By tracking hundreds of African elephants for 15 years, conservation scientists have determined that the endangered large mammals could roam more than three-fifths of Africa — nearly six times the size of their current habitat — if not for the growing presence of humans, including threats from ivory poachers on the continent.

In a paper published April 1 in Current Biology, researchers made the first analysis of African elephant ranges compared with environmental conditions at the continental scale. They said their results highlight the need to expand protected areas and plan future infrastructure with a goal of coexisting with African elephants.

The two species of African elephants face a rising extinction risk as they lose more habitat and are hunted for their ivory tusks. On March 25, the International Union for Conservation of Nature listed the African bush elephant as endangered and the African forest elephant as critically endangered, with their populations respectively declining by 86% and 60% in the last few decades. They were previously designated as vulnerable in 2008.

Although elephant hunting for ivory has declined from a peak last decade, the expansion of human presence and fragmentation of elephant habitats is leading to more frequent clashes between the groups, said study author Jake Wall, the director of research and conservation at conservation group Mara Elephant Project.

"As human populations grow and expand, they're naturally coming into more contact with wildlife and with elephants, and elephants have a proclivity for crop-raiding and getting themselves into trouble," Wall said. "There's quite a bit of conflict in this part of the world."

To understand how humans and other factors have been affecting elephant populations, Wall and his coauthors analyzed data from 229 African elephants that were tracked between 1998 and 2013 with GPS-enabled collars. The 3.2 million data points were used to map the ranges of the elephants' movements in several biomes across sub-Saharan Africa, and they were compared against the environmental conditions of their surroundings using Google Earth Engine. The analysis spanned variables such as temperature, water sources, percentage of tree cover and human footprints.

By learning what kinds of conditions African elephants lived in, the researchers extrapolated that 62% of Africa was potential elephant habitat. But the large mammals actually lived in only 17% of that hospitable land, almost entirely because of limits imposed by humans, and only 15% falls within currently protected areas.

"What surprised us is when we looked at the annual range sizes, we saw that it was just the human factors that determined how big an elephant's range is over a yearlong period," Wall said.

African elephants approached areas with a large human footprint less often, though it depended on location. Elephants in protected areas also had smaller ranges, possibly because those habitats are relatively undisturbed or because they are constrained by fences.

Previous research has shown how elephants have been changing their behavior to adapt to human pressures, such as becoming more nocturnal in response to poaching. 

The analysis revealed other trends of elephant movement. Savannah elephants had ranges roughly three times larger than forest elephants, which the researchers suggest is because forests are a plentiful biome with nutritious fruits, requiring less travel. Male elephants also had larger ranges than their female counterparts, who move in family units and take fewer risks than solitary males.

The analysis was missing some important factors due to insufficient data, such as the location of fences, seasonal or temporary water sources and humans' tolerance of elephants. Future research will likely focus on refining these initial findings on elephant ranges, Wall said.

African elephants' already declining habitats are at risk of being pressured even further by Africa's growing population, which is projected to balloon from 1.3 billion people to as many as 2.8 billion by 2050. Yet elephants are intelligent and resilient, said Wall — one elephant his team is tracking lives in a small patch of forest during the day and raids crops at night.

Still, the conservation scientist recommends that protected areas are expanded, unused land is opened up to wildlife and upcoming infrastructure is assessed for additional restriction of animal ranges.

Further research is also needed to learn how much space elephants need and how to protect them, according to Wall. Another important component to understand and engage in is how to mollify relationships between people and elephants, through both technology and social reform, he said.

"How do we view ourselves with wildlife? Is it us versus them?" Wall asked. "Or is it that we're living together and that we're sharing and we're not drawing these hard lines in the sand going forward?"

The study, "Human footprint and protected areas shape elephant range across Africa," published April 1 in Current Biology, was authored by Jake Wall, Mara Elephant Project and Colorado State University; George Wittemyer, Colorado State University and Save the Elephants; Brain Klinkenberg and Valerie LeMay, University of British Columbia; Stephen Blake, Wildlife Conservation Society, Max Planck Institute of Animal Behavior, Saint Louis University and Saint Louis Zoo; Samantha Stringberg, Wildlife Conservation Society; Michelle Henley, University of South Africa and Elephants Alive; Fritz Vollrath, Save the Elephants, Oxford University and Mpala Research Centre; Fiona Maisels, Wildlife Conservation Society and University of Stirling; Jelle Ferwerda, University of Twente; and Iain Douglas-Hamilton, Save the Elephants and Oxford University.