Ripping yarns from a rugged kinda guy

Tim Flannery has been described as the "Indiana Jones of Science". On the cover photo, he even has the hat. Yet how he must hate the expression. It is the sort that clings as tenaciously as the smell of a male tree-kangaroo. Flannery is indeed something of a white-water zoologist, a great discoverer of unknown species, an explorer of little-trod places. Danger, disease and ratmeat are his everyday fare.

Throwim Way Leg documents his career as a fieldworker in parts of New Guinea that are most kindly described as "rugged". He biffs his way up mountains and into caves and through swamps in the service of science, initially on foot and - with increasing seniority - more and more by well-funded helicopter. The highpoint of his career is the discovery and documentation of an unknown tree-kangaroo called a dingiso. A photograph shows it to be irresistibly endearing.

At least he has a good reason for all this suffering. His is not simply one of those artificially constructed challenges, like the urge to be the first man to cross New Guinea on a pogo stick. Or is it? Curiously, nowhere in this most readable book does he feel the need to explain just what is so desperately important about potting another unknown species of bat or even intestinal parasite and tagging it with his name in a museum drawer. What is it that makes it worth all the pain and expense and disruption to other people's lives?

But this conviction of a divine mission is probably just the other face of an all-consuming enthusiasm that makes him an eloquent exponent of his field and a most agreeable guide to its highs and lows, the thrill of discovery and the frustration of failure. A trained scientific classificatory zeal does not preclude a true love of the natural world that he communicates to the reader with power, poetry and conviction. Alas, nowhere is there a picture of a long-beaked echidna but his description makes me want one for Christmas.

Chasing animals involves human contacts, eccentric missionaries, disagreeable big men, manly hunters, incompletely reformed cannibals, disingenuous bureaucrats. In all these encounters Flannery comes across as flexible to the point of ethnography and unpacks his bag of anecdotes with verve and wit. In places this is a very funny book and handled with a lightness of touch. Cultural misunderstandings are a constantly exploited seam. The native rejigging of the priests' hell as a jolly place full of dark figures and a cheery fire is a classic.

But little by little, human and ethical problems seem to creep darkly into the margins of the text like increasingly troublesome pests that just will not go away no matter how much you swat at them. Locals are not always co-operative, having been abused in the past by other collectors. They see wildlife as belonging to them and may even have kinship links with certain animals. In his early phases Flannery has a romantic attraction to the exotic. But we soon see that the authenticity of traditional culture and its relative freedom (for men) from exploitation has to be balanced against the lure of modernisation and the material benefits this can bring. What is "right"? And is Flannery's strategy of slaughtering endangered species for collection really the best way of conserving them? He is ill at ease with a TV crew who behave like an invading army. And in Irian Jaya he is even more touchy about an invading army, the Indonesian, who try to pretend they are mere administrators and security men in what is just another act of modernisation in just another province of Indonesia. Racism, brutality and - maybe - murder move from offstage to the centre of his concerns in the giant Freeport copper mine of Tembagapura, where Javanese and Americans collaborate to exploit the world's richest deposits, worth $10 million a day. Frequently seen as an ecological disaster, the area appears in Flannery's carefully judicious account as offering rich new niches for human exploitation. Then a local boy is viciously beaten for being in the wrong place at the wrong time. Flannery takes him to the hospital where he mysteriously dies. Flannery makes ineffectual noises about the boy. Should he do more? Should he do less? He worries about the ethics of biting the hand that bribes him with fieldwork facilities, and - this quite without irony - names a rat after the boy as recompense. I think you probably have to be a zoologist to understand that.

The book is prefaced by a dedication to the chief executive officers of mining companies in the hope that it will help them understand the people whose lives they change. The animals, oddly, are not mentioned.

Nigel Barley is assistant keeper, Museum of Mankind.