"To know them is to love them!” said the descriptive sign, hopefully. It was talking about leeches, so I think they’re being optimistic. No resident of Borneo’s Danum Valley seems to instil quite as much horror as these harmless animals – but they fascinate me.
Leeches are so basic, yet perfectly adapted to their lifestyle, which consists entirely of finding and then enjoying a huge meal, followed by a few months relaxation while they digest it. They’re remarkably strong – just try dislodging one from its leaf, or your hand – yet sensitive to body heat and the slightest vibration. A leech’s love life is as simple as its diet. Some hermaphrodite smooching results in a sort of bracelet of eggs, which it then slips off like a pullover. There’s the next generation taken care of.
Yes, they’re neat animals. And their ability to find a host and tuck into their meal unnoticed is quite spooky. There are at least nine species of leech in Borneo, but you’re most likely to come across two. The smaller brown ones inject an anaesthetic as well as an anticoagulant, while the big stripy tiger leeches don’t bother with the anaesthetic.
Most tourists are too busy looking for orangutans and hornbills to notice the prick of a bite; the first they know is a spreading patch of blood on socks or clothing. You’d soon notice a bite from the Kinabalu giant red leech, which can reach more than 30cm long... but fortunately it’s thought to feed on fellow invertebrates, rather than passing travellers!
The rest of the group thought my fascination with invertebrates decidedly weird. We were in Sabah to look at apes and monkeys but my eyes were forever straying to the ground or scanning tree trunks for endearing creepy-crawlies.
And how richly rewarding this rainforest was. Take the millipedes. There were pill millipedes that rolled up into spheres the size, hardness and complexity of a golf-ball; there was a giant millipede that trundled across a fallen tree trunk like a well-armoured train; and there were two amorous flat-backed millipedes that reminded me of a double-decker bus.
The world of invertebrates is full of surprises. I was as thrilled as anyone to see gibbons, leaf-monkeys and a bug-eyed tarsier, not to mention a slow loris, but I’d seen them all in zoos and on TV so knew what to expect. But no one expects a sky-blue spider lurking in a hole in a bank, a purple-banded bee or an ethereal white praying mantis resting on a leaf.
And I love the camouflage some potentially tasty morsels come up with to avoid being eaten. Now you see it, now you don’t. Until it moves, the insect is indistinguishable from a leaf or a twig. I still marvel at the slow process of evolution that creates this perfect match for the inedible.
Leeches are like cats: they seem to gravitate towards the people who like them least. The most leeched member of our group emailed the day after her return to England. “Guess what I found when doing our washing? Yes, a very hungry leech! It is now flushed into England’s sewage works.”
This has science fiction film potential...
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