How does Douglas Adams use imagery in Last Chance to See?

Imagery:

"That was the extraordinary thing. We actually did find the creature. We only caught a glimpse of it for a few seconds, slowly edging its way along a branch a couple of feet above our heads and looking down at us through the rain with a sort of serene incomprehension as to what kind of thing we might possibly be, but it was the kind of moment about which it is hard not to feel completely dizzy."

"Sleeping in Labuan Bajo, however, is something of an endurance test.
Being woken at dawn by the cockerels is not in itself a problem. The problem arises when the cockerels get confused as to when dawn actually is. They suddenly explode into life, squawking and screaming at about one o'clock in the morning. At about one-thirty they eventually realise their mistake and shut up, just as the major dogfights of the evening are getting under way. These usually start with a few minor bouts between the more enthusiastic youngsters, and then the full chorus of heavyweights weighs in with a fine impression of what it would be like to fall into the pit of hell with the London Symphony Orchestra.
It is then quite an education to learn that two cats fighting can make easily as much noise as forty dogs. It is a pity to have to learn this at two-fifteen in the morning, but then the cats have a lot to complain about in Labuan Bajo. They all have their tails docked at birth, which is supposed to bring good luck, though presumably not to the cats.
Once the cats have concluded their reflections on this, the cockerels suddenly get the idea that it's dawn again and let rip. It isn't, of course. Dawn is still two hours away, and you still have the delivery-van horn-blowing competition to get through to the accompaniment of the major divorce proceedings that have suddenly erupted in the room next door.
At last things calm down and your eyelids begin to slide thankfully together in the blessed predawn hush, and then, about five minutes later, the cockerels finally get it right."