Orang-utans at Melbourne Zoo celebrated the inaugural World Orang-utan Day with a picnic.

Two-year-old Dewi and his father Santan gobbled up fruit and sustainable palm fronds grown at the zoo in a special event to highlight the threat posed to their habitat by the African oil palm.

In Borneo and Sumatra, orang-utan habitat is being ripped up to plant the oil palm, which is used to make food and oil used in cooking.

Labelling laws allow manufacturers to describe palm oil as vegetable oil, which is found in about half of all packaged foods including cooking oil.

Activists want consumers to have a choice about buying food that comes from non-sustainable palm oil.

The zoo recently opened a display in the orang-utan sanctuary to try and educate consumers about making smart choices when they buy oil products.