Due to a decision to remodel the San Juan de Aragon Zoo in Mexico City, Mexico, the entire animal collection was relocated. Over 500 animals had to be moved from exhibits and relocated to alternative facilities in less than 60 days. The zoo’s collection at the time consisted of a total of 246 mammals, 236 birds, and 18 reptiles. The transfer of birds and reptiles was accomplished by physical means, while physical and/or chemical means were used for the mammals. Close to 50% of the mammals required at least one session of chemical restraint (n=122). The combination of medetomidine-ketamine was the most frequently utilized protocol in the case of carnivores. Members of the Cervidae family were sedated with the combination of an alpha 2-agonist (xylazine or medetomidine) and ketamine. Carfentanil, in combination with xylazine or detomidine, was used in all cases of antelope restraint. The restraint methods, doses utilized, and results of the transfer are reviewed.
The San Juan de Aragon Zoological Park was opened in 1964. It had been built following an outdated menagerie style design plan. Primates and birds were generally kept in small concrete and chain link enclosures or cages, while carnivores and ungulates were kept in fenced pens with concrete floors and deep moats. Animals could be observed by the public from any point around the exhibit. Few animals had adequate hides or indoor shelter. By 1998, the government of Mexico City decided to redesign the zoo in order to improve the animals’ quality of life, as well as to improve services offered to the visiting public. Reconstruction of the zoo was planned to occur in two phases. The initial phase required transferring 500 animals to other facilities over a period of 2 months. Due to the high number of animals to be relocated, a decision was made to move the animals to other zoos in Mexico City for temporary holding. A large group of birds and carnivores were to be sent to the Chapultepec Zoo. Animals with a historic distribution in the Valley of Mexico, such as cougar (Puma concolor), coyote (Canis latrans), white-tailed deer (Odocoileus virginianus), local birds of prey, and several local columbiformes, were to be sent to the Los Coyotes Zoo, a small facility exhibiting regional fauna. After accounting for temporary facilities for the initial groups of animals, a place for almost 266 remaining animals (mostly ungulates, peccaries, and European wild boars) still had to be determined. Facilities were built on zoo grounds as temporary enclosures so construction could occur in the areas of the original exhibits.
Simple physical means were utilized to capture, transport, and relocate all birds and reptiles Iguanas (Iguana iguana and Ctenosaura pectinata) and different species of tortoise were hand caught and transported in kennels. The equipment used consisted of fishing nets, hoop nets, and gloves. During the periods of manual restraint, permanent identification of the animals was ensured by the placement of electronic microchips or metal bands.
Three types of physical restraint were used in the case of mammals. Capture and restraint devices were used in animals that could be overcome by physical means, such as coyote (Canis latrans), Mexican wolf (Canis lupus baileyi), bobcat (Lynx rufus), and Barbary sheep (Ammotragus lervia). Mechanical restraint was preferred in the case of larger animals and required conditioning the animal to enter a squeeze cage or transport crate without human contact. This method was very useful, especially when translocating a pair of leopards (Panthera pardus) with chronic renal disease, and large groups of European wild boar (Sus scrofa), peccaries (Tayassu tajacu and Tayassu pecari), llamas (Lama glama), and guanacos (Lama guanicoe). This procedure also simplified the translocation of three male giraffe (Giraffa camelopardalis). A special transport crate was designed and built for the procedure. The animals became accustomed to confinement in the static crate, and, after a period of time, were coaxed into it for uneventful transport.
Chemical restraint was utilized to transport and relocate the remaining animals that could not be safely restrained and transported by physical means. Each animal undergoing chemical restraint received a full physical exam. Blood samples were collected for diagnostics as well as for baseline serum sample banking.
Three separate anesthetic protocols were evaluated in carnivores. Tiletamine-zolazepam, medetomidine-ketamine, and ketamine-xylazine combinations were tried and compared.
Doses of 0.04-0.09 mg/kg medetomidine were combined with 3 mg/kg of ketamine and produced complete immobilization with excellent relaxation in all cases. A smooth, rapid, and complete recovery followed the injection of atipamezole at 0.160 mg/kg, given half IV and half IM. Subjectively, when tiletamine-zolazepam was administered to jaguar and cougar at doses of more than 6 mg/kg, it seemed to cause respiratory depression and doxopram was administered (1–3 mg/kg IV) to stimulate the animals. Recovery time was prolonged when compared with either of the reversible combinations. In the case of the combination of ketamine and xylazine, quality of the anesthesia was characterized as fair, but the volume of injection was high and several darts were needed for induction. Furthermore, a third of the combined dose had to be given after 45 min in order to extend the session long enough to allow the manipulation of animals in the new enclosure.
