A study published in Mammalian Biology confirms hybridization between the European polecat (Mustela putorius) and the domestic ferret used for hunting (Mustela putorius furo), based on genetic analysis. This scenario may compromise the genetic integrity of wild populations and raises concerns about the implications for wildlife conservation in the Iberian Peninsula. The work was led by the University of Cádiz (Spain) and includes Victor Bandeira, a member of CESAM and the Department of Biology at the University of Aveiro.
The European polecat, a wild relative of the domestic ferret, is a small carnivore widely distributed across Europe. However, its populations have declined in several regions due to habitat loss, human persecution, and other anthropogenic factors such as road collisions, leading to its classification as “Endangered” in Portugal in the most recent edition of the Red Book of Mammals of Mainland Portugal. The release or escape of domestic ferrets facilitates contact with polecats, promoting crossbreeding that may go unnoticed.
From an evolutionary perspective, the ancestral origin of the domestic ferret remains a subject of scientific debate. Some authors propose that it descends from the steppe polecat (Mustela eversmanii), while others consider the European polecat itself to be its wild ancestor. In any case, the ferret is currently commonly treated as a domesticated subspecies of the polecat, a view adopted in this study. This close relationship explains why hybridization is biologically possible and why, in many cases, hybrid individuals cannot be easily distinguished based solely on external appearance.
In this study, the research team analyzed genetic samples from polecats that had been killed on roads in different regions of Spain, as road mortality is one of the main threats to the species. Polecats inhabiting agricultural ecosystems often specialize in preying on rabbits, which are particularly abundant along road verges, and are therefore at risk of being run over when accessing burrows. In parallel, the authors collected blood samples from domestic ferrets used for rabbit hunting in several Spanish provinces, with the owners’ permission. This approach made it possible to detect cases of genetic introgression—that is, the exchange of genetic material between domestic and wild individuals—thus confirming the existence of hybrid individuals in the wild.
One of the most notable aspects of this work is its strong citizen science component. The collection of biological samples from polecats was made possible through the collaboration of numerous volunteers involved in the project “Distribución, Conservación y Ecología del Turón en la Península Ibérica,” as well as environmental agents and staff from wildlife rehabilitation centers across the country. This collaborative network enabled the collection of samples from different locations in Spain, significantly expanding the geographical scope of the study and allowing for a nationwide genetic analysis.
The results reveal high hybridization rates for both taxa, with 15% of ferrets and 35% of polecats analyzed showing some degree of hybridization. Consequently, some specimens initially classified as pure polecats or ferrets were in fact hybrids. Furthermore, the authors identified a first-generation hybrid specimen, the offspring of a polecat mother and a ferret father, confirming the illegal removal of wild individuals from their natural environment for captive breeding purposes. These findings demonstrate that hybridization is not merely a historical phenomenon but is currently occurring on a recurring basis.
From a conservation standpoint, the study’s conclusions may have significant implications. Hybridization can dilute the local adaptations of polecats and hinder the identification of genetically “pure” individuals, complicating population management and the development of conservation strategies. Additionally, the presence of hybrids may interfere with monitoring programs and the assessment of the species’ conservation status.
“The main risk is not only the occasional existence of hybrids, but that hybridization persists over time and progressively erodes the genetic identity of wild populations and their adaptive capacity,” says Tamara Burgos, lead author of the study.
The study highlights the need to strengthen controls regarding the ownership and release of ferrets, particularly those used for rabbit hunting, which are often lost or abandoned in the wild, as well as to incorporate genetic tools into polecat monitoring programs. The authors emphasize that understanding the true extent of hybridization is essential to ensure the long-term conservation of this little-known carnivore in Iberian ecosystems.
The research was carried out by scientists from the University of Cádiz, Rey Juan Carlos University, Complutense University of Madrid, the National Museum of Natural Sciences in Madrid (Spain), and the University of Aveiro (Portugal), with the participation of more than 80 volunteers in the citizen science project.
Reference:
Burgos, T., Virgós, E., Carmona, G., Martin-Garcia, S., Hernández-Hérnandez, J., Bandeira, V., Quiles, P., Palacín, C., Martín, C.A., Barrientos, R. and Horreo, J.L. (2026). High rates of hybridization between European polecats and domestic ferrets across the Iberian Peninsula. Mammalian Biology. DOI: https://doi.org/10.1007/s42991-026-00573-8
@ Photo by Guillermo Carmona