Black-footed Ferret - Evolution

Evolution

Like its close cousin, the Asian steppe polecat (with which it was once thought to be conspecific), the black-footed ferret represents a more progressive form than the European polecat in the direction of carnivory. The black-footed ferret's most likely ancestor was Mustela stromeri (from which the European and steppe polecat are also derived), which originated in Europe during the Middle Pleistocene. Molecular evidence indicates that the steppe polecat and black-footed ferret diverged from Mustela stromeri sometime between 500,000 and 2,000,000 years ago, perhaps in Beringia. The species appeared in the Great Basin and the Rockies by 750,000 years ago. The oldest recorded fossil find originates from Cathedral Cave, White Pine County, Nevada, and dates back to 750,000–850,000 years ago. Prairie dog fossils have been found in six sites where ferrets are yielded, thus indicating that the association between the two species is an old one. Anecdotal observations and 42% of examined fossil records indicated that any substantial colony of medium- to large-sized colonial ground squirrels, such as Richardson's ground squirrels, may provide a sufficient prey base and a source of burrows for black-footed ferrets. This suggests that the black-footed ferret and prairie dogs did not historically have an obligate predator-prey relationship. The species has likely always been rare, and the modern black-footed ferret represents a relic population. The earliest reported occurrence of the species is from a late Illinoian deposit in Clay County, Nebraska, and is further recorded from Sangamonian deposits in Nebraska and Medicine Hat. Fossils have also been found in Alaska dating from the Pleistocene.