The exoskeleton of the Lord Howe Island Stick Insect is such a deep, glazed black that it looks like it crawled out of a Flemish oil painting. When Jenny Gray, the CEO of Zoos Victoria, holds one in her outstretched hand (firmly cuffing her sleeve with the other), its long body stretches from the base of her palm to the tip of her fingers. Gray tells me that in the early twentieth century a ship ran aground on Lord Howe Island, the insects’ only habitat. Rats swam ashore and wreaked havoc on the wildlife, and the stick insect was declared extinct.

Around ten years ago, the phasmid got a second chance. A remnant group was found hanging off a shrub on a rock near the island and sent to Melbourne. The zoo successfully bred an insect Adam and Eve, and the population has grown each year since. Now there are a few hundred. It’s up to the NSW government to fix the rat problem. In the meantime, Melbourne Zoo has become an insect ark. Without it, the creature would be gone forever.

The stick insect is one of 11 threatened species harboured at the zoo, and there are plans to bring nine more aboard. “If we do nothing,” said Gray, “these animals will be extinct in the next five to ten years.” Gray, a South African who trained as a civil engineer and worked in banking, has an air of extremely sensible benevolence. Since 2008, she has worked closely with a new zoo board to change not just the fate of individual species, but what the point of the zoo is. When I spoke to Andrew Fairley, the chairman of the board, he explained: “It’s no longer a zoo. It’s a conservation organisation based at a zoo.”

The first zoo in Australia, Melbourne Zoo will be 150 years old in 2012. It opened just three years after Darwin published On the Origin of Species. That book forever changed how humans saw other animals, and many of those changes have played out at the zoo. For example, the zoo used to buy snakes from the public, they sold tigers to the circus, and they let a dingo roam free because he seemed so friendly. (Later, a keeper had to bite the dingo on the jaw when it attacked him.)

In 1931, the zoo lent a lion to an illusionist who was performing at the Tivoli Theatre. Unfortunately the lion cage wasn’t locked properly after the show, and the beast returned to the stage. The audience, believing it was an illusion, applauded wildly, but the orchestra knew better and, reported the Argus, began to play out of tune. The lion later strolled down Little Collins Street and into the Town Hall, where it was eventually coaxed into a box with a shin of beef. They wouldn’t lend out their lions again, said the director, Andrew Wilkie. He was quite interested, however, to add a Komodo Dragon to the collection.

Even the jolly stories from the zoo’s early days are like scenes from Bedlam. The tiger keeper’s wife walked a cub on a leash in Royal Park, children rode the elephants, and an orang-utan, who smoked cigarettes, burned its own cage down. When a baby hippopotamus was born, the zoo cracked open a bottle of champagne – and poured it over the hippopotamus. Absolutely everyone fed the animals. Melburnians brought in cakes, confectionary, lemonade, ice-cream and dozens of bananas, and after busy weekends the popular animals became ill – at which point the over-fed orang-utan was given a eucalyptus oil rubdown and a packet of laxatives. Another orang-utan wore clothes (navy-blue wool with scarlet trimming) and the keeper would occasionally bring it out of its small cage to shake hands. Children played with the orang-utan baby.

The day I visited Gray, I saw an orang-utan baby, too. I was 10 metres up, looking down from the roof of the large, three-part, climate-controlled orang-utan enclosure. The baby, which consisted entirely of limbs, coarse, sparky hair and big eyes, groped its way along a net to share an ice block with the dominant male. Next to me, a keeper threw in objects whose sole purpose was to engage an ape. The fruit-filled ice blocks, rubber balls with tufts of straw poking out, and plastic panel with raisins jammed into little holes encourage the animals to solve problems as they would in the wild. It is a long way from the well-intentioned but deeply goofy anthropocentrism of the zoo’s Victorian-era orang-utan diet, which included eggs, buttered toast, bread with jam, tea and the occasional bottle of whisky.

These apes work, too. Their visitors encounter the zoo’s ‘Don’t Palm Us Off’ campaign. More than 1000 orang-utans die every year because their forests are cleared to produce palm oil, an ingredient in many products found in Australian supermarkets. If deforestation for palm oil production is left unchecked, orang-utans will likely become extinct. The problem is that consumers can’t choose not to buy products that use palm oil or to buy products that use sustainably produced palm oil because it’s not labelled on the ingredient list. The zoo’s campaign promotes clear palm oil labelling so that consumers can choose.

It has been a great success. The European Zoo Association took up the idea, and the European Union has since made oil labelling mandatory. In Australia, Senator Nick Xenophon is pushing for the same. Even the Malaysian Palm Oil Council – who wish, let’s be clear, to conceal the name of their own product – sent a delegate to Melbourne. He observed an orang-utan under a sack on a rainy day and told Malaysian journalists the zoo was cruel to its animals.

Like most zoos, Melbourne Zoo has been thinking seriously about conservation since the 1960s, but it is the first in Australasia, and possibly the world, to make sure that everything that happens at the zoo – whether it’s ostensibly about education or entertainment – is underwritten by the commitment to conservation. ‘Don’t Palm Us Off’ is just one of its campaigns, and so far the reaction from zoo visitors has been encouraging. Even in this era of climate change and species extinction, the zoo is hopeful that it can do more.

Unlike other conservation societies, Fairley said, “we have a special relationship with our subscribers – we see them every weekend.” The animals have changed, too. They are now ambassadors, enablers and guardians of their gene pools. They must be treated respectfully, but they must all do work for their wild cousins, admittedly from within the zoo. I asked Gray if she would lend me a lion. “Unlikely,” she replied.