Elephants’ footprints leave behind tiny oases for aquatic life


Karl Gruber, New Scientist

Date Published

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That’s one small step for an elephant, but a giant leap for the survival of tiny aquatic animals. In the swamp forests of Kibale National Park, Uganda, every step elephants take can give rise to a footprint-shaped mini-pond, holding up to 200 litres of water and dozens of invertebrate species.

“I was surprised to find out that these footprints were water-filled all year round, and that they harboured such a high diversity,” says Wolfram Remmers at the University of Koblenz in Germany. Surveying 30 such prints over a three-day period in 2014, Remmers and his colleagues found over 60 species, including beetles, spiders and worms – plus tadpoles.

Many smaller species may live there, too – the team’s sampling method meant they only caught things bigger than 2 millimetres.

The footprints probably play an important role in allowing these small life forms to spread, as they form a network of connected ponds.

“We assume that [the animals] do ‘pond-hop’, especially since many of them can fly,” says Remmers. “The elephant footprints act as ‘stepping-stone-habitats’.”

This makes the presence of elephants unexpectedly important for tiny aquatic species.

“If the elephants disappear those habitats would vanish,” says Remmers. “It is likely that some species – such as some dragonflies – would have a very hard time finding suitable breeding habitats.” Some aquatic species might disappear locally, he adds.

The findings help us understand how large herbivores influence their habitat, says Gary Haynes at the University of Nevada, Reno. We already had an inkling of that, because of the way elephants remove trees and create gaps in forests – sometimes even encouraging the formation of grasslands. Their dung is also an important fertiliser.

But evidently they have an impact on the microscopic scale too. “Modern-day elephants and other mega-herbivores shape [their habitats] in ways we are just beginning to fully appreciate,” says Haynes.