Friday, June 30, 2006

Chameleon Snake, and Internal Ant Pedometers

Returning from an army training exercise in Brunei, I saw on the news, after stepping off the plane, news that a snake which can change its colours has been found in the heart of Borneo. Having been on the same island as that snake for three weeks without knowing of it made me rather disappointed that I didn't see anything quite as remarkable or vivid while I was there. According to the report on BBC News, the snake is a venomous rear-fanged water snake and was found to possess its colour-changing property when it was put into a dark bucket. When it was retrieved, its original reddish-brown colour had become almost white. What significance this chameleon-like property has is unknown, though it might be a response to a stressful situation, since to become white it would presumably retract the pigments within the chromatophores in its skin. The mechanism by which this colour-changing act works is probably similar to that in changeable lizards like the chameleon, since both lizards and snakes are in the class of Reptiles.

Also rather recently, some Saharan desert ants have been found to use a sort of internal pedometer to count the number of paces they take when they move about, to aid in navigation. Instead of simply tracing back over the trail they took to reach a certain location to return to their nest, they can return via a direct route. To do so they need to know what direction they are facing, and what distance they have covered. For direction, they've been found to use the sky to orientate themselves, but for distance, no one knew until an experiment was conducted to see if the ants counted their steps. These ants had their legs either extended with stilts or shortened by amputation, and were set free to make their journeys. Those with extended legs overshot their target while those with shortened legs fell short, showing that they probably relied on the number of steps taken, rather than some external guide to distance. And this, of course, was part of what I was doing in the forests of Brunei, counting my paces while others took bearings with a compass and still others plotted the journey on a map. Unfortunately my instinctive abilities of navigation are no where as good as the natural abilities of ants and other animals, so it was good that we had GPS to back us up. Else I'd still be in there, somewhere, see?


Ivan Chew said...

This message is probably for Siva -- I found my way here from Brandon's comment. Darn, you REALLY should have an "About" post, Siva. Ok, your description is quite self explanatory but ah, I guess I tend to want to know more what this is about. :)

Sivasothi said...

Well, I thought I could leave readers to check the very first post but I guess that's not clear.

I am not looking forward to republishing the blog in blogger though. It's not a smooth process!