Pseudocheirus peregrinus.
I check the possum's enclosure several times whenever I visit Hamerton - without seeing anything previously. So I was surprised and delighted to be able to see and photograph this individual enjoying a salad lunch.
@Lafone I checked the Marmoset House soon after I arrived, and saw the food on the shelf: but when I went back in the afternoon I ran into a party of young children on a trip - they were well managed, but excited to be at the zoo, so I expected that they would have disturbed any possums within earshot. Luckily, I was quite wrong.