literally rains down on people while they sleep -- it gets into the water and the food," says Steve. Another route is through bites. Rats running round the house will often bite if they smell food on a sleeping human's hands or face.

The diseases they pass on in bites and urine can cause anything from leptospirosis to rat bite fever and gangrene, says Steve. Rats are perhaps best known for having transported Bubonic plague round the world. Less well known is that Bubonic plague is an annual occurrence in this region of Mozambique.

Many aid and extension workers don't know about the rat problem, says Steve, because they never see them. "Rats only come out at night, when the aid workers have gone. But if you ask villagers, they almost all say that rats are a big issue."

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Taking action

Steve Belmain began looking for a solution to the rat problem in northern Mozambique, in a joint project with the international humanitarian organisation World Vision. "We spent a year, talking to householders and monitoring and setting traps just to find out what was happening," he says. He found that almost everyone had a rat problem, and that traditional solutions -- like buying a cat or setting indigenous designs of traps -- did not seem to work very well.

But he found something else, too. The massive disruption caused by civil wars , which killed much of the region's livestock, coupled with recent flooding, has left people hungry. Malnutrition among children is common. Rat meat may sound unappetising to some, but it is now the most important local source of protein. That, incidentally, ruled out poison as a solution to the rat problem.

"After the research, we decided that if farmers could trap rats intensively enough, we could reduce the rat population inside the house," says Steve. Easier said than done. Rats are very clever. If a rat survives its first experience of a trap, it will keep clear next time. And local traps are not very sensitive. So many rats snatch food and jump clear before they are caught. So Steve has begun importing better, more sensitive rat traps from the US, and hopes to arrange local manufacture.

To test their effectiveness, he has recruited 600 households in three villages to install 10 of these new super-traps in each house. Typical farmers in Morrumbala district caught two or three rats a night. Over five months, the household rat population fell by around 50%. There was more grain in household stores -- and more rat meat, of course. Rats will never be eliminated. But if their numbers can be kept down through intensive trapping, this will reduce disease, cut the loss of grain -- and provide a source of protein.

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The cast

"Rats only come out at night, when the aid workers have gone. But if you ask villagers, they almost all say that rats are a big issue." -- Steve Belmain, NRI

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Global Relevance

Can Steve Belmain's anti-rat formula work in other places? "I believe intensive trapping could work all over Africa, and perhaps more widely" he says. It requires a lot of work, setting and emptying traps each night. And the traps remain expensive as long as they are not produced locally. But where people share their homes with grain stores and rats, it will be worth it. And in many places, there is the added benefit of rat meat.

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Thinking points

• Rats are a hidden problem in many farming communities.
• Poisoning is not a solution if they are eaten by villagers
• Intensive trapping using sensitive traps is working in at least one rat-ridden neighbourhood

Research on new ways of trapping rats in Mozambique was funded by World Vision and the UK Department for International Development's Crop Post-Harvest Research Programme