THE EFFECT OF REARING METHODS ON SURVIVAL OF REINTRODUCED BLACK-FOOTED FERRETS

We estimated minimum survival rates for 282 young-of-year, captive-rea red, black-footed ferrets (Mustela nigripes) reintroduced into prairie dog (Cynomys spp.) colonies in Wyoming, Montana, and South Dakota. We used night surveys with spotlights to locale ferrets about 1 month an d 9 months postrelease. We modeled minimum survival rates using gender , year, site, and 4 rearing methods. Minimum survival rates were highe st (30% for 1 month, 20% for 9 months) for ferrets reared from early a ges in outdoor pens with simulated prairie dog habitat; survival was l owest for cage-reared ferrets released without pen experience (11% for 1 month, 2% for 9 months), Rearing method and year influenced 1-month survival in a comparison of 3 levels of pen experience (pen rearing a s defined above. transfer of kits from toes to pen facilities at age 6 0-90 da)rs, transfer at ape >90 days) during releases in 1994-95 in Mo ntana. Higher survival was associated with intensive management of coy otes (Canis latrans) in 1995. Survival was not different (P > 0.05) be tween sites or sexes, regardless of model. We recommend routine use of outdoor pens for prerelease conditioning of black-footed ferret kits.