Clean living is a luxury wild animals can't afford, study suggests

A study of wild mice has shown that they prefer to sleep and eat near to used nesting material and droppings left by other mice.

Choosing a safe place to sleep and taking the opportunity to eat outweighs an increased risk of disease from other animals' dirt, the findings suggest. The study is significant because it could help improve scientists' understanding of how disease spreads among wild animals.

Scientists say the wild mice's behaviour contrasts with that of clean-living domesticated animals, which tend to develop an aversion to dirt. Pets and domestic animals have plentiful food and are less at risk of being targeted by predators, and so they can be choosy about where they eat and sleep, researchers say.

Scientists from the Universities of Edinburgh and California Santa Cruz studied two types of wild mice in Virginia. Animals were collected from woodland and placed in a box for a few hours, with the option of being close to mouse droppings or not. A similar experiment was conducted with new and soiled nesting material.

They found that the animals preferred being near droppings and second-hand nest material, regardless of whether there was an increased risk of contracting parasites in either case.

Dr Patrick Walsh of the University of Edinburgh's School of Biological Sciences, who took part in the study, said: “Domesticated animals generally avoid faeces to reduce the chance of parasitic infection, but this study shows that wild animals are more concerned with the risk of starvation than with table manners, taking any opportunity to feed. They may even associate faeces with safety – a spot where a mouse has lived long enough to nest and poo is probably pretty safe – and that is worth the risk of disease. This helps us learn more about how diseases spread in the natural world.”

The study, published in the journal Animal Behaviour, was supported by the Wellcome Trust.