WE ALL like to seem attractive. But if you鈥檙e a tree bearing succulent fruit designed to lure hungry elephants, the resulting attention can be too much of a good thing. The fruit of the marula tree (Sclerocarya birrea) of central and southern Africa evolved to be eaten, and its seeds dispersed by the elephants that travel far and wide in search of it. The female trees, which carry the fruit, pay the price in broken branches, denuded foliage and stripped bark. Sometimes they die as a result.
鈥淓lephants are fond of marula fruit, but the trees pay the price in damage to their bark鈥�
In light of this, you might expect the females to have evolved some kind of defence mechanism, such as denser, tougher wood, to protect them from such affections. Yet a study published last month by researchers at the University of Cape Town, South Africa, has found that the wood of the female marula is no more resistant than that of the male (African Journal of Ecology, vol 45, p 41). The marula鈥檚 survival success must be due to other factors, such as its ability to resprout easily after being damaged.
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Why are elephants so fond of these yellow-skinned, white-fleshed fruit? For much the same reasons humans like them, no doubt. They are succulent and nutritious, with four times as much vitamin C as oranges, weight for weight, and seeds rich in protein. They are very popular with local people, who eat marula-flavoured jam and honey, and drink marula beer and wine. Amarula, a creamy chocolate-tasting liqueur, is drunk worldwide.
It鈥檚 not just the fruit that is valued. Other parts of the marula tree are widely used too, especially in healthcare, albeit as folk remedies that have not been clinically tested: oil extracted from the seed kernels is one of Africa鈥檚 best-known skincare treatments; the bark in powdered form is believed to make a powerful malaria prophylaxis; and people chew the dried leaves to protect against heartburn and indigestion. An infusion made from the inner bark is used against scorpion stings and snake bites, and another made from the fruit is thought to rid livestock of ticks. The bark is also used to make an attractive red-brown dye.
There is inevitably a darker side to this bountiful tree. The huge popularity of marula beer, which is said not to cause hangovers, has been blamed for numerous traffic accidents and an increase in public disorder in several central and southern African countries, especially around this time of year, when the fruit are harvested.
Though marula beer nomally lasts only a few days after being brewed, biochemists at Rhodes University in Grahamstown, South Africa, have been searching for a way to prolong its shelf life. It could then be drunk all year round. The road-safety authorities may well be hoping they don鈥檛 succeed.
