A frog from the Sphaerotheca genus likes the moist environment of elephant dung.
SYDNEY: Some frogs take refuge from the heat by living in the moist droppings of the Asian elephant during Sri Lanka's dry season.
The frogs may be seeking out the piles of droppings because they provide moisture in an otherwise dry environment, which is low on the leaf litter that frogs more typically call home.
The findings, recently reported in the journal Biotropica, also suggest elephants act as 'ecosystem engineers' – animals which modify the physical environment in a way that benefits other creatures. It highlights how important Asian elephants are to the ecosystem, say researchers, though their numbers are in decline.
"Asian elephants are currently endangered and rapidly declining. When we lose them, we lose not only these majestic animals, but also many other organisms" says Ahisma Campos-Arceiz from the National University of Singapore, who first discovered these bizarre species of frogs.
Surprise discovery
Campos-Arceiz was analysing the role of southeast Sri Lankan elephants in seed dispersal when he made his discovery. Breaking open a dung pile near an elephant water hole in search of seeds, he was surprised to find a frog inside.
Campos-Arceiz inspected 290 elephant dung piles, and found a total of six frogs in five piles. The frogs belonged to three species: two types of narrow mouthed frogs, Microhyla ornata and Microhyla rubra, and a frog from the Sphaerotheca genus.
Many of the dung piles also contained beetles, ants, centipedes, millipedes, spiders, crickets, scorpions and termites.
Less known about Asian elephants
African elephants have long been known to have ecological effects on their environments. For example, when the elephants eat, they break off sections of plants, creating rough patches of vegetation which lizards use as shelter.
Much less is known about how Asian elephants interact with their environment, however.
"This is, to my knowledge, the first description of elephant dung as microhabitat for vertebrates … [the frogs] are one of the clearest examples of ecosystem engineering by asian elephants," he said.
The frog-friendly dung was found in an arid environment during the dry season. Campos-Arceiz suspects the frogs take refuge in the dung during the heat of the day, feeding on the small critters in the dung.
The dung forms a mini-ecosystem, he explained: "elephant dung serves as a germination ground for many plants and fungi and as food and shelter for lots of invertebrate and vertebrate animals."
Frogs were not found in any of 180 nearby cow or buffalo dung heaps studied. Campos-Arceiz thinks this may be due to differences in the digestive systems of elephants, cows, and buffalo.
Elephants eat a large volume of food and pass it through their guts very quickly, resulting in food-rich dung. Cows and buffalo, on the other hand, have a four-compartment gut and digest their food thoroughly, resulting in a dense, fine-grained dung with little remaining food value and few insects or other invertebrates.
Scott Keogh, an evolutionary biologist from the Australian National University in Canberra, says the discovery does make sense. "Finding frogs, when the poos are next to water, is no surprise," he said.
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