You will hear part of an environmental science lecture about the relationship between fruit bats and a farming community in Africa.
First, you have some time to look at questions 31 to 40.
Now listen carefully and answer questions 31 to 40.
We've been examining conflicts that develop when protected wildlife feeds beyond the boundary of a reserve.
I'd like to illustrate this with research I recently helped to conduct in northern Malawi in villages surrounding the Kalewa bat reserve.
The reserve contains a network of caves and woodland used by 12 species of bat.
Most families in the nearby villages grow fruit and maize on a small scale.
Although bats sometimes feed in their orchards, the animals also provide important ecological and social benefits.
Insect eating species, for instance, consume huge numbers of moths.
The larvae of these moths can cause serious damage to maize before it is harvested, so the bats perform a valuable form of pest control.
Their feeding habits protect people as well as crops.
Mosquitoes are common around irrigation channels and their bites can transmit disease.
By eating these insects after sunset, bats reduce the risk of farm workers being bitten while they are outdoors.
People in the area have long understood these benefits.
Stories and carvings featuring bats have been part of local culture for generations well before the reserve was officially established.
In more recent years, the evening spectacle of thousands of bats leaving the caves has attracted increasing numbers of visitors.
Their spending on guides, food and accommodation now provides useful income for several villages.
Despite their protected status, however, bat numbers have been falling.
Some deaths are accidental.
A small wind farm was built outside the reserve several years ago, and bats can be struck by turbines while they are feeding at night or moving between seasonal roosts.
The blades are difficult for them to detect when they are traveling quickly.
Power infrastructure presents another danger.
Bats occasionally land on high-voltage lines and may touch two live components at once.
Electrocution is most common during storms, when strong gusts make controlled flight difficult and wet fur conducts electricity more readily.
Fruit growers can also threaten the animals.
When a large proportion of a crop is damaged, some farmers set traps, even though this is prohibited.
A few have also been known to poison bats by treating pieces of fruit with agricultural chemicals.
This is illegal and may harm owls and other animals that later eat the dead bats.
So what can farmers do to protect their fruit without injuring wildlife?
One suggestion has been to remove wild fruit trees from the edge of an orchard because these trees appear to attract bats.
Our observations showed that this is actually counterproductive.
The wild trees provide an alternative food supply and without them the bats concentrate more heavily on cultivated fruit.
A more reliable option is to place a net around each orchard tree.
If it is fitted properly, bats cannot reach the fruit.
However, suitable material is costly and the net must be checked frequently so that birds do not become caught in it.
For most small farms, protecting every tree in this way would be too expensive.
Nearly all the farmers therefore spent time trying to frighten bats away without harming them.
Some had tried keeping a dog in the orchard, but this made little difference because the bats remained well above the ground.
A radio was much more useful.
Farmers left one playing beside the trees during the first few hours after sunset and the changing voices and music discouraged bats from settling.
Light provided another temporary deterrent.
During the weeks when the fruit was ripening, family members took turns to shine a light into the branches whenever bats approached.
Simple battery lamps were sufficient, although the beam had to be moved regularly because the bats soon became accustomed to a light that stayed in one position.
No single measure worked all night or in every orchard.
The farmers who lost the least fruit used a combination of methods, for example, a radio on most evenings, moving lights when bat activity increased, and nets on the most valuable trees.
Even then, some damage continued, so our next stage will examine a longer-term solution that benefits both the farmers and the reserve.
