Between 0.75 and 1.08kg. The Black-footed Ferret preys primarily upon Prairie Dogs although mice, voles, ground squirrels and other small animals are also taken. The Black-footed Ferret is nocturnal and lives in the burrows dug by Prairie Dogs. It was also found in the extreme eastern portions of Utah and Arizona. The Black-footed Ferret has declined in direct proportion to the Prairie Dog.
Canine distemper is fatal for Black-footed Ferrets and it has decimated many populations.
As ferrets live at low densities, a breeding population is spread over a large area. As overall habitat becomes more fragmented, the population becomes less able to reproduce. The last known wild population grew steadily from 60 in 1982 to 129 in 1984 as a result of protection. This trend came to an end in the summer of 1985 when canine distemper infected the ferrets and reduced the population to approximately 31. Black-footed Ferret Factsheet.