The anaesthesia of free-ranging male sea lions in a shoreline environment
presents many challenges. The size and physical strength of adult male sea
lions precludes induction via face mask and their tendency to haul out and
remain close to the water line necessitates careful selection of individuals
and thorough planning to mitigate the risk of darted animals returning to the
water while becoming anaesthetised.
The Department of Parks and Wildlife (DPaW), the Department of Fisheries and Perth Zoo undertook a collaborative project to anaesthetize free-ranging adult male Australian Sea Lions (Neophoca cinerea) at Carnac Island, Western Australia, to facilitate fitting of satellite tracking devices to determine their feeding and activity patterns. Four sea lions were anaesthetised during two field trips in October and November 2009.
Body weights of sea lions were estimated by wildlife rangers from DPaW to be in the body weight range of 150-180kg. Sea lions were anaesthetised with tiletamine-zolazepam (Zoletil®) at an estimated dose rate of 1-1.1mg/kg. Three of the sea lions were intubated and maintained on isoflurane after induction; the fourth animal roused itself during supplementary mask induction with isoflurane, before it could be intubated, so the procedure was discontinued. This animal was monitored for several hours after darting, both in and out of the water.
Of the three animals fitted with tracking devices, two lost their devices naturally. The third was anaesthetised again five weeks later, using the same anaesthetic protocol, for removal of the device.
Careful planning, consultation with groups undertaking similar studies and engagement of personnel experienced in sea lion biology, ecology and anaesthesia were important factors in the success of the procedures.