Pitcher plants are carnivores that use nectar at the rim of their tube-like structure to attract prey such as insects and small vertebrates. A slippery substance at the rim causes these animals to fall into the digestive juices contained in the plant's equivalent of a stomach.

While you might think it would be prudent for animals to avoid these plants where possible, some bats voluntarily clamber inside them.

Woolly bats are known to roost in Nepenthes hemsleyana, a tropical pitcher plant found in Borneo.

While the bat gets a hidey-hole to rest in, the plant benefits by catching the guano (faeces) that the little mammal produces. This provides the plant with the nutrients it needs to survive.

A similar relationship occurs between tree shrews and another Bornean pitcher plant, Nepenthes lowii. The shrews climb onto the pitcher's rim to feed on the nectar. In return, with the plant's hollow body acting a bit like a toilet bowl, the shrews drop their nutritional faeces into the plant's stomach.