Commuters of the Forest
Elephant roads in Central African rainforests
Forest elephants have uniquely evolved roles in the rainforests of Central Africa. As ecosystem engineers, their diet and behavior contribute to the composition and structure of the forest because they disperse large seeds over long distances. One manifestation of their ecosystem engineering bears striking similarity to a form of human engineering — roads. In the rainforests of the Congo, elephants have created trails that are sometimes even mistaken for man-made.
If you were to venture through forests almost anywhere in the Congo Basin, you might come across these elephant highways, as researchers Hilde Vanleeuwe and Annie Gautier-Hion did in a 1998 study. They found three distinct types of trails, each used for a different purpose: one for long distance travel, another used for foraging, and a third corridor-like trail found close to clearings¹.
The researchers named the first type of trail ‘boulevards’ and found that they cut across several types of forest ecosystem indiscriminately. In Odzala National Park, Congo, boulevards ran from East to West and were up to 21 miles long, linking well liked forest clearings¹. Forest elephants in Odzala park would certainly go to great lengths for access to their favorite clearings! The trails used for foraging were long and winding. These meandered exclusively through low and medium density marantaceae forests (marantaceae is a class of plants related to arrowroot) where a wide variety of elephants’ favorite fruits are found¹. The third type of trails were described as alleys of high traffic near forest clearing entrances¹. Observation of elephants sniffing the air before entering clearings, and of the elephant track patterns led Vanleeuwe and Gautier-Hion to suggest that elephants use these corridors to watch for humans and other predators before entering clearings.
In his 2002 PhD thesis, Stephen Blake also found that Forest elephants of the Congolese Nouabalé-Ndoki National Park create foraging trails and boulevard style paths which he called bai trails². Additionally, elephants in this area create trails that run along rivers. Smaller trails, created by elephants visiting the river, branch off of them. In Noubable-Ndoki park, bai trails turn into foraging or river trails as they continue longer distances. A later study by Blake, coauthored by Clement Inkamba-Nkulu, found that the mineral springs found in forest clearings are resources that elephants factor in when visiting clearings and creating boulevard trails³.
Not only are the trails significant for forest elephant travels, elephant highways are also important for social and intraspecies interactions. These studies found that forest elephants often travel the paths in groups and elephants traveling alone will join up with groups along the trails. The trails also help elephants to find resources when they are unfamiliar with the area³.
In Central African forests, forest elephants create and travel their own highways to eat, interact and acquire resources. Like human highways, these trails are evidence of the complex organization of elephant behavior and life.
¹ Vanleeuwe, Hilde, and Annie Gautier-Hion. “Forest elephant paths and movements at the Odzala National Park, Congo: the role of clearings and Marantaceae forests.” African Journal of Ecology 36, no. 2 (1998): 174–182.
² Blake, Stephen. “The Ecology of Forest Elephant Distribution and its Implications for Conservation, Chapter 4: Forest elephant trail systems.” PhD thesis, University of Edinburgh (2002): 122–151.
³ Blake, Stephen, and Clement Inkamba-Nkulu. “Fruit, minerals, and forest elephant trails: do all roads lead to Rome?.” Biotropica 36, no. 3 (2004): 392–401.
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To conserve the tropical forests of Africa through acoustic monitoring, sound science, and education, focusing on forest elephants