Dissociative anaesthesia in free-ranging male koalas and selected marsupials in captivity
M BUSH,1 JAM GRAVES,2 SJ O’BRIEN3 and DE WILDT1
1National Zoological Park, Smithsonian Institution, Washington, DC
2Department of Genetics and Human Variation, LaTrobe University, Bundoora, Victoria 3083
3Laboratory of Viral Carcinogenesis, National Cancer Institute, Frederick, Maryland 21701, USA
Forty seven free-ranging, adult, male koalas were captured and administered an intramuscular injection of the dissociative anaesthetic, TeIazoP (tiletamine HCI plus zolazepam HCI), at dose rates of 5.0 to 7.7 mglkg body weight. Anaesthesia induction was rapid and smooth and resulted in a surgical plane of anaesthesia lasting 30 to 45 min. There was no depression of heart rate or respiration. Mild salivation occurred in most animals, but was not a problem because the swallowing reflex was retained. There was no mortality or morbidity and the anaesthesia level was sufficient to allow electroejaculation and multiple blood sampling with no apparent animal discomfort. For 10 of 19 males in which anaesthesia was required for a 90 min protocol, a supplementary Telazol injection (average, 2.5 mg/kg) was necessary. All koalas recovered completely within 3 to 4 h of the initial injection. The results suggest that the optimal Telazol dosage for the adult male koala is 7.0 mg/kg body weight. The retrospective analysis of 259 anaesthesia records involving 14 species indicated that Telazol was equally effective and safe in other captive marsupials.