From wild to mild: Friendly foxes show changes in brain region

A study of silver foxes bred for friendliness examines how rapid domestication may reshape the brain. The breeding experiment began in Siberia in the late 1950s, after researchers noticed that some farm foxes were more accepting of human caretakers than others. Selectively breeding the friendlier animals produced foxes that interacted readily with people after just six generations; they also developed physical traits associated with domestication, including floppy ears and shorter snouts. Researchers now compared brain tissue from three tame, three aggressively bred and three wild foxes to investigate the neural changes linked to this shift in behavior.

The team focused on the ventromedial hypothalamus, a brain region involved in aggression as well as energy use, maternal instincts and social behavior. Using molecular markers to identify cell types, they found that tame foxes had fewer neurons expressing estrogen receptor alpha than the other groups. In mice, activating these neurons can trigger attacks, making them part of a known aggression circuit. The finding links fox tameness with a difference in a specific brain-cell population, but does not yet explain how selective breeding produces that change or establish its precise role in fox behavior. Researchers plan to investigate how genetic mutations influence the development of these neurons. The work also points to the possibility that environmental pressures can alter brain structure over relatively short timescales.