Just like humans, small rainforest apes called bonobos lose their appetites when food is placed on or near faeces.

Disgust towards such contaminants helps people to avoid exposure to pathogens. This knowledge prompted Cecile Sarabian at Kyoto University in Japan and her colleagues to test another primate’s reaction to potential sources of infection. The researchers offered bonobos (Pan paniscus) clean apple slices, apple slices covered in either faeces or soil, and banana slices placed at various distances from fresh faeces.

The animals tended to avoid contaminated fruit, and the likelihood that they would eat a piece of fruit rose as its distance from the source of contamination increased. Another experiment showed that bonobos are less likely to reach for food in the presence of unpleasant smells — such as the stench of rotten meat — than in an environment free of rank odours.

The team now plans to test whether bonobos confronted with contaminated food show the same facial expressions that humans do in similar situations.