The use of Ketamine-Xylazine and Ketamine-Medetomidine with and without their antagonists Yohimbine and Atipamezole Hydrochloride to immobilize Raccoons (Procyon lotor) in Ontario, Canada

Introduction Field immobilization of wildlife using various chemical immobilizing agents has been well documented (Mech et al. 1965; Bigler and Hoff 1974; Gregg and Olson 1975; Deresienski and Rupprecht 1989; Belant 1991, 2005; Kreeger 1999; Gehrt et al. 2001). The Ministry of Natural Resources and Forestry (MNRF) wildlife research and monitoring section has an ongoing research and management program in response to rabies in multiple terrestrial carnivore species (Rosatte et al. 1993, 2009). This has led to the development of many research projects involving the chemical immobilization of Red Foxes (Vulpes vulpes), Striped Skunks (Mephitis mephitis) and Raccoons (Procyon lotor) using various tranquilizers, sedatives and dissociative anesthetic agents (Rosatte and Allan 2009; Rosatte et al. 2010). Immobilizing agents are necessary to allow safe handling of live-trapped animals to acquire morphological measurements, permit ear-tagging, apply a radio collar or perform minor surgical procedures such as premolar tooth extraction and blood collection. Tooth and blood collection are required to determine bait acceptance and rabies antibody level following oral rabies vaccine delivery to foxes, skunks and raccoons by hand or aircraft (Rosatte et al. 1993, 2010, 2011). Surgical procedures such as tooth and blood extraction require an adequate level of anesthesia, muscle relaxation and pain suppression. Ketamine alone will provide anesthesia, however muscle relaxation is dosage dependent and pain suppression requires the addition of an analgesic (Gregg and Olson 1975; Fuller and Kuehn 1983; Dzialak et al. 2002). Although the analgesic promotes good muscle relaxation and pain suppression it may prolong recovery time (Dzialak et al. 2002). Combining ketamine with a tranquilizer or sedative has been observed to offset the convulsions often observed when using this drug and provide better muscle relaxation and analgesic properties in some wildlife species (Ramsden et al. 1976; Fuller and Kuehn 1983; Seal and Kreeger 1987; Dzialak et al. 2002; Rosatte and Allan 2009). Not all tranquilizers are reversible but recovery time can be reduced by reversing sedatives using alpha-2 antagonists. Improvements in recovery time have been observed after administering yohimbine hydrochloride to reverse the effects of xylazine in Mule Deer (Odocoileus hemionus), White-tailed Deer (Odo coileus virginianus), Elk (Cervus elaphus), Polar Bears (Ursus maritimus) and Raccoons (Jessup et al. 1983; Mech et al. 1985; Ramsay et al. 1985; Deresienski and Rupprecht 1989; Rosatte 2007). Ideally, field operations require the safe release of animals following immediate recovery from anesthetic, hence, the need for a drug combination that immobilizes animals safely and re duces recovery time. Medetomidine hydrochloride is an alpha-2 agonist that is more potent and 10 times more selective than xylazine hydrochloride; it actively attaches to sites at a ratio of 1620:1 compared with 160:1 for xylazine (SinThe use of Ketamine-Xylazine and Ketamine-Medetomidine with and without their antagonists Yohimbine and Atipamezole Hydrochloride to immobilize Raccoons (Procyon lotor) in Ontario, Canada