A Review of Black-Footed Ferret Reintroduction in Northwest Colorado, 2001-2006

BETWEEN THE FALL OF 2001 and the end of 2006, 217 black-footed ferrets (Mustela nigripes) were released within the Wolf Creek Management Area (WCMA) in northwest Colorado in an effort to reestablish this species within its former range. Following 5 years of releases and monitoring, the minimum pre-breeding (spring) population within the WCMA in 2006 was 9 ferrets and the minimum population at the end of 2006 was 13 ferrets. While survival of released captive-raised ferrets was high for some colonies in the eastern portion of the WCMA, survival throughout much of the rest of the area was low compared to other ferret reintroduction sites. Three wild-born kits from three separate litters were documented, representing a major step in the recovery effort. However, the observed average litter size of 1.0 was also lower than other reintroduction sites and is probably insufficient to maintain the population without yearly supplemental releases. Overall minimum ferret population size in the WCMA increased steadily from 2002 to 2006, as did the population of their primary prey, the white-tailed prairie dog (Cynomys leucurus). Observed differences in ferret survival and numbers of wild-born kits produced in different portions of the WCMA appear to be driven primarily by differences in habitat quality (the density of prairie dogs and their burrows). This reintroduction program has contributed valuable information for research and management needs pertinent to ferret recovery range-wide, and work continues toward the establishment of a viable population and recovery of this species in Colorado