Elevated Body Temperature Associated with Ketamine Combinations during Capture of Gray Wolves (Canis lupus) in Idaho, USA.

Abstract

Capture and handling of wildlife is essential to answering pertinent questions about ecology and biology. It is important to refine methods to increase animal welfare and safety. Gray wolves (Canis lupus) have been captured annually in Idaho, USA, for management or research purposes since their reintroduction in 1995-96. Two wolves died of hyperthermia during aerial darting in 2015. A retrospective analysis of 490 captures between 1999 and 2018 was conducted to identify factors that might contribute to the likelihood of hyperthermia (body temperature ≥41 C) when using anesthetic drugs in wolves. Wolves were captured in summer (May-October, n=321) by using foothold traps and anesthetized with ketamine-xylazine (n=66), ketamine-medetomidine (n=51), or tiletamine-zolazepam (n=204). Wolves were captured in winter (November-April, n=169) by using aerial darting with ketamine-medetomidine (n=75) or tiletamine-zolazepam (n=94). Mean body temperatures of wolves captured in summer were 39.7 C for ketamine-xylazine, 39.9 C for ketamine-medetomidine, and 39.5 C for tiletamine-zolazepam; in winter, mean temperatures were 40.4 C for ketamine-medetomidine and 39.1 C for tiletamine-zolazepam. In summer captures, hyperthermia occurred in 6/66 (9.1%) of wolves by using ketamine-xylazine, 7/51 (13.7%) by using ketamine-medetomidine, and 19/204 (9.3%) by using tiletamine-zolazepam. For winter captures, hyperthermia occurred in 20/75 (26.7%) of wolves by using ketamine-medetomidine and 7/94 (7.5%) by using tiletamine-zolazepam. Mixed-effects linear regression analysis was used to investigate the role of drug administration on initial body temperature while controlling for demographic and environmental factors. The top models supported effects of drugs administered on initial body temperature for wolves captured in both summer and winter. Ketamine, especially when combined with medetomidine, was associated with greater increased body temperatures than tiletamine-zolazepam, irrespective of season or method of capture.