Scientists studying the brains of silver foxes have identified differences in the ventromedial hypothalamus, a region at the base of the brain associated with aggression, energy-use decisions, maternal instincts and social behavior in mice. The findings come from a study comparing foxes bred for tameness, foxes selected for aggressive traits and wild foxes.
The research, published November 2 in Current Biology, draws on a breeding experiment that began in Siberia in the late 1950s. Russian geneticists observed that some foxes on silver fox farms were more accepting of human contact, while others behaved aggressively. By breeding the friendlier animals with one another, they produced foxes that interacted with people after six generations. These animals also developed physical traits associated with domestication, such as floppy ears and shorter snouts.
The researchers examined nine preserved fox brains supplied by scientists working with a Russian fox colony: three from tame foxes, three from aggressively bred foxes and three from wild foxes. Using fluorescent RNA labeling on thin brain sections, they identified different cell types in the ventromedial hypothalamus.
The team focused on neurons expressing estrogen receptor alpha because previous mouse studies had linked these cells to the aggression circuit. In those experiments, activating the neurons caused mice to attack another mouse. The tame foxes in the new study had fewer estrogen receptor-expressing neurons in this brain region than the other groups.
Senior author Eirene Markenscoff-Papadimitriou said the work was intended to clarify the neurological basis of behavioral changes produced rapidly through selective breeding. She also said the findings suggest that environmental pressures can alter brain structure over relatively short timescales.
The researchers now want to determine how domestication produces these changes in the ventromedial hypothalamus. Co-author Anna Kukekova may investigate how mutations in different parts of the fox genome influence the development of the neurons identified in the study.
The paper, by Jared L. Klein and colleagues, is titled “Hypothalamic cell-type differences associated with selection for tameness in the silver fox.” Its DOI is 10.1016/j.cub.2026.09.020.
Sources: Phys.org.