Rat ‘floods’ are a seasonal threat in rural Bangladesh. But a rodent research programme is starting to stop rats in their tracks. Steven Belmain reports.

The Chittagong Hill Tracts (CHT) in south eastern Bangladesh are among the most beautiful and untouched parts of the world. These foothills of the Himalayas stretch from Mizoram State in India, through the CHT and into Burma. The mountains here are covered in lush tropical jungle, and a large proportion of this forest is comprised of bamboo. Bamboo underpins the livelihoods of hill tribe communities – it is a major source of income through export to the rest of Bangladesh and beyond.

Unlike the majority of plants, most types of bamboo do not flower every year. Some, remarkably, only flower every 50 years or so. The flowering cycle follows a predetermined ‘internal clock’ which means that, when the timer goes off, all the bamboo of that particular species starts to flower. As a result, every so often, entire forests of bamboo in the Bengal Bay Region (India, Bangladesh, Burma) begin to flower at the same time – an ‘event’ which can spread over two years or more.

But this botanical curiosity has darker, consequences – the last major flowering in 1958, for example, led to a large-scale food crisis and famine in Mizoram, India. This, in turn, inflamed underlying unrest and sparked a 20- year civil war against central Indian authority which ultimately led to the creation of Mizoram State in 1987.

Famine and bamboo flowering go together because the flowering sets off a chain reaction leading to ‘rat floods’. Once the process starts, rats living in the forest are suddenly provided with a lavish feast in the form of large and nutritious bamboo seeds. This huge increase in food supply causes a rat population explosion.

But the supply of bamboo seeds eventually runs out, and the rats have to look elsewhere for food. So they leave the forests, eating everything else they can find, causing large-scale devastation to field crops planted by local villagers. This in turn leads to food shortages and regional famine.

At the time of writing this is precisely what is happening in the Chittagong Hill Tracts. The bamboo has begun to flower, there has been a rat flood and local people are short of food. They have been provided with emergency aid, but this does not deal with the underlying problem. Rats.

However, help is at hand in the form of a programme – part of DFID’s Research into Use (RIU) initiative – which aims to develop ecologically-based rodent management (EBRM) strategies. The aim is to produce a sustainable, cost effective means of dealing with rat floods which is easily implemented by farmers and communities.

The Rat Management for Rural Communities project, started in 2008, builds on six years of research activity in Bangladesh. Since 2002, research on rodents – their biology, the damage they cause and prospective management – has been carried out with the help of rural communities in the Comilla region. They work in partnership with organizations which include AID-Comilla, the Bangladesh Rice Research Institute, the Bangladesh Agricultural Research Institute and the Natural Resources Institute of the University of Greenwich in the UK.

This project is not only helping farmers in Bangladesh, it should have worldwide application. Rats are a global problem, affecting rich and poor alike. They eat our crops, contaminate stored food, damage our buildings and possessions, and spread dangerous diseases to people and livestock. And this is most acutely experienced by those least able to manage it – the rural and urban poor.

The reason we need a scientific, evidence-based programme for EBRM is because knowledge about the effect rats have on health and agriculture tends to be anecdotal. Unless we get an accurate understanding of the damage rats cause and how much this costs, it is difficult to convince people to invest in rodent control.

Our monitoring activities in villages showed that rodent damage was common and considerable. Rice growers reported that rats ate up to 17% of the rice in the fields, and, after harvest, each farming household lost upwards of 200 kg of stored rice a year. There was also significant harm (10-50%) to other fruit and vegetable crops. Beyond this, rats damaged house walls, personal possessions, roads and fields. And one in 20 households reported that, in any given month, members of their family had been bitten by rats in their sleep. “We didn’t realise how much the rats ate,” one villager said, “but now we do, since seeing the difference the community-based rat management programme can make.”

But how to solve the rat infestation? Traditional methods of control, such as poisons, rarely work. They are often not used properly, and aren’t adapted to local conditions. At the same time, local awareness and knowledge of alternative means of rodent control is often low. The result is a kind of fatalism – people believe they will just have to put up with the problem.

However, this mindset can be changed when people learn just how much rodent damage is costing them and their families, and when they are equipped with credible, effective tools and strategies for controlling rats. This we see happening in Comilla. 

Our experience points to three essential steps in developing an ecologically based rodent management strategy. The first is to find out what kinds of rats are involved and how they behave. Understanding the nature of the damage rats cause to different crops and human health is important for targeting control measures at the right time and place.

Secondly, we need to understand the impact on those most affected by rats. Developing a locally acceptable strategy means taking into account people’s financial and time constraints, their knowledge levels and cultural attitudes. Would they, for instance, be willing to eat rats? Rats are considered a delicacy in some parts of the world, including some of the different cultures of the Chittagong Hill Tribes. 

Third, we need to evaluate the effectiveness of different rodent control measures in specific local circumstances, and select the most appropriate.

We start by training 25-30 people from each village on basic rodent biology, common technology available to control rats and the principles of EBRM. These ‘trainees’ then spread the word, and we continue to work with them to demonstrate how EBRM works in practice where they live. For example, this involves showing villagers how traps should be placed and set for maximum efficiency, or helping people monitor changes in levels of rat damage. Within two to three months, households throughout the community can see for themselves that EBRM works better than the poisoning campaigns they previously employed. With first hand experience of the effectiveness of the approach, villagers are then ready to carry on with it by themselves.

Our experience is that community level intensive trapping should provide the backbone for any EBRM strategy in rural communities. Although trapping is relatively laborious, traps last a long time, and communities find traps easier and cheaper to use than poisons. Most will catch between 1,000 and 2,000 rats each and can last up to three years or more.

Trapping as a communal activity spreads the cost and also means it operates on a scale big enough to minimise the migration of rats back to the treated area. Rural communities that have tried communal trapping have been very enthusiastic. For the first time in their lives they can see what it is like to live a life free of rats. “Since our village started community-based rat trapping with the new traps, we have more food to eat,” said one villager. “Now that the rats are not eating our stored food, the rice in our food store lasts much longer and doesn’t go down so quickly.”

This form of trapping is phenomenally successful – we have seen reductions in rat numbers and damage of more than 80%. It is environmentally sustainable – it does not use expensive, harmful chemicals. It is cheap – traps can be used again and again. It has proved a major time and money saver – there is less damage to repair. “Before we started the rat management programme, I would spend hours and hours repairing the walls of our house where the rats had made burrows,” said one participant. “Now that there are fewer rats around, there aren’t nearly so many holes in the walls, so I can spend the time doing other things.” And ultimately people are able to grow and store more food, either for their families or for sale.

One of the most rewarding results of this research programme is that once communities see exactly how effective communal trapping can be, they then purchase for themselves the rat traps they have seen in action and carry on their community-level trapping independently. Once these communities have bought-in to the programme, other communities can then be trained on EBRM in the same way. The Rat Management for Rural Communities project is now rolling out this ‘tried and tested’ strategy – spreading the word that rats can be controlled effectively and ecologically.

Dr Steven Belmain is an ecologist and rodent expert based at the Natural Resources Institute, University of Greenwich, UK. 

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