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.