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Abstract
Physiological studies involving the use of isotopic water required chemical restraint of free-ranging walruses (Odobenus rosmarus) for several hours. In August 2000, six male walrus (total body mass: 1050–1550 kg) were immobilized in East Greenland by remote delivery of 8.0–9.8 mg of etorphine and subsequently restrained for up to 6.75 h by administration of medetomidine. The effects of etorphine were reversed with 10–24 mg diprenorphine. After termination of the etorphine-induced apnoea, lasting an average of 15.8 min (SD = 9.7, range = 9.5–35.2 min, n = 6), the animals were initially given 10–20 mg medetomidine intramuscularly. The initial dose was further augmented by 5 mg at intervals of 5 min. In two cases, when medetomidine was administered through a catheter inserted in the extradural vein, the animal became instantly apnoeic and regained respiratory function only after intravenous injection of the prescribed dose of the antagonist atipamezole and of the respiratory stimulant doxapram. After an average of 3.5 hours of immobilisation, rectal temperature began to increase and it is conceivable that this is the factor that will ultimately limit the duration of immobilisation. The animals became conscious and fully mobile shortly after an intravenous injection of a dose of atipamezole approximately twice the mass of the total dose of medetomidine given during the procedure followed by 400 mg of doxapram. It is concluded that medetomidine appears to be a suitable drug for chemical restraint of walruses for time-consuming procedures following initial immobilisation by etorphine. With animals of total body mass around 1,000–1,500 kg, the drug should be given intramuscularly in 10–20 mg increments (total mass 10–60 mg) until the breathing rate falls to approximately 1 min-1. At this level, breathing is maintained and animals do not respond to touch or injection.
Highlights
A variety of drugs or drug combinations has to date been used to immobilize walruses (Odobenus rosmarus) in the field, including phencyclidine and acepromazine (DeMaster et al 1981), tiletamine and zolazepam (Stirling and Sjare 1988; Hills 1992; Griffiths et al 1993), etorphine (Hills 1992; Born and Knutsen 1992; Griffiths et al 1993; Acquarone et al 2014) and carfentanil (Hills 1992; Lanthier et al 1999)
Total body mass (TBM) was measured for one animal (Walrus 2) or estimated from measurements of standard body length and axillary girth using the equations in Born et al (2003) and ranged from 1,050 to 1,550 kg
Walrus 1 received 9.8 mg etorphine that was reversed with 14.4 mg diprenorphine (Table 1)
Summary
A variety of drugs or drug combinations has to date been used to immobilize walruses (Odobenus rosmarus) in the field, including phencyclidine and acepromazine (DeMaster et al 1981), tiletamine and zolazepam (Stirling and Sjare 1988; Hills 1992; Griffiths et al 1993), etorphine (Hills 1992; Born and Knutsen 1992; Griffiths et al 1993; Acquarone et al 2014) and carfentanil (Hills 1992; Lanthier et al 1999). To keep control over the animal, a combined dose of 80 mg medetomidine and 1000 mg ketamine was administered, before complete recovery, and provided restraint for further 5 h (Lydersen et al 1992). An investigation of body water dynamics and energy expenditure in walruses in Greenland using isotope labelled water (Acquarone et al 2006; Acquarone and Born 2007) created the need to regularly
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