Arctic foxes,Vulpes lagopusliving on Mednyi Island suffered a drastic decline in population size in the late 1970s due to an outbreak of mange epizootic. This dramatic fall in numbers rendered the subspecies endangered, and the concomitant loss of variability resulted in a population bottleneck. Here, we investigate whether differences in cranial morphology between Mednyi Island Arctic foxes and Bering Island Arctic foxes could be attributed to the severe population bottleneck suffered by the Mednyi population in the 1970s. We used morphometric traits as proxies for genetic data to provide estimates of FST. Results show higher FSTestimates for the Mednyi population than for the Bering population, which we interpret as a bottleneck signature. FSTresults also indicate a pattern of divergence between the two populations consistent with random genetic drift. Bottleneck detection is critical for the interpretation of the demographic history of the endangered Mednyi Island Arctic fox, with consequences for conservation management.