Wednesday, February 9, 2011

Unlikely bat roost

As opposed to the carnivorous plant found to be digesting a mouse in a French garden, this pitcher plant (Nepenthes rafflesiana) allows bats to roost in its throat (diagram here) in exchange for the nutrients in the poop they leave behind. The symbiotic relationship between the plant and a type of Hardwicke's woolly bat (Kerivoula hardwickii) was discovered in Brunei on the island of Borneo. "This was a most unexpected and surprising result. We extracted [the bat] and it was alive and well, obviously having had a nap within the pitcher until we disturbed it," remembered study leader T. Ulmar Grafe of University Brunei Darussalam. To track the behavior of the bats, they were caught and outfitted with temporary transmitters. The scientists then compared nitrogen levels and found them much higher in the plants with bats inside them than in unoccupied control plants. The study of 223 pitcher plants found that bat feces can contribute at least 34% of the plant's nutrient needs, according to the study, published in Biology Letters. "There [are] 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 pitcher is a very nice roost for them. It’s dry in there and there’s no buildup of blood-sucking ectoparasites that often accumulate in other cavities.” Although this particular species has pitchers up to 4x longer than other species, it is less effective at catching insects because it contains less digestive fluid and lives in trees. Feces-fed plants are not completely unheard of, noted Dr. Grafe: "Using pitchers as toilets is also known for tree shrews in mountain areas of Borneo."

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