Chester Zoo is to receive a prestigious animal welfare award for the work it has done with its mandrills.
Mandrills are classed as vulnerable in the wild (pic from Chester Zoo)
A team from the Cheshire zoo and Durham University carried out a study on the behaviour of the vulnerable monkeys.
They found planting a barrier of small shrubs between the mandrills' enclosure and the visitors' viewing area reduced their stress levels by 54%.
They are to get the Universities Federation for Animal Welfare (UFAW) Wild Animal Welfare Award.
It will be presented by TV vet Steve Leonard.
The planting was carried out by the zoo's Horticulture and Botany Department.
The study also showed a rise in the social behaviour of the seven-strong mandrill group.
'Ask' the animals
The zoo's research officer, Dr Sonya Hill, specialises in primate behaviour and welfare and supervised the research within the zoo.
The work was carried out by Durham students Riccardo Pansini and Jessica Hargreaves.
Dr Hill said: "Good animal welfare is at the forefront of Chester Zoo's mission, and I am delighted that we have won this prestigious award, which recognises the contributions that our scientific collaboration has made to the lives of the mandrills.
"By assessing animal welfare, we can 'ask' the animals what they want, and this helps us provide conditions that meet their needs for good welfare.
"Life in the wild is not always stress-free either, and the more we learn about each species, the more we understand what behavioural strategies they use to cope with things in their environment."
As part of the award, the zoo will receive £1,000, which will go towards further research into animal behaviour at Chester Zoo.