Summary
Elephant seals were immobilized intravenously with a mixture of tiletamine and zolazepam at a rate of 0.5 mg/kg. This provided a satisfactory degree of anaesthesia with no side effects. Induction, duration and recovery times were short which proved advantageous to researchers and animals. The mean dose rate was 0.46 ± 0.07 mg/kg, the induction time was 26 seconds (± 9 seconds) and the mean level of anaesthesia was 4 units on an eight point scale. Male seals were given, less drug than female seals, remained immobilized for shorter periods and recovered sooner. The mean dose of drug administered to males was 0.44 ± 0.06 mg/kg and to females 0.48 ± 0.08 mg/kg, while the mean duration times were 14.5 ± 4.5 minutes and 16 ± 5 minutes respectively. The mean time taken to recover from immobilization was 15.0 ± 4.5 minutes for males and 16.0 ± 5 minutes for females. Physiological condition and size significantly affected the duration of anaesthesia. Thinner animals remained immobilized for longer than did their fatter contemporaries (F(1,594)= 194.15, p< 0.0000). Thin seals remained immobilized for 18 ± 7 minutes while fatter seals remained immobilized for 15 ± 4 minutes. This difference was significant (t(592)=5.31, p=0.0000). Intravenous drug administration provided an effective and safe method for immobilizing seals. Our technique of immobilization may be of general application for phocid seals because of the easy access to the extradural vein and the small volumes of drugs that are used.