Use of Hyaluronidase to Improve Chemical Immobilization of Free-ranging Polar Bears (Ursus maritimus)

We assessed the efficacy and safety of hyaluronidase to improve chemical immobilization of free-ranging polar bears (Ursus maritimus) captured from helicopter by remote drug delivery along the Ontario coast line of northwestern James Bay and southern Hudson Bay during September 2005 and October 2007. We used a single blind study design in which one person prepared and loaded all darts without the shooter knowing whether hyaluronidase (150 IU per dart) or sterile water was added to the immobilizing drug mixture of xylazine and zolazepam-tiletamine (XZT). We found that we often required more than one dart to immobilize bears in the control group (XZT+sterile water; >1 dart for 15 of 28 captures) versus the treatment group (XZT+hyaluronidase; >1 dart for seven of 26 captures). As a consequence, treatment bears were generally immobilized with smaller XZT dosages (7.9 vs. 9.4 mg/kg; P=0.08) and shorter induction (10 vs. 15 min; P=0.004) than control bears. We found no differences in vital rates and serum biochemistry results between control and treatment bears. We did find, however, that induction times correlated directly with rectal temperature at ≤15 min after immobilization (r=0.39, P=0.004), which suggests that use of hyaluronidase also helped prevent development of high body temperature (hyperthermia) in polar bears. Overall we found hyaluronidase to be effective and safe for capture of polar bears. We recommend further study to determine whether effects of hyaluronidase are dose dependent and recommend that others involved with capture of seasonally fat species such as polar bears consider use of hyaluronidase to improve chemical immobilization.