Field Anesthesia of South American Sea Lions (Otaria byronia) in Peru Using Medetomidine, Midazolam, and