The freak appearance of a crocodile in a New Territories river brought much-needed attention to the polluted state of Hong Kong's northern waterways, but in their natural habitat, crocodiles can be an environmental guide. John Lever, who spent two weeks trying to catch the rogue Yuen Long reptile, has recently begun a programme in conjunction with the Australian government to use crocodiles as indicators of river health in Queensland and the Northern Territory.
'Because a crocodile is at the end of the food chain, whatever is polluting a stream ends up in the croc,' said Mr Lever, who has returned to Australia. 'If you can then take some part of the croc and monitor on an annual basis you can then track changes in the river environment.'
He had originally suggested the plan to Papua New Guinean authorities in the late 1970s as a way of monitoring the effects of mining operations in the Fly and Purarie rivers, where he originally learnt to catch the reptiles.
The plan was rejected and the Fly has since become an environmental disaster area.
Mr Lever's Australian programme uses crocodile eggs to monitor streams.
'The egg is a reflection of the mother, so if there is any change in the level of pollutants she is ingesting then it should show up in the eggs.