Carnivorous plants such as the Venus fly trap are well known for how they receive their nutrition – in fact the clue is in the name. However, the word ‘carnivorous’ is a little misleading as the majority of these specialised plants are actually insectivores - meaning that they predominately eat insects. Of course, no-one should forget the fearsome reputation of the pitcher plants, the only group capable of trapping warm-blooded prey!
Pitcher plants - the largest and perhaps the most impressive of all the carnivorous plants – have a specialised, prey-trapping mechanism which features a deep, bulbous cavity filled with a digestive fluid. The whole device is so effective that not only can they trap small insects, but also larger prey such as cockroaches, centipedes and scorpions. As mentioned before, some of the giant varieties of pitcher plant such as Nepenthes rajah, Nepenthes rafflesiana and Nepenthes attenboroughii are even able to catch prey the size of a large rat – but is that really what they are designed for?
A research team led by Dr Charles Clarke - an expert on carnivorous plants from Monash University in Malaysia has made a study by on the Giant Montane pitcher plant of Borneo - Nepenthes rajah. They have suggested an altogether different food source for this fascinating plant group and in the case of Nepenthes rajah, it looks as though it could it could be animal poo!
Dr. Clarke had this to say on his findings:
"…this species has always been famous for its ability to trap rodents, but I've been looking at the pitchers of this species on and off since 1987, and I've never seen a trapped rat inside. This made me wonder - if it is large enough to trap rats, but it only traps them very rarely, it is likely that the pitchers are large because of some other reason?"
Dr Clarke and his colleagues soon turned their attention to tree shrews after noticing that they sometimes left faeces in the traps of the larger pitchers.
‘…all of a sudden we realised that there may be some relationship between big pitchers and tree shrews. So we decided to look at the pitcher geometry. What we found totally blew us away. In order for the tree shrews to reach the exudates, they must climb onto the pitchers and orient themselves in such a way that their backsides are located over the pitcher mouths. The tree shrews then appear to defecate as a way of marking their feeding territory. That suggests these supposedly ‘meat-eating’ plants have evolved a mutualistic relationship with tree shrews…’
Dr Clark believes that there is still much to learn about the true habits of carnivorous plants. In fact his team suspects that another highland species, Nepenthes ephippiata, is likely to feed on faeces too, as may the recently discovered Nepenthes attenboroughii.…15
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