The use of carfentanil with other drugs to immobilize moose (Alces alces) has yielded mixed results. Previous work on chemically immobilizing moose with these drugs reported mortality of 6–19%. Even the most recent study of free-ranging moose using the same drug combination as we used in this report (carfentanil and xylazine) had 6% mortality within several days of immobilization. Another recent study suggested that carfentanilxylazine produced unsatisfactory results in moose through exacerbated mortality risks induced by xylazine. As part of an ongoing study of carnivore effects on moose populations, we chemically immobilized 48 moose (41 adult females, one immature male, 6 calves) by charge-powered dart. Low-stress techniques were used, including quiet ground stalks by one individual and use of blindfolds and low noise during processing. On our few aerial captures we immediately withdrew the helicopter once the dart was placed and landed during induction. We found that capture-related mortality can be minimized by using effective immobilization dosages that maintain sternal recumbency, by providing naltrexone by intramuscular and subcutaneous routes, by effectively antagonizing xylazine, and by using low-stress techniques. Female moose survival was diminished when body condition was below a threshold, and some mortality occurred, likely due to poor condition per se and not as a direct result of immobilization. We provide a field protocol and drug doses that wildlife managers can use to safely immobilize moose.
