SIGNING OFF
david & goliath In some conservation quarters, elephants are seen as a destructive force in Africa’s bush; it takes them no time to tear apart age-old trees in the search for food. But perhaps, suggests John Hanks, we can enlist the help of tiny ants to implement a win-win solution: protecting prime stands of vegetation without causing harm to everyone’s favourite animal.
Tim Jackson
best places in Africa to get outstanding sightings of the great animals. But this has come at a price: the riverine forest has been all but destroyed by browsing elephants. So what can be done to prevent the demise of the area’s few remaining trees? A recent study in Kenya may provide the answer. Demonstrating that some trees have natural protection from damage caused by elephants, it came about when Todd Palmer and Jacob Goheen from the Mpala Research Centre at Nanyuki noticed that the pachyderms rarely feed on whistling thorn trees Acacia drepanolobium. These acacias, it seems, have ‘guardian ants’ that swarm aggressively onto anything that touches their home – and elephants are no excep-
Trial and error. A young elephant gingerly attempts to feed on a whistling thorn tree, running the risk of finding itself with a trunkful of ants.
trees from animals that are about a billion times more massive.’ To ascertain whether the ants were indeed the protective factor, Goheen and Palmer offered elephants at a wildlife orphanage whistling thorn acacias with and without ants on their branches. The trees without ants were eagerly devoured. Other browsers are undeterred by the ants; giraffes, for example, have N MY FIRST VISIT TO THE CHOBE short snouts and simply wipe the annoying litRiver in northern Botswana in 1965 tle creatures away with their long tongues. I remember sitting quietly in a mag‘An elephant’s trunk is a truly remarkable nificent area of riverine forest that was alive organ,’ Palmer observes. with insects and birds feeding on ‘But it also appears to be an the maroon, trumpet-shaped flowers these acacias, it seems, have ‘guardian ants’ that of a sausage tree. Five bushbuck swarm aggressively onto anything that touches their Achilles’ heel when it comes to squaring off with a colony of stood below the tree, devouring the home – and elephants are no exception angry ants.’ blooms as they fell to the ground. And this is where the potenThree years later that river frontage tial for protecting Chobe’s trees lies. Since tion. Almost as soon as the herbivores begin to the west of Kasane became part of the it appears that smell alerts the elephants to to feed, columns of angered ants crawl up newly designated Chobe National Park. It was trees that are occupied by ants, the relevant inside their trunks. a move widely welcomed by conservationists ant odours could be extracted and sprayed The ants protect the tree in exchange for at the time, aimed as it was at ensuring the on trees not naturally colonised by the being housed in its bulbous hollow thorns long-term protection of riverine vegetation in invertebrates. Taking the application a stage and for the sugary nectar that is secreted the region, which was under threat even then further, it could become a means to reduce at the base of its leaves. ‘It’s a David and from human settlements expanding along human–elephant conflict associated with Goliath story, where these little ants are up the banks of perennial waterways. crop raiding, in much the same way that chilagainst these huge herbivores, protecting None of us could have imagined what the lies are already used. trees and having a major impact on the ecoarea would look like today. Having enjoyed a It seems that we should never stop looking systems in which they live,’ explains Palmer. high level of protection, Botswana’s elephant to Africa’s extraordinary biodiversity for natu‘Swarming groups of ants, which weigh about population has grown to more than 150 000, AG ral solutions to conservation problems. five milligrams each, can and do protect and Chobe is widely regarded as one of the
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