Unveiling wolf dietary specialization on free ranging horses using forensic genetics and field monitoring

Wolves occasionally specialize on free-ranging horses when they are abundant and alternative prey is scarce, potentially reducing horse productivity, triggering conflicts with owners, and hampering conservation of both species. Yet, ecological and demographic impacts of wolf predation on horses remain poorly understood. We investigated wolf-horse interactions in NW Portugal by combining wolf monitoring, diet analysis, spatial overlap between wolf and horse activity areas, and horse pedigree reconstruction from genetically identified individuals recovered from wolf scat remains, feeding sites and horse faecal samples. Horses comprised 85% and 93% of wolf consumed biomass in 2017 and 2018 respectively, suggesting strong positive selection. Wolf GPS-tracking identified 19 feeding sites, all containing horse remains, with 26% within wolf core areas. Eight predation events were confirmed, affecting foals (12%), juveniles (> 1 year; 38%) and adults (50%). Genetic analyses identified 39 horses from wolf feeding sites and scat remains, 17 of which were assigned to 10 of the 14 families reconstructed from molecular data, revealing high predation impact on both juveniles and adults. These findings provide rare empirical evidence of wolf predation impacts on free-ranging horses and highlight the importance of integrating demographic and genetic approaches to inform conservation and conflict mitigation.