Monster leech sucks down giant worm like spaghetti #WondersofTheMonsoon BBC2

'Wonders of the Monsoon' starts on BBC2 5/10/14
Please Note: The leech that we filmed was 50 cms long, half a metre.
This story was first published by the Telegraph 26/Sept/2014

On Mount Kinabalu in Borneo lives the legendary Giant Red Leech - one of the biggest leeches in the world. Fortunately they don’t have a taste for blood, instead they hunt giant blue worms and suck them down like spaghetti, revealed for the very first time in our new BBC 2 series ‘Wonders of the Monsoon’.

Cameraman Richard Kirby and I travelled to Mount Kinabalu in Borneo in the hope of catching a glimpse - what we managed to film was simply gobsmacking. We joined ecologist Alim Biun who was keen to study the elusive animal.

The giant leeches are so mysterious that they don’t even have a full scientific name. “Very little is known about them, we don’t know how they hunt, or even how big they grow, because no one has researched them” said ecologist Alim Biun.

Finding the species on mount Kinabalu, the biggest mountain in Borneo, was a huge challenge. But if you want to film a predator the best thing to do is to find its prey, but it took us several weeks of searching before an extremely heavy rainstorm eventually brought worms out in huge numbers. Sure enough the red leeches were not far behind. Alim and his team quickly collected specimens and moved them to an open area, where the scientists could see what was going on.

By working with Alim we were able to sufficiently light the area of forest to record the predation as it unfolded It was exciting and fascinating, as he was making his new scientific discovery, we were documenting the behaviour for the very first time.

Our extraordinary new footage reveals how the giant leech (the leech in the video is 50cms long) is able to quickly detect a worms trail, and like a sniffer dog follow it and latch on to its prey. “There are many sense organs on the bottom surface of their oral sucker and they can probably sense the chemicals and the shed cuticles of the worms.” said Leech scientist Dr Takafumi Nakano of Kyoto University


Dr Nakano who has studied a much smaller relative of the Giant Kinabalu Leech said “When they eat too large or too many earthworms, they often throw up portions or whole body of the worms.” This is behaviour similar to that seen in large snakes, like the reticulated python. With poor vision the snake has no accurate way to tell how big the prey is and so they keep on swallowing until its too much - with no way to bite off a chunk they have no option but to regurgitate the prey. This is the same behaviour we saw a few times with the giant leech allowing the worm to make a quick exit.
The whole process of swallowing the worm lasted about 15 minutes and then the leech disappeared under leaf litter, coiling up to digest its meal. Dr Nakano estimates that it would take about a month for the leech to digest the worm. The result is that we can confirm the predatory behaviour of a rarely-seen and unidentified species for the first time.