Ferrets have reached nine years of age in captivity, but achieving three or four years of age in the wild is quite an accomplishment. The reduction of ferret numbers to near extinction has increased the threat to the remaining animals. Several animals, including coyotes, golden eagles, great-horned owls, prairie falcons, badgers, bobcats and foxes, are known to take ferrets or are potential predators of ferrets. High predator populations can have a greater impact on a reduced ferret population. Several diseases affect black-footed ferrets, the most serious being canine distemper and sylvatic plague.
Canine distemper is thought always to be fatal to ferrets.
It is spread by other animals that frequent prairie dog towns, including coyotes, badgers and skunks. It was the main cause of the catastrophic losses of ferrets in northwestern Wyoming in 1985 and 1986. Sylvatic plague is the wildlife version of bubonic plague that devastated the human population in Europe in the Middle Ages. Prairie dogs are susceptible to plague, and entire dog towns can be eliminated quickly. Although ferrets were thought to be resistant to the disease, the death of a captive ferret in 1994 to plague it acquired from eating an infected prairie dog is cause for concern.