Field immobilization and use of radiocollars on long-tailed weasels

Using radiocollars to conduct relatively long-term studies of weasels (Must ela spp.) is problematic because individuals shed collars frequently and be cause collars may induce behavioral changes. During 1998-1999, we immobiliz ed 16 free-ranging long-tailed weasels (Mustela frenata) using 25-mg/kg ket amine hydrochloride and 2-mg/kg xylazine hydrochloride. Mean induction time was 2 minutes and time to first arousal averaged 26 minutes. We fitted 9 m ale and 6 female weasels with 6.5-g and 3.2-g tuned-loop radiocollars, resp ectively. Of these, we observed 5 males and 2 females in captivity under se mi-natural conditions. Radiocollars did not appear to influence weasel use of burrows and coarse woody debris or compromise their ability to kill prey . In the field, 8 of 9 males and all females retained collars more than one week. Males were tracked for a mean of 62 days (range=5-158 days), whereas females were tracked for a mean of 51 days (range=8-108 days). Radiocollar s did not appear to adversely affect foraging or reproduction of ragged wea sels.