Helicopter-Based Chemical Immobilization of Mountain Goats in Coastal Alaska

The development, evaluation, and refinement of effective and humane capture methods for wildlife studies is important for increasing our capacity to understand and effectively manageand conserve wildlife populations. Carfentanil has been the primary agent used to chemically immobilize mountain goats (Oreamnos americanus) during the past 40 years. However, carfentanil is no longer commercially available for wildlife captures in North America. To investigate viable alternatives for mountain goat capture, we conducted field trials using thiafentanil to immobilize free-ranging mountain goats via aerial darting methods; thiafentanil responses were then compared to a standard and widely used carfentanil dose. During June-October, 2005-2020, we immobilized mountain goats with either 2.4-3.0 mg carfentanil (n = 444) or 6.0-7.0 mg thiafentanil (n = 68) across a range of different field conditions at 6 different study sites in coastal Alaska. Induction and recovery times were more rapid (and subsequent immobilization times reduced) using thiafentanil compared to carfentanil. In most other respects, however, immobilization characteristics (i.e., body temperature, pulse rate, relative oxygen saturation) were virtually indistinguishable between individuals immobilized with carfentanil or thiafentanil. During typical immobilizations, mean rectal temperature increased 1.8 degrees C, but increased as much as 3.0 degrees C in some extreme cases. Administration of supplemental oxygen resulted in substantial, potentially clinically significant increases in peripheral capillary oxygen saturation, arterial oxygen, and pH in immobilized mountain goats. Our findings indicate that thiafentanil is an effective alternative to carfentanil for chemical immobilization of mountain goats and may offer some important advantages, particularly when immobilizing mountain goats and other species in difficult and potentially dangerous capture environments. (c) 2021 The Wildlife Society.