Two litters of black-footed ferrets born this week boosts the number of weasel-like mammals in a captive breeding program to 38 and raises the hopes of researchers trying to save the species from extinction.

The first litter of four ferrets, or kits, was delivered Tuesday night by 2-year-old mother Jezabelle at the Wyoming Game and Fish Department's Sybille Wildlife Research Center, said department spokesman Larry Kruckenberg.

The second litter of three was delivered Wednesday by Collene, Jezabelle's 2-year-old sister, said Kruckenberg.

The captive breeding program started with 18 black-footed ferrets captured in late 1985 and early 1986 in northwest Wyoming from the only wild colony of the animal known to exist in the world.