Abstract

Two hundred and seventy-six wood bison (Bison bison athabascae) were captured in March of 1997 and 1998 to determine tuberculosis (Mycobacterium bovis) and brucellosis (Brucella abortus) status in Wood Buffalo National Park, Alberta, Canada. Adult males were immobilized by helicopter darting with 7.2±2.6 µg/kg carfentanil (Wildnil, Wildlife Pharmaceuticals, Fort Collins, CO, 3 mg/ml) and 87.6±30.1 µg/kg of xylazine hydrochloride (Rompun, Bayer Inc., Etobicoke, ON, Canada). Mean induction time was 8.7±6.1 minutes and mean reversal time (from anaesthetized to standing) was 6.3±2.3 minutes using a single IM injection of naltrexone hydrochloride (Wildlife Pharmaceuticals, Fort Collins, CO, USA) at a ratio of 132±23 mg naltrexone per mg carfentanil. Induction time was strongly related to darting site, with most rapid inductions occurring with darts into large muscle masses. No cases of renarcotization were observed and all bison appeared clinically normal three days after the first capture.

Adult female and juvenile bison were captured by helicopter net gunning and held in 3×3-m steel pens covered with polyurethane tarpaulins for 72 hours. Short-term tranquilization was achieved with 0.053±0.015 mg/kg intravenous azaperone hydrochloride (Stresnil, Janssen Pharmaceutica Inc., Mississauga, ON, Canada) and medium-term tranquilization with 0.61±0.20 mg/kg IM zuclopenthixol acetate (Clopixol-Acuphase, Lundbeck Inc., Montreal, QC, Canada). A significantly higher (p<0.05) dose of 0.74±0.21 mg/kg was used initially in the first field season, but a lower dose of 0.50±0.099 was tried in 1998 due to the sedative effects observed after release from the pens. Eleven animals were intentionally not given the LAN in 1997, and a marked increase in excitability in the pens was observed compared with treated animals.

Three days after initial capture and processing, penned animals were immobilized with 4.4±1.8 µg/kg carfentanil and 58.5±28.4 µg/kg xylazine fired from a dart pistol. Mean induction time was 4.9±3.6 minutes and mean reversal time was 7.5±3.3 minutes with a dose of 155±23.9 mg naltrexone per mg carfentanil. Xylazine reversal was included in 1998 using tolazoline hydrochloride (Tolazine, Lloyd Laboratories, Canada) intravenously at 1.7±0.26 mg/kg. No significant difference (p<0.05) in reversal time was observed between animals receiving tolazoline plus naltrexone versus those receiving naltrexone alone.

Three capture-related mortalities were observed in 1997 and six in 1998. The lower dose of zuclopenthixol in the 1998 season along with deeper snow and warmer ambient temperatures may have contributed to the additional capture related mortality observed in the 1998 season. Carfentanil and xylazine proved to be a very effective and safe immobilization regime for both free-ranging and penned bison at the doses used, resulting in very good muscle relaxation and minimal side effects. The most common side effects observed were regurgitation and vocalization. Tolazoline commonly produced muscle fasciculations and increased gastrointestinal motility. Zuclopenthixol in conjunction with azaperone seems to be a very effective calming regime for wood bison used at 0.7 mg/kg, with duration of tranquilization varying between two and four days.