Immobilization of free-ranging adult male southern elephant seals with Immobilon(tm) (etorphine/acepromacine) and ketamine

Twenty-seven free-ranging adult male southern elephant seals (Mirounga leonina) were immobilized to enable attachment of satellite-linked dive recorders (SLDRs) and to obtain biopsy specimens. Large Animal Immobilon(tm) (LA Immobilon(tm)) was injected remotely to achieve initial sedation (x = 0.0009 mg/kg etorphine; 0.0037 mg/kg acepromacine) while ketamine was injected manually on demand to maintain narcosis (x = 81 min). The total dosages (x = 1.7 mg/kg) of ketamine required were negatively correlated with those of LA Immobilon(tm) (P (tm) (x = 0.0052 mg/kg diprenorphine) injected intravenously (n = 3), intramuscularly (n = 5) or sublingually (n = 1). LA Immobilon(tm) appears to be useful to attain immobilization in free-ranging, adult male southern elephant seals by remote injection owing to its high potency and hence small volume required. It must, however, be used sparingly and ideally only for initial sedation owing to its potential danger and narrow therapeutic margin.