Satellites Reveal How Rare Elephants Survive Desert
for National Geographic News
|September 27, 2002|
Researchers have used satellite tracking to plot an ancient elephant
highway at the southern edge of the Sahara Deserta highly
unusual route that has enabled the elephants to survive on barely
The elephants live in Mali, in the Gourma region of the Sahel, an ever-narrowing strip of land that lies between the desert in the north and the savanna in the south. The Sahel in West Africa is a near-desert wasteland of sparsely vegetated plains and endless miles of sand dunes.
To survive in this extremely harsh landscape, each year the Gourma elephants follow a circular migration path that covers 450 kilometers (280 miles), moving from one water hole to the next. No other group of elephants is known to follow such a pattern. View an interactive map of the elephants' ancient highway, as tracked by radio collars and the satellites.
"The elephants must travel long distances between water holes, sometimes as far as 100 to 150 kilometers (62 to 93 miles) in a day or two," said Iain Douglas-Hamilton, a conservation biologist with Save the Elephants. "They have to move far and fast without water, and they do it mostly at night."
The circular migration route is arduous, with varied terrain and a punishing climate. Many of the water holes dry up quickly after the end of a very short rainy season. An error in judgmentarriving at a spot with no water, for instancecould lead to the death of the herd.
Add growing human populations, decreasing rainfall, creeping desertification, and changing land use patterns, and the survival prospects for the last Sahelian elephants look grim.
As recently as 30 years ago, large herds of elephants ranged throughout West Africa, from the forests along the coastline to the very edge of the Sahara. Poaching, human encroachment, and environmental degradation have drastically reduced their numbers.
Today, elephant populations in West Africa are smallmore than half consist of fewer than 100 individuals. The herds are geographically isolated and their remaining habitat is highly fragmented.
The 325 to 350 elephants in the Gourma region of Mali is one of West Africa's largest populations. Researchers with Save the Elephants, a non-profit research organization conducting elephant studies in Kenya, South Africa, and Congo, as well as Mali, were able to pinpoint the elephant's numbers and migration corridors using GPS technology.
"The whole technology applied to elephants is something we've been pioneering," said Douglas-Hamilton. "It allows us to track the day-to-day movements of individual elephants and actually reconstruct the lives of the elephants in a way that has never been done before."
Led by a matriarch, female elephants and their young travel an average of six miles (ten kilometers) a day, "up and down mountains, in and out of forests, deserts, savannas, across remote places," said Douglas-Hamilton. Bull elephants travel independently and meet up with the rest of the herd around Banzena, the region's most reliable water source, from March to May.
Water holes form the backbone of the migration route; the Sahel has one short rainy season, from late June to late August, and has experienced prolonged periods of drought in the last 40 years.
Amazingly, the elephants seem to be able to hear rainfall from great distances and respond accordingly, said Douglas-Hamilton.
"When the rain falls, they hear it and go within 24 hours, heading for where the rain has fallen. Rain has a very low infrasonic signal and the elephants hear it over great distances," he said.
From Harmony to Discord
In many ways, the Sahelian elephants' survival is due to the exceptional tolerance of the people living in the Sahel, who view the elephants almost as a talisman. Historically, these indigenous groups have been nomadic, moving their cattle, sheep, goats, donkeys, and camels from place to place in search of water and pasture land.
"Both Pheuls and Tuaregs watch the elephants to see when they will move, so they can follow with their livestock to fresh pastures," said Douglas-Hamilton.
As a result, there has been little competition for resources. At some water holes, the nomads water their livestock during the day and the elephants arrive at night to drink.
That harmony is becoming discordant, however, as increasing development of the region has led to an increase in conflicts between humans and elephants.
National and international aid programs aimed at improving the lives of the local people are slowly changing long established land use patterns. By providing permanent water sourceswells or boreholesonce-nomadic people are encouraged to settle into permanent villages, planting crops and grazing their herds in one place year-round.
"It's great to give people permanent water sources, but you have to understand that brings formerly nomadic people into sedentary lifestyles and agriculture," said Stephen Blake, a conservation biologist and elephant specialist with the Wildlife Conservation Society.
Ecological damage caused by agriculture and over-grazing escalates the competition between humans and elephants for ever-dwindling resources. Throughout Africa, in the face of increased human settlement, elephants have been the losers.
Conservationists argue that it's not a question of choosing one or the other, development or conservation. However, development plans need to be carefully designed to take into account the needs of people, elephants, and the extreme fragility of the ecosystem.
"Putting in artificial permanent water supplies on an elephant migration route for the purpose of sustaining agriculture is a sure-fire way to create conflict between the two goals of conservation and development," said Blake.
"Elephants living in great habitat still love eating people's crops. For elephants living in extremely marginal habitat, it's like bees around a honey pot. The locals know this," he said.
"If you want to give people water and make them sedentary," he added, "then put the wells outside of the ecological range of the elephants."
The Mali elephants' tenuous hold on survival is even more troubling given the findings of a separate research team.
Using DNA extracted from the dung of wild elephants in western Africa, biologists at the University of CaliforniaSan Diego, have determined that the elephants are a genetically and geographically distinct species that probably diverged from the forest and savanna elephants of southern Africa a little more than two million years ago.
The San Diego team's findings will be published in the October 7 issue of the journal Proceedings of the Royal Society, Series B.
Wildlife managers estimate that of Africa's 400,000 to 500,000 total elephants, roughly two-thirds are savanna elephants and one-third are forest elephants. Only about 12,000 are West African or desert elephants.
"The elephants of western Africa are far more endangered because of the very limited numbers and the extremely fragmented habitat," said Lori Eggert, a genetics researcher at the Smithsonian Institute's National Museum of Natural History and lead author of the study.
Meanwhile, the Malian government faces the difficult balancing act of improving people's welfare while preserving the resources of the harsh yet ecologically fragile region.
In any program for elephant survival, "people need to realize that African elephants are not interchangeable," said Eggert.
"You couldn't take animals from some of the southern African savanna parks, where the populations are growing too large, and move them to the forest or the desert. The elephants are highly adapted for particular ecosystems."
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