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It's been a big year for Madju. He's moved from breast milk on to solid food, cut 12 teeth and now he's starting to walk.

And yesterday Auckland Zoo's Bornean orang-utan celebrated his first birthday.

"I haven't got enough fingers and toes to count the number of people who come to the zoo especially to see him," said senior primate keeper Christine Tintinger.

"People know him from the TV show [The Zoo] and watched the progression of his mother Melur's pregnancy. They also can't get enough of him, just because he's so cute."

Though Madju (Indonesian for progress) has grown this year, he's still very small - just 4kg. He still spends most of his time attached to his mother or learning to use sticks as tools to get food from holes.

But sometimes he will branch away from his mother to play close by. "It's amazing what fun he can have with a bit of stick or a box," said Ms Tintinger.

During his second year, staff expect him to become more independent, as well as eating more of his favourite food. "He loves sucking on the ice-blocks we make him from sugar-free cordial, just like any good Kiwi kid."

Ms Tintinger said even though he is only turning 1, Madju is starting to show signs of "the terrible twos".

"He's already becoming more mischievous and sometimes runs away from his mother."

For Madju's birthday the zoo erected a marquee, had free giveaways, and gave children a chance to sign Madju's giant birthday card.

The zoo used the celebration to mark the beginning of Orang-utan Caring Week, to highlight the plight of Bornean orang-utans. Ms Tintinger said they face extinction in the wild in as little as three years because of deforestation and production of palm oil.

The risk of losing the species was further heightened because orang-utans bred only every eight years.