In cervids, ketamine combined with xylazine, ketamine combined with detomidine, and tiletamine-zolazepam combined with xylazine were compared. Fallow deer (Dama dama) restrained with doses of 6 mg/kg ketamine and 0.150 mg/kg detomidine had superior sessions than those receiving 6 mg/kg ketamine and 5 mg/kg xylazine, for which a supplementary half dose was necessary to achieve proper immobilization. White-tailed deer (Odocoileus virginianus) restrained with 4.4 mg/kg of tiletamine-zolazepam combined with 2.2 mg/kg of xylazine resulted in sessions with excellent relaxation and good analgesic effects. These were not observed in the other protocols.
Carfentanil (0.024 mg/kg) combined with xylazine (0.07 mg/kg) was selected to chemically restrain a single 850 kg bison (Bison bison). The induction was rapid and smooth, but the time employed to pick up and carry the animal to the temporary holding facility was prolonged. As a result, the animal regurgitated during the procedure and died 4 days later. Standing sedation was performed on an aged yak (Bos grunniens) to allow manipulation into a transport truck. A dose of 0.100 mg/kg of carfentanil was sufficient to allow for manipulation and transport without complications. The combination of carfentanil (3 mg ) and xylazine (30 mg ) provided good quality restraint in waterbuck (Kobus defassa). The time from antagonist injection (100 mg naltrexone administered IV per 1 mg carfentanil) to standing varied, but in most cases animals were ambulatory within 2 min following antagonist administration. Similar results were obtained in wildebeest (Conochaetes taurinus) with 1.6 mg total carfentanil combined with 16 mg total of xylazine. Chemical restraint of nilgai (Boselaphus tragocamelus) was difficult using published doses of carfentanil (3.0 total mg in females and 3.9 total mg in males IM).1,2 The addition of 10, 15, or 20 mg of detomidine to the narcotic improved the quality of restraint. The addition of 20 mg of detomidine seemed an optimum supplement for both males and females, as it increased relaxation and decreased motion, allowing for much smoother inductions and recoveries.
Overall mortality was 1.4% (seven animals). A green parrot (Aratinga holochlora) was the only death in physically restrained animals, while the other six deaths occurred in animals that were chemically restrained. No deaths were recorded in animals mechanically restrained. The bison was one animal that suffered death while chemically restrained. Also, two white-tailed deer died of cervical trauma during darting. The use of green plastic shade cloth over the exhibit’s chain link fence seemed to resolve the matter. Renarcotization was suspected to be the cause of death in one nilgai, although the same protocol was used in seven other animals with no apparent problems.
Two waterbuck (Kobus defassa) died during the move. In one case, that of a 17-day-old calf, a decision was made to sedate the animal with 100 mg of xylazine IM. Following administration, the calf became recumbent within 3 minuntes and respiratory depression ensued. Doxopram and a full dose of antagonist (yohimbine 0.25 mg/kg) were injected IV, but the animal failed to respond. Following a second full dose of antagonist IV, the animal became sternally recumbent, but remained sedated and slowly became further depressed. The animal died 3 hours later. Inability to effectively metabolize the xylazine was suspected to have caused severe depression and death. Finally, a waterbuck was found dead 4 days following capture and restraint. Necropsy revealed chronic pneumonia.
Under the conditions encountered, the decision to perform a minimum of chemical restraint-based translocations was reflected by a relatively low number of fatalities. Reliable physical methods of restraint should be taken into account when transporting large numbers of animals to alternate locations in a short period of time. No deaths were recorded when mechanical restraint was used. In an urban zoological setting, and under similar conditions, mechanical means may be the most favorable method for successful animal transfer.
The authors would like to thank the veterinary and animal husbandry staff of the San Juan de Aragon Zoo for their invaluable help and assistance in the successful transfer of the collection’s animals.
1. Allen, J.L., D.J. Janssen, J.E. Oosterhuis, and T.H. Stanley. 1991. Immobilization of captive non-domestic hoofstock with carfentanil. Proc. Am. Assoc. Zoo Vet. Pp. 343–354.
2. Kreeger, T.J. 1997. Handbook of Wildlife Chemical Immobilization. International Veterinary Services, Inc. Laramie, Wyoming, USA.