[LUM#15] On the Elephant Trail
What if memory isn't actually the most remarkable trait of elephants? Researchers hypothesize that the migration routes taken by herds each year may be guided by an exceptional sense of smell, allowing them to detect rain from a great distance.
“It’s a scent typical of the ecosystems we find ourselves in. The smell of wet earth after months of drought, suddenly broken by violent thunderstorms. At times like that, the scent is everywhere—very strong!” We are in Southern Africa, on the border between Botswana and Zimbabwe. In Hwange National Park, Simon Chamaillé-Jammes, a researcher at the Center for Functional and Evolutionary Ecology*, has been observing for nearly 20 years—not the rain, but the 40,000 elephants that inhabit this protected area the size of Belgium.
Memory card
40,000 elephants are also drawn by the scent of this rain, which becomes vital when severe drought strikes, forcing the matriarchs and their herds to set out year after year in search of this precious water. A great migration still shrouded in the mystery in which it is rooted: the memory of elephants. In an effort to document this phenomenon, researchers, in collaboration with the Zimbabwe National Parks Authority, have been fitting elephants with GPS collars since 2009 to track them for two or three years (Science Direct – November 2017).
Thanks to this technology, they were able to track the migration routes of these giants for the first time, routes that sometimes follow straight lines for more than 250 kilometers. They also discovered that some groups of elephants did not migrate at all; but above all, they were able to confirm that “matriarchs follow the routes passed down to them by their mothers, while adapting to current conditions when their usual watering holes have dried up, ” thereby likely enriching a memory that can be drawn upon when a new drought strikes.
Migration on a whim
This observation thus confirms the existence of the legendary elephant’s memory, but it does not rule out the possibility of another explanation: that of an elephant’s extraordinary sense of smell, capable of detecting rain from dozens of kilometers away or even farther. “That characteristic smell of wet earth is a cocktail of several molecules, including geosmin, which can be synthesized, ” explains the researcher. “So we conducted experiments on domesticated elephants to see if they could smell and identify this molecule.” And the answer is yes.
To complete the experiment and demonstrate that elephants can use this scent as a guide when moving around, scientists plan to release this molecule into the environment of domesticated elephants to observe their reaction. “Some researchers believe they could follow the scent of rain for more than 100 kilometers,” explains Simon Chamaillé-Jammes. “What we already know for certain is that it’s not just memory or just perception that governs these migrations, but both. The question remains as to how much weight they give to one or the other.”
Elephants Without Borders
Beyond the ecological and scientific value of these observations, another issue is emerging: the conservation and management of these species, which, in order to migrate, do not hesitate to cross the artificial borders of nations. “When an elephant migrates, it will be counted and managed by Zimbabwe, and then a few months later, it will be recorded by Botswana—even though it is the same animal. This shows that conservation simply cannot be approached on a national scale,” explains the ecologist.
To better manage these large elephant populations, a vast transnational conservation area known as KAZA—which includes Hwange National Park—has been established across Botswana, Zimbabwe, Angola, Namibia, and Zambia. The goal? To centralize all data related to these species within a single institution in order to better guide conservation policies, particularly by preserving the ecological corridors connecting protected areas. This is a priority to ensure that the elephants’ ancient migration routes are no longer obstructed.
Toward a Global Atlas of Migration
All over the world, animals migrate. While the Serengeti wildebeest migrations have become famous for the sheer numbers of animals they involve, other migrations have become less visible due to human pressure. “There is a real conservation challenge associated with this phenomenon because infrastructure—roads and fences—is being built along migration routes,” notes Simon Chamaillé-Jammes. In response to this threat, about a hundred researchers, conservation NGOs, and the United Nations Convention on Migratory Species (CMS) launched a project last May to create a comprehensive global atlas of ungulate migrations based on GPS data and local knowledge (Science – May 7, 2021).
Goal: to make this atlas a tool for decision-makers, encouraging them to take migration routes into account when building large-scale infrastructure. “It may be a pipe dream, but these projects are sometimes funded by the World Bank, the IMF, and other major institutions that could potentially use this atlas to make adjustments,” hopes Simon Chamaillé-Jammes.
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