Helicopter-based immobilization of moose using butorphanol–azaperone–medetomidine

Abstract

Chemical immobilization is an important tool for the capture, study, and management of wildlife. Increased regulation of traditional opioids has necessitated a search for alternative drugs in wildlife capture. Butorphanol–azaperone–medetomidine (BAM) is one promising alternative that has been used in a range of taxa, though often on medium-size mammals using ground-based methods. We tested the efficacy of BAM via remote delivery from a helicopter in a wild population of moose (Alces alces shirasi) in northwestern Wyoming. In March 2020 and 2021, we immobilized male (n = 15) and female (n = 26) moose with butorphanol (0.20 mg/kg), azaperone (0.066 mg/kg), and medetomidine (0.079 mg/kg), with antagonists atipamezole (0.495–0.527 mg/kg) and naltrexone (0.124–0.151 mg/kg) to reverse immobilizations. Mean induction (x̄ ± SE; 9.2 ± 0.6 min) and mean recovery times (7.2 ± 0.5 min) were longer but still comparable to published instances of moose captured using traditional chemical immobilizers (carfentanil, etorphine, thiafentanil). All animals survived >60 days post-capture. Our findings add to a body of work demonstrating that BAM provides rapid inductions, reliable sedation, and quick reversals in a variety of taxa and by aerial remote delivery.