Last Chance to See by Douglas Adams, Mark Carwardine

and muscular sloping ridge tent.
    You will have heard it said before that these creatures are awesome beasts, and I would like to add my own particular perception to this: these creatures are awesome beasts. It is hard to know how better to put it. A kind of humming mental paralysis grips you when you first encounter a creature such as this in the wild, and indeed there is no creature such as this. All sorts of wild and vertiginous feelings well up into your brain, that you seem to have no connection with and no name for, perhaps because it is thousands or millions of years since such feelings were last aroused.
    I'm going to be a bit fanciful for moment, because it is very hard not to be when your rational, civilised brain (f use the words in the loosest possible sense) experiences things it has no way of recognising or accounting for but which are nevertheless very powerful.
    I've heard an idea proposed, I've no idea how seriously, to account for the sensation of vertigo. It's an idea that I instinctively like and it goes like this.
    The dizzy sensation we experience when standing in high places is not simply a fear of falling. It's often the case that the only thing likely to make us fall is the actual dizziness itself, so it is, at best, an extremely irrational, even self-fulfilling fear. However, in the distant past of our evolutionary journey towards our current state, we lived in trees. We leapt from tree to tree. There are even those who speculate that we may have something birdlike in our ancestral line. In which case, there may be some part of our mind that, when confronted with a void, expects to be able to leap out into it and even urges us to do so. So what you end up with is a conflict between a primitive, atavistic part of your mind which is saying, jump!' and the more modern, rational part of your mind which is saying, `For Christ's sake, don't.'
    Certainly the dizzy experience of vertigo seems to have far more in common with feelings of oscillating mental conflict and confusion than it does with simple fear. If it is a fear, it's one we love to play with and tease ourselves with, which is how designers of big dippers and Ferris wheels make a living.
    The feeling I had looking at my first silverback gorilla in the wild was vertiginous. It was as if there was something I was meant to do, some reaction that was expected of me, and I didn't know what it was or how to do it. My modern mind was simply saying, `Run away!' but all I could do was stand, trembling, and stare. The right moment for something seemed to slip away and fall into an unbridgeable gulf between us and the gorilla, and left us simply gawping helplessly on our side. The gorilla, meanwhile, seemed to notice that we had been busy photographing its dung and merely stalked off into the undergrowth.
    We set off to follow it, but it was in its own element and we were not. We were not even able to tell whereabouts in its own element it was and after a while we gave up and started to explore the area more generally again.
    The gorilla we had seen was a large male silverback. `Silverback' simply means that its back was silver, or grey-haired. Only the backs of males turn silver, and it happens after the male has reached maturity. Tradition has it that only the chief male of a group will develop a silver back, and that it will happen within days, or even hours, of it taking over as leader, but this apparently is nonsense. Popular and beguiling nonsense, but nonsense. And while we are on the subject of nonsense I should mention something that we discovered a few days later when talking to Conrad Aveling, a field researcher in Goma who has for years been responsible for gorilla conservation work in the area.
    We told Conrad how alarmed we had been by Murara and Serundori's accounts of simply going out and mowing down the local poachers, and he sat back in his chair, kicked up his heels and roared with laughter.
    `It's incredible what these guys will tell the