Abstract: The recent development of potent and specifica lphar-adrenoceptoar gonistsa nd antagonists has enhanced their use in nondomestic animal immobilization and reversal. Medetomidine, a new potent alphar-agonist, in combination with the dissociative anesthetic ketamine, has been used to immobilize a variety of nondomestic mammals. Medetomidine alone induces sedation in a dose-dependent way, and complete immobilization has been achieved with high doses in semidomesticated reindeer (Rangifer tarandus) and blue foxes (Alopex lagopus). Howbver, we feel that ketamine should be added to the immobilization mixture to ensure complete immobilization and operator safety. In ketamine combinations, medetomidine doses are usually 60-100 pg/kg. The required ketamine doses are remarkably low:0.8-1.6 mglkg in most ruminants,2.5-3.0 mgUgin felids,u rsids,a nd canids,a nd 5.G-8.0m glkgi n primates,w olverines(Gulog ulo),ando therm uitelids. Clinically, the resulting immobilization is characterized by a smooth onset, good to excellent myorelaxation, and areflexia at higher doses. Determinations of hematologic, serum biochemicil, arterial blood gas,a nd acid-bases tatusp arametersi ndicate that the immobilization is physiologically sound. We have had no fatalities attributable to the immobilization mixture ( I ,240 immobilizations). The alphar-adrenoceptora ntagonist,a tipamezole,i s highly efective in reversingt he immobilization induced by medetomidine, medetomidine-ketamine combinations, or xylazine. In ruminants, the medetomidine-ketamine-induced immobilization can be rapidly and persistently reversed by administering 100-l 50 1rg/kg of alipamezole i.v. and the rest s.c., adjusting the total atipamezole dose to an atipamezole: medetomidine ratio of approximately 4-5 (w/w). Becauseth e required ketamine doses are relatively high in carnivores, we prefer to use a lower atipamezole dose (totil atipamezoie: medetomidine ratio approximately 2-3 w/w) and to administer it i.m. or s.c. Using thii regimen, reversals are calm and animals show minimal “residual ketamine effect.” Because atipamezole is a competitive antagonist, its dose should be reduced if it is administered late in the immobilization period when a large part of medetomidine has been endogenously metabolized. Xylazine-induced immobilization is rapidly reversed by I mg of atipamezole for every 8-12 mg of xylazine used.

Abstract: Przewalski's gazelle Procapra przewalskii is endemic to China and is classified as Critically Endangered by IUCN-The World Conservation Union. Historically, the species occurred in parts of the provinces of Gansu, Inner Mongolia, Ningxia and Qinghai but now appears to be restricted to three populations around Qinghai Lake. These three populations-Bird Island, Hudong-Ketu and Yuanzhe-have all declined since 1988. The populations have been monitored since 1994 and the smallest, on Bird Island, appears to be on the brink of extinction, with only seven individuals being recorded in 1998. In the same year, the Hudong- Ketu population comprised 56 individuals (29.4 per cent males, 50 per cent females and 21 per cent juveniles) and the Yuanzhe population 51 individuals (29.4 per cent males, 43.1 per cent females and 27.5 per cent juveniles). The causes of the declines vary for each population but include loss of habitat as a result of desertification, poaching and, possibly, wolf predation. Human activity and high juvenile mortality are major threats to the continued survival of the gazelle. Conservation measures proposed are: (i) the establishment of a special reserve for Przewalski's gazelle; (ii) a study of the wolf-gazelle relationship and control of the number of wolves if necessary; (iii) a search for remnant populations of Przewalski's gazelle in other regions in their historical range and the identification of suitable sites for translocation and establishment of new populations.