The definition of symbiosis, according to Wikipedia, "is in flux," with the word having been used to describe a broad range of unique interactions between species (famously and most often depicted between sea anemones and clownfish). While some species benefit mutually between such interactions, occasionally symbiosis can entail relationships between living things that are parasitic, as well.
When it comes to the study of myth and folklore, one of the gravest and most terrifying parasitic mainstays from various cultures is that of the vampire. Something about monstrous (and yet manlike) beings that suck the essence of life right out of us has always both intrigued and terrified humankind, as evidenced by ancient interpretations of vampiric beings dating back to ancient Sumerian folklore (and perhaps earlier, though any record of such would be hard to come by).
Vampires are also associated with a number of animals, though none so much as the bat. Hence, it is quite unique that a new discovery has linked the behavior of one species, Hardwicke's woolly bat, to a strange new kind of symbiosis with a carnivorous plant; only the second pairing between carnivorous plants and mammals known to exist.
"The bat roosts and relieves itself in the plant's prey-trapping pitchers, feeding the plant," Discovery News recently reported. The bats do not, however, do so with hope of consuming the insects that gather below in the pitcher fluid. According to Ulmar Grafe, lead author of a study on the creatures in the Royal Society Biology Letters, told Discovery News that "the pitcher tapers too much to allow the bat access," causing the bats to get stuck if they attempt to reach the putrefying insects the plant consumes.
The fascinating part, however, deals with the interrelationship between the two species, and the accommodating nature of the plants themselves. While the plants draw more than 30% of their nutrient from the waste of the bats, they expend little energy producing digestive fluids and attractants intended to bring bugs close by for consumption. Instead, they seem to "focus" on growing leaves and pitchers that provide shelter better suited for the bats, which can fit down into the pitchers, without being able to actually reach the insects below where the pitcher narrows.
Though neither of these creatures is actually a "vampire," we do know that varieties of bats exist that live by leeching blood from their victims. Strange though it may sound, certain species of rare, albino redwood trees are able to live off their "hosts" in the absence of chlorophyll. Discover Magazine's blog featured a piece about the strange, "creepy" plants, describing how they leech energy off of nearby redwoods, since their roots remain attached by virtue of the asexual reproduction this species is capable of. In this way, the albino instances of the plant are able to survive for up to a century, in the absence of chemicals within necessary for photosynthesis.
From the strangely symbiotic, to the verily vampiric, nature never ceases to amaze with it's many wonders.