Effects of different doses of medetomidine and tiletamine–zolazepam on the duration of induction and immobilization in free-ranging yearling brown bears (Ursus arctos)

Abstract

We compared anesthetic protocols with different doses of tiletamine–zolazepam (TZ) combined with medetomidine (M) for 288 yearling brown bear ( Ursus arctos L., 1758) immobilizations with the objective of finding a combination of doses that would provide fast induction with a duration of anesthesia long enough to minimize the need for administering additional drug. The duration of induction time and immobilization was dose-dependent. Increasing the M dose resulted in significantly shorter induction times and a lower probability of giving supplemental drugs. Increasing the TZ dose prolonged duration of anesthesia. For yearling brown bears in Scandinavia, captured shortly after den emergence in April and May, we recommend total dart doses of 1.0–1.66 mg M/dart, plus 62.5–125 mg TZ/dart, depending on the individual requirements for the length and depth of anaesthesia.