Wild house mice change appearance after contact with humans

White patches on brown fur are a sign of self-domestication Linda Heeb

Researchers from the University of ZurichExternal link (UZH) have shown for the first time that wild mice living in close proximity to humans end up looking different within a decade. Their results could provide clues about how domestication began in other animals like dogs. 

The researchers found that mice (Mus musculus domesticus) living in a barn near Zurich started developing white patches on their brown fur as well as shorter snouts within a span of ten years. No attempts at selective breeding were made and the only intervention was provision of food and water. 

“The mice gradually lost their fear and developed signs of domestication. This happened without any human selection, solely as a result of being exposed to us regularly,” said studyExternal link leader Anna Lindholm. 

Changes in appearance due to human intervention have been observed before in animals like Siberian foxes. However, this change was a result of selective breeding for a particular trait like friendliness, for example.

The transformation has been linked to stem cells in the embryo called neural crest that affect both behavioural and physical traits in parallel. Thus, by selecting timid animals and breeding them, researchers unintentionally had an effect on their physical appearance. 

But the wild house mice were not selected in any way. According to Lindholm, the “self-domestication” by the mice themselves led to gradual changes in their appearance “incidentally and inadvertently” much like selective breeding of Siberian foxes. 

This self-domestication could offer clues into how wolves developed into domestic dogs, says the UZH study, which was published in the journal Royal Society Open Science on March 7.