Immobilization of southern elephant seals (Mirounga leonina).

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Ramdohr, S. , Bornemann, H. , Plötz, J. and Bester, M. N. (2000): Immobilization of southern elephant seals (Mirounga leonina). , In: Lechner-Doll, M. & Hofer, H. (eds), 3rd International Symposium on Physiology and Ethology of Wild and Zoo animals, Berlin, Advances in Ethology, Supplements to Ethology:149 .
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Studies on wild pinnipeds such as attachment of instruments or samplingof tissue necessarily require immobilization. This is particularly difficult inelephant seals due to their size, variable constitutions, and unpredictableresponses to drugs. Harsh field conditions create additional problems. Fieldmethods for immobilizing juvenile and adult southern elephant seals arepresented.The study was carried out in 1996, 1997, and 2000 at King George Island,Antarctica. We immo-bilized 7 weaned pups (x=147 kg) and 13/21 adultfemales/males (x=310/1613 kg) after their annual moult to enabledeployment of activity recorders or tissue sampling. In pups, ketamine/diazepam (x=7,3/0,3 mg/kg), and in females, ketamine/xylazine(x=10,9/0,4 mg/kg) was used to attain immobilization for about 50-150 min.In males, initial immobilization was achieved with etorphine (x=0,0009 mg/kg),and ketamine was administered on demand (8=1,6 mg/kg total dosage) tomaintain narcosis for 40-170 min. All drugs were injected intramuscularly.In adults, initial dosages were given remotely using self-evacuating syringespropelled with a CO2-powered rifle. All dosages in pups, and follow-updosages in adults were injected manually.In pups and females, the drugs used were found to provide appropriatesedation and anaesthesia. Due to individual response and field conditions,dosages varied considerably. In males, etorphine is presumably the only druguseful to attain immobilization by remote injection due to its high potencyand thereby small volume required. The dosages of etorphine wereapproximately four times lower than recommended for other large-sizedmammal species, and the therapeutic range was low. In seven cases,immobilization needed to be reversed by intravenous or intramuscularinjections of the etorphine antidote diprenorphine (x=0,0045 mg/kg). As aresult, etorphine was used sparingly and simply for sedation to allow closeapproach. Consequently, ketamine could be administered by hand atmarkedly reduced dosages.

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