Abstract:
Immobilization and anaesthesia of adult male
southern elephant seals (Mirounga leonina) is potentially
risky for animals and scientists. A tiletamine/zolazepam
injection is considered the most appropriate drug combination
for field application in this species. Since appropriate
dosages are difficult to assess due to uncertainties in
weight estimation, we used photogrammetry-derived
weight estimates to ensure precise post hoc calculations of
dosages. We report on 15 intramuscular tiletamine/zolazepam
immobilizations of post-moult males of the upper
weight class at King George Island/Isla 25 de Mayo, in
April 2010. Initial injections were made using blowpipe
syringes. Mean tiletamine/zolazepam combined dosages of
0.71 mg kg-1 (SD ± 0.16) ranged between 0.46 and
1.01 mg kg-1. In four cases, ketamine was added in dosages
between 0.96 and 2.61 mg kg-1. Mean induction
period was 23 min (± 15), and the mean duration of the
procedures from first injection to release of the animals
required 96 min (± 51). Four seals exhibited periods of apnoea, and one case of an extended, repetitive, and
potentially critical apnoea ([25 and 8 min) required
intervention in order to successfully re-initiate spontaneous
respiration. All procedures resulted in proper immobilizations
allowing for the deployment of the satellite tags on
the seals’ heads. The fact that even substantial deviations
between the initial weight estimates and the photogrammetry-
derived weight estimates had no apparent effect on
the course of the immobilization underlines the drugs’ wide
safety margin in this species.
