A subspecies of the carnivorous pitcher plant in Borneo has developed a most unusual but mutually beneficial relationship with the Hardwicke's woolly bat, National Geographic News reports. The bat sleeps safely inside the leaves, while the plant thrives on nutrients from the bat's droppings.
"This was a most unexpected and surprising result," scientist T. Ulmar Grafe of the University Brunei Darussalam told National Geographic reporter Christine Dell'Amore. This unusual mutualism apparently is found only in Brunei, a tiny country on the island of Borneo.
The plant's nectar attracts insects, which often fall into the vase-shaped leaves, where a waxy coating keeps them from escaping. The trapped insect is slowly digested by enzymes at the bottom of the pitcher, the National Geographic website said.
The study began, Grafe said, after one of his students discovered a bat inside a pitcher plant while conducting other research. The bat, he reports, "was alive and well, obviously having had a nap within the pitcher until we disturbed it."
The bat obviously received some benefit, but what's in it for the plant?
To find out, researchers captured a number of bats, tagged them with miniature, temporary radio transmitters and tracked their movement to the individual plants where they roosted. The scientists found, National Geographic reports, that plants visited by bats had much more nitrogen in their leaves than control plants that were not used by bats. The study, published in the journal Biology Letters, said bat feces can provide at least a third of the pitcher plant's nutrient needs.
This particular pitcher plant species is found only in trees, where it has a harder time catching insects than plants that grow on the ground, National Geographic notes.
But, Grafe found, the tree-dwelling plant also has bat-friendly pitchers that are up to four times longer than other varieties. These long pitchers, Dell'Amore writes, contain less digestive fluid than other types and also a sort of "girdle" that keeps the bat from sliding down into the fluid.
Both sides seem to enjoy a survival benefit from the deal: in exchange for its safe roost above the girdle, the bat drops nutrient-rich feces down into the plant.