A team of researchers has found a simple and unique way to considerably reduce stress levels and increase the welfare of monkeys living in a popular zoo.
The study, carried out by Durham University with Chester Zoo, found that planting a metre-wide barrier of tropical shrubs between the monkeys' glass-fronted enclosures and the visitors' viewing platforms reduced the animals' stress-related behaviour by more than half.
The techniques developed in the study have now won the praise of animal welfare scientists, who have awarded the research team with the prestigious Universities Federation for Animal Welfare (UFAW) Wild Animal Welfare Award for their work.
The study investigated the stress levels of a type of monkey known as a mandrill, which is one of the exotic animals bred at Chester Zoo, in North West England. Seven mandrills , which are the world's largest monkey species and whose native habitat is the tropical rainforests of Central and Western Africa, are kept at the 110-acre Zoo. In the wild, mandrills have been classed as vulnerable (World Conservation Union Red List of Threatened Species 2006) meaning that they face a high risk of extinction in the medium-term future.
The research team monitored the mandrills and found that the presence of visitors so close to them at the glass window caused them to exhibit behaviour which experts say could be considered abnormal, such as showing their teeth and pacing.
Following advice from Chester Zoo's primate keepers, researchers worked on a strategy to provide more cover for the mandrills, and tested a technique which involved planting shrubs between the monkeys' viewing windows and the visitors' platform.
The tropical shrubs, which increased the distance between the visitors and the monkeys' viewing windows by one metre, consisted of a range of plant species selected by Chester Zoo's Horticulture and Botany Department. Once the plants are thickened out, they will provide an attractive ,barrier, and give visitors a more naturalistic impression of how the animals would live in dense forests in the wild.
In addition to the significant overall improvement in the animals' welfare after the shrubs were planted, the researchers found that stress-related behaviour specifically directed at the visitors, such as approaching the glass, reduced by 54 per cent. Instead, the type of behaviour monkeys would show in the wild, such as climbing and eating, increased by 13 per cent. The study also showed a 16 per cent rise in sociable behaviour, such as playing and grooming each other.
Dr Jan de Ruiter, a lecturer with Durham University's Department of Anthropology who led the research, said: "We initially found some levels of stress among the mandrills. Their behaviour showed signs of anxiety and social tension. Visitors can further aggravate this stress as some people interpret the mandrills' behaviour as amusing and start mimicking them."
Dr de Ruiter added: "As soon as the shrubs were positioned, we noticed an immediate improvement in the welfare of the mandrills, who displayed significantly less anti social behaviour. The botanical display also adds to the visitor experience as they gain a more natural impression of the type of environment in which the mandrills would be living in the wild in Africa."
The research team says its work has potential for further application in the care of monkeys, and other zoo animals.