Denver ? A program to reintroduce black-footed ferrets to the state received a boost earlier this month when biologists spotted at least five of the rare mammals in good health during an annual spotlighting operation at a northwestern Colorado release site.

Scientists caught one of the ferrets, examined it and concluded it appeared to be thriving in a large white-tail prairie dog town near Massadona, some 35 miles southeast of Dinosaur National Monument.