An infant gorilla at Bristol Zoo Gardens is being cared for by a surrogate mum after being hand-reared since birth.
Nine-month-old Hasani had to be under careful watch by keepers as his biological mother, Kala, struggled to look after him.
Keepers tried to re-introduce to pair together on a number of occasions but were unsuccessful – until they handed him over to 16-year-old Kera.
Lysney Bugg, the curator of mammals at Bristol Zoo, said: "Although Kera had no rearing experience, she is very intelligent and we have been able to nurture her behaviour.
"She has seen several other females rear their youngsters and so had a good foundation on which to build on.
"All the way through hand rearing, Kera was keen to spend time with Hasani and the two always seemed to get on very well.
"This is a fantastic success. We have taken a young gorilla that would otherwise have died and turned him around and he is back with his fellow gorillas inside of a year. It is an amazing achievement."
Hasani, which means ‘handsome’ in Swahili, was tentatively introduced to Kera through an open partition that only he could pass through.
They were desperate to get Hasani and his mum Kala together but she continued to reject him.
Lynsey, who is also an advisor on surrogacy for the gorillas' EAZA Ex-situ Programme (EEP), said: "We really wanted to get them back together and give Kala another chance to look after him.
"Once Hasani was sufficiently mobile and physically ready for it, we felt the time was right to try them together again.
"But despite Kala being very keen to begin with, over time she continued to show the worrying signs of not being able to cope.
"We really tried everything we could every day over several weeks but in the end we had to accept that it wasn’t working."
Kera gave birth to a daughter, Afia, five years ago but she had to give her up to another surrogate mother because of illness.
It means Hasani is the first infant she has had to look after but the pair are already making good progress and will spend the next three to four years together.
Lynsey said she was now working on plans to introduce Hasani to the other western lowland gorillas.
She said: "Hasani has been near the other gorillas every day and has heard their calls and sounds, so he is used to them.
"He is developing nicely; he’s very mobile and is eating well. He’s also starting to copy Kera in natural gorilla behaviours such as nest building and stripping bark and leaves from branches.
"He will grow up to be a fully-functioning gorilla thanks to the efforts of his dedicated keepers."