Nature

The Many Organisms that Inhabit an Elephant’s Footprint

September 2, 2016 | Erica Tennenhouse

Elephants create foot-shaped homes for aquatic life.

When a 10-tonne African bush elephant stomps across the forest floor, deep craters form beneath the animal’s heavy feet. And as these massive footprints gradually fill with groundwater or rain, they turn into homes for numerous tiny aquatic invertebrates, according to a study published in the African Journal of Ecology.

Elephants are considered ecosystem engineers. As study lead author Wolfram Remmers of the University of Koblenz-Landau in Germany explains to The Science Explorer, they “create open spaces in forests, keep riverbanks from overgrowing, are seed dispersers, and drop fertilizing dung.”

During a field course in Kibale National Park, Uganda, Remmers and his co-authors couldn’t help but notice numerous large water-filled footprints. They wondered whether the elephants could be creating unique habitats for other organisms simply by walking around.

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Sifting through the waters of 30 foot-shaped mini ponds, the researchers discovered a lively array of over 60 species, including water beetles and spiders. Tadpoles also made their way into footprints, but favoured the older ones, as did some dragonfly larvae. Accumulation of fallen leaves makes older footprints attractive to certain species, as they provide opportunities to burrow eggs or hide from predators.

These observations “suggest that there is a succession in the species composition of a footprint over time and that these footprints may also play important long-term roles in several aquatic species, such as frogs,” the authors write.

“It was very interesting and a bit surprising for me that these habitats harbor such a high diversity and density of invertebrates and that individual footprints presumably exist for several years and undergo a succession of different states,” Remmers remarks.

He explains that although other pond-like habitats similar to those created by elephant footprints do exist, they are exceedingly rare in Kibale forest, making elephants “the key to survival of many aquatic species.”