Mark Brown, Wired UK 26 Jan 11;
In a bizarre example of a symbiotic relationship, tiny bats in Borneo have been found using a carnivorous plant as a toilet, feeding the pitcher plant with their droppings, while they safely roost in the plant’s traps.
Ulmar Grafe, an associate professor at the Universiti Brunei Darussalam, was researching the pitcher plant — a giant, carnivorous vine with deep, pitfall cups that are used to trap prey — for a study published in Biology Letters. Grafe wanted to find out how the pitcher managed to find the nitrogen needed to survive in the nutrient-poor peat swamps of Borneo in southeast Asia.
His team found Hardwicke’s woolly bat — a tiny, four gram animal no bigger than a car key — consistently sleeping in the carnivorous plant’s traps during the day. Sometimes alone, sometimes with a partner or with a child. Roosting on top of each other, two or three bats could snugly fit in the pitchers.
But the plant wasn’t getting its nutrients by munching on the tiny bats. In fact, the plant has adapted to stop the winged critters from tumbling down into the bottom of the trap and drowning in the digestive fluid. The vine’s pitchers have a tapered shape and an unusually low amount of fluid, to stop the bats accidentally becoming dinner. That also prevents the monkeys from eating the insects that the plant catches.
Instead, the plants get their nutrients from the bat droppings, absorbing the faeces and urine for nitrogen.
It’s only the second time that researchers have documented a case of a mammal using a carnivorous plant as a natural toilet. In 2009, researchers found tree shrews defecating into another type of plant. But the shrews didn’t seem to use the plant in return, exhibiting a nonchalant poop-and-go attitude.
The bats, however, have a mutualistic link with the plant, choosing its cosy, dry cavity and lack of blood-sucking ectoparasites as a perfect place to roost.
Tiny Borneo bats roost in carnivorous pitcher plants
Elaine Lies Reuters 26 Jan 11;
TOKYO, Jan 26 (Reuters Life!) - Tiny bats, no bigger than a car key, have been discovered roosting in carnivorous pitcher plants in Borneo -- with their droppings a vital nutrient for the plants.
"It's totally unexpected," said Ulmar Grafe, an associate professor at the Universiti Brunei Darussalam who led the study.
"There's a lot of animal-plant mutualisms, but this one is where the animal gives a nutrient to a plant. Usually it's the other way around."
The study, published in Biology Letters, began by looking at how the pitcher plant -- a vine growing up to 6-10 metres (20 ft to 33 ft) long with 25 cm (10 inch) pitchers -- managed to gain the nitrogen it needed in the nutrient-poor peat swamps and heath forest oon the island of Borneo.
Grafe's team was surprised to find that the roughly 4 gramme (0.14 oz) Hardwicke's woolly bat (Kerivoula hardwickii) consistently chose the pitchers to sleep in during the day, despite a wealth of other possible roosts in the nearby forest.
Not only single bats but male and female pairs, and mother-juvenile pairs, can fit inside comfortably. At night, they fly out to hunt insects.
"The pitcher is a very nice roost for them," Grafe said. "It's dry in there and there's no buildup of blood-sucking ectoparasites that often accumulate in other cavities."
Theoretically, there is some danger to the bat should it fall into the digestive fluid at the bottom of the pitcher. But the plant has adaptations to prevent this, including an unusually low amount of fluid and a tapering pitcher.
Instead of getting nitrogen by consuming the bats, the plants get it from their faeces.
"There's no reason why the bat couldn't fly outside. But they probably defecate in there because they usually do that when they roost," Grafe said.
The find is an example of why diversity matters, he added, noting that much of the forest in Borneo is under threat.
"There's so much extinction of animals and reduction of populations and removal that this again highlights how important it is to save every individual, every creature out there."
(Reporting by Elaine Lies; editing by Jonathan Thatcher)
