The awesome Nepenthes
They are carnivorous, eating anything from ants to mice. Various animals find homes in them and they are remarkable survivors. Nepenthes are amazing plants- yes… plants! They live in some of the poorest soils and are found from northern Australia through to southeast Asia. But the greatest diversity is to be found on the island of Borneo where untold numbers of species can be found.
So what is the purpose of these sadistic devices? Well, they are elaborate traps to catch their prey. It really doesn’t matter what the prey is, so long as it falls in and promptly dies. The ‘pitcher’ is half-filled with a fluid and protected by a lid to stop rainwater filling it up. Death inside one of these would not be pleasant. Around the rim is a waxy lip with downward pointing hairs that create a slippery slope indeed for any animal that goes close enough to the edge. It then falls in. Even flies have great trouble getting out of a Nepenthes trap – usually contributing to the lovely insect ‘soup’ within. Drowning among the bodies of other careless victims is not my idea of a great way to go.
Ants are the normal prey of the several swamp Nepenthes I investigated, and observing the behaviour of the ants around the Nepenthes plants it seems as if the plant may actually secrete a sweet sugary substance as the ants are fascinated by the outside of the pitcher, licking at its surface. All sorts of prey fall in to the pitchers of the various Nepenthes species. A huge variety of insects, spiders and even small mammals such as mice have been said to fall prey to these plants.
However, there have been some remarkable discoveries regarding other things that use these plants as homes and breeding grounds. Midges and other insects often use the liquid in the pitcher as a miniature ‘pond’ to lay eggs in while rainforest crabs may be found happily sitting in the bottom scavenging on the dead material. Recently a species of ant was found to be using the stem of the plant as a home, helping themselves to the prey trapped within the pitchers. Another recent discovery is the incredibly tiny frog Microhyla nepenthicola which seems to live its life and breed within the pitchers, especially Nepenthes ampullaria in western Sarawak. This frog is the smallest so far known from Asia with males reaching a maximum of 16mm from snout to vent.
So are these boarders and thieves welcome? Absolutely. The pitcher does in fact absorb the nutrients from the prey it captures, but this process is sped up greatly by having animals’ bodies doing the hard work, and all the plant really wants is the poo anyway. In the case of the symbiotic ants they also provide a cleaning service.