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Clever Kenyan elephants learn to use rail underpasses

It took elephants in Kenya’s Tsavo Conservation Area just three months to learn where to find underpasses built beneath a controversial new railway line that splits their territory in two, a new study shows.

“This fast learning is indicative of elephants’ high intelligence,” wrote the authors of the study, published in the African Journal of Ecology.

Led by members of conservation NGO Save the Elephants, the research team fitted satellite collars on ten elephants (five males and five females) living in Tsavo Conservation Area (TCA) and tracked their movements from 2016-2019.

More than 176,000 GPS fixes were obtained to support the study, which showed that the elephants mostly crossed the railway and adjacent highway at night. The elephants, especially females with young, significantly increased their speeds when they did so: a sign they felt the crossing points to be risky.

Vital corridor

“Only around 70 percent of the animals that we collared were actually utilizing the underpasses,” said Benson Okita-Ouma, lead author of the study.

He told RFI that if the remaining 30 percent of the study sample that did not use the underpasses was representative of the TCA’s 12,000-13,000-strong elephant population, it would mean a significant number of them shy away from the structures designed to help their movement.

Work on the railway, which links the port city of Mombasa to the capital Nairobi, began in 2014. It extends for 133 kilometres through the middle of the TCA, cutting off a vital corridor for wildlife between Tsavo East and Tsavo West National Parks.

The railway is raised on an embankment and fenced on both sides. This means the only way elephants can get from one side to the other is via the underpasses. There are six of them, each measuring 70 metres long and six metres high, and nine bridges that animals can walk under.

But 90 percent of the original wildlife corridor has now been closed by the railway line.

Oils spills and erosion

Okita-Ouma said connecting different parts of Tsavo is vital. Elephants have vast home ranges and move long distances depending on the season and the availability of food and water in them, he said.

“If you block them in, you are interfering with not just the ecological systems but even the animals themselves in terms of their genetic exchanges.”

Use of the underpasses by other wildlife has also been mixed, preliminary observations have shown. Animals like zebras, buffalo and lions have used them, but giraffes, hyenas and hippos have not.

“This is just the beginning,” said Okita-Ouma. “There is so much going on because of these barriers that we have probably not quantified yet.”

Researchers say the railway project, one of the biggest in Kenya’s history, has not just affected Tsavo. A study published in June in the journal Plos One found that the project’s first two phases (from Mombasa to the town of Narok west of Nairobi) caused environmental damage to fragile ecosystems through erosion, river siltation and oil spills.

Threat to wildlife

Lead author of that study was Tobias Nyumba, a post doctoral research fellow at the University of Nairobi’s Institute for Climate Change and Adaptation.

“A higher percentage of new road and railway construction in Kenya occurs in landscapes that are exceptionally high in biodiversity,” Nyumba told RFI.

“This undoubtedly becomes a threat to the existence of wildlife in their natural environment,” he said, adding that nature-based tourism is a key pillar of the Kenyan government’s development agenda between now and 2030.

“Infrastructure development should not be allowed to occur at the expense of wildlife and nature that the tourists travel to enjoy,” he said.

Okita-Ouma said his team hopes the study of the underpasses in Tsavo will help improve the way government agencies and developers take into account the need for movement of wildlife when they build infrastructure like railways and roads in the future.