Dawn breaks, with a crash.
Through a tangled thicket of branches and vines comes a roar as two hefty beasts charge. Lions! The commotion triggers a nervous giggling squeak familiar to Tarzan viewers of a certain age. Chimpanzees! It sets off an indignant rumble. Wide load coming through! Rhino-ceroses! A distant growl gathers menace, like a storm. The sound of vehicles seemingly gearing up for safari sits heavily on the air; and as I venture gingerly, nose first, beyond a soggy tent flap, my bleary eyes slowly focus on one of the world's most magnificent vistas. Far beyond a thousand boats jiving offshore, and through the mists of early morning, stands ... the Sydney Harbour Bridge.
Sydney, Australia: nowhere near Africa. Sydney: home to creatures of bush, plain, swamp and mountain. All reside at Taronga Zoo, on the harbour's north shore. Out with the bars, and as many cages as possible, have gone the monkey circus, elephant rides and miniature train. Along with a growing responsibility for preservation have arrived a lecture theatre; an education centre; a free-flight bird show; the Great Southern Oceans enclosure, to be inaugurated by penguins, sea eagles and sea lions in 2008; and the Asian rainforest zone, based around waterfalls and a stream linking the accommodation of Malayan tapir, silvery gibbon, binturong and fishing cat.
It is Taronga's passion for education that sees me holed up in a tent, listening to the snuffles, coughs, grunts and wheezes of some peculiar-sounding creatures of the night. They are all two-legged fellow slumber-party animals spending 24 hours learning how and why a major zoo functions. The Roar and Snore sleepover programme runs year round; its popularity is rampant, so spots during school holidays are hard to get. And New Year's Eve (more of which later) is a guaranteed sell-out, so book early.
Many crafty parents have done just that for the night my pseudo-safari partner and I are there: adults are only just outnumbered, 14 to 13, by children. We arrive on time, 6.30pm, and immediately feel like Johnnies-come-lately: we expected we'd have to put up our own tent, with all the usual comical lack of co-ordination, but the night's team of three zoo keepers (called 'educators' these days) have done all the hard work.
At the feeding area, the evening is gathering pace. A dominant species is making short work of the cheese platters, dips, chips and beer, while its young wait patiently for the real adventure to begin. It does when our educator guides, identifying themselves by their stick-on name tags, on which they have drawn their favourite animals, bring out the first stars of the evening's show.
Annette the koala, Vikki the wombat and Liana the giraffe introduce a pinecone lizard (rescued when the computer in which it was being smuggled was intercepted), a leaf stick insect capable of regrowing missing legs (an ability we take on trust), an inquisitive, tank-like wombat keen on biting toes, an abandoned koala clinging to its teddy-bear surrogate mother and a carpet python that needs nobody's sympathy. The creatures are here to be petted; strangely, the koala receives more 'hits' than the python.
The koala, says Annette, has just about been weaned. 'Does anybody know what weaned means?' she asks.
'She's had her willy chopped off!' announces a future David Bellamy.
Cautiously, we set out into the night. The koalas are found frantically conserving energy in their eucalyptus trees; a reticulated python and its boa constrictor chum personify the deadly sin of sloth; and the Himalayan tahrs have settled in for the evening on the precarious ledges of their 'mock-rock' plaster-cast mountain.
None of which prepares us for perhaps the most electrifying sight in any wilderness, even a man-made version. Sensing intruders in his personal space, a muscular young lion bounds towards the group, all mane-flaring menace and teeth. The king of this particular jungle noses up to the glass keeping us out of his lair; gasps rise from the darkened viewing pit. Standing on higher ground, he has uncontested dominion.
We retreat to the kitchens. Taronga's seals are gastronomically flattered daily with a diet of top-dollar seafood. Its bandicoots, potoroos, quolls and possums are no less carefully catered to, although their palates are different. A possum treat is a high-energy drink made with nectar, which, in the spirit of journalistic inquiry, I try. It tastes like honey. I can't stand honey. Next on the menu is 'animal chocolate', promises Annette; the other name for this is mealworms, gallantly and exclusively sampled by Lara the lion, assisting the educators as an enthusiastic member of Taronga's Yatz (Youth at the Zoo) initiative. Never have I been so relieved to declare myself a vegetarian.
Dinner proper comes back at the education centre, but doesn't feature any inmates. Nor does it feature anything like the rat popsicles kept in the animal kitchen freezer for dangling (after defrosting) from cords around the lions' den. Enticing animals to work for their food is called 'enrichment' and prevents them growing lazy and fat.
That is the danger we face at a trestle table covered in chicken, beef and lamb kebabs, buckets of salad, crusty bread, cheese and biscuits, wine, beer and soft drinks. A short waddle to the tents and we are ready for hours of faux terror surrounded by the sounds of the jungle. There follows a long, wet night of the soul, of sleeping bags soaked by osmosis on touching the sides of the tent and a morning of tipping water from shoes left outside.
To avoid the risk of drowning, breakfast is brought forward to a bracing 5.30am, setting up the group for a couple of special early visits and the rest of the day at leisure. We aren't the only ones scoffing. Down at its harbour-vista enclosure, the ravenous giraffe herd is engaged in engineering a world carrot shortage. We are allowed in to help; to keep finger complements full, vegetables are nervously gripped low down.
Every zoo guarantees strange sights, but few can be as bizarre as pigs playing football. However habitually mocking their bad press, pigs are in fact rather intelligent and Taronga's porcine stars make short work of their enrichment test. Wilbur and Clementine know that kicking or 'heading' their footballs with their snouts will eventually reveal the fresh-vegetable feast concealed within. But pity their poor keepers because theirs is a bum rap. Australia is normally hot; pigs spend hours snuffling through the dirt with their tender pink backsides in the air. To those backsides the keepers must apply sunscreen.
The football match isn't quite the end of the fun, games ... or fireworks. Every New Year's Eve, Sydney throws one of the world's biggest parties, along with a harbourside fireworks display. Like Hong Kong, Sydney suffers an unseemly scrum as spectators jostle for position; happily for Taronga, it occupies an unrivalled vantage point, with unbroken views of the harbour. Animal compounds remain open until early evening, after which the human entertainers take over. Last New Year's Eve, the Northern Strings ensemble brought to life Bach, the Beatles, Mozart and Vivaldi in one section of the grounds; the Swing City big band shook, rattled and rolled another, and even offered dancing lessons.
Guest numbers are limited and gourmet picnic hampers are available to partygoers, who are encouraged to spread out, recline on their blankets and take the fireworks lying down.
And then there are the really privileged creatures who combine these one-night, big-ticket, big-bang thrills with a Roar and Snore sleepover ... but they are rare beasts indeed. See www.zootopia.com.au  - and book early.
Getting there: Virgin Atlantic (www.virginatlantic.com ), British Airways (www.ba.com ), Qantas (www.qantas.com ) and Cathay Pacific (www.cathaypacific.com ) fly from Hong Kong to Sydney. Roar and Snore sleepovers cost A$104.50 ($590) for children aged five to 17 and A$155.20 for adults.