Immobilization of free-ranging Rocky Mountain Bighorn Sheep, Ovis canadensis canadensis, ewes with Telazol® and xylazine hydrochloride

We determined the efficacy of immobilizing human-habituated, free-ranging Rocky Mountain Bighorn ewes (Ovis canadensis canadensis) with Telazol® and xylazine hydrochloride (HCl) in summer and winter. Eleven sheep were approached from the ground and darted with one of three drug doses between 1995 and 1998. Mean induction time for the winter recommended dose (250:30 Telazol® and xylazine HCl) was 20.4 min (SD = 6.0, range = 14 to 27) and duration of immobilization averaged 78.3 min (SD = 20.2, range = 59 to 99). Mean induction time for the summer recommended dose (370:30 Telazol® and xylazine HCl) was 19 min (SD = 3.6, range = 15 to 22) and the mean duration of immobilization was 56 min (SD = 19.8, range = 42 to 70). Immobilization response times were not different by season, pregnancy status, or lactating state of ewes. When combined with Telazol®, the xylazine HCl dose required for effective immobilization was less than reported in other studies where xylazine HCl was used in combination with other drugs or used alone to immobilize Bighorn Sheep. In this study, 250 mg of Telazol® (4.2 mg/kg) and 30 mg xylazine HCl (0.5 mg/kg) in winter and 370 mg of Telazol® (6.2 mg/kg) and 30 mg of xylazine HCl (0.5 mg/kg) in summer provided effective and safe immobilization of human-habituated, free-ranging Bighorn ewes with minimal side effects.