They hoped the stuffed monkey and other cuddly toys would feel like a surrogate mother. She sleeps on the back of a toy cat, snug in a tightly wrapped towel.
Jess McKelson, a primate supervisor at the zoo, said that the past few weeks have been very anxious for everyone in her department.
'We're taking turns to stay overnight with Estela to monitor her condition and provide the overnight feeds,' she said.
'Keeping Estela alive has been a big challenge, and she has had ups and downs over this time, with several infections that have been a real threat to her survival.
'Our veterinary department has been right there for us, ensuring that Estela has had the best possible chance of surviving.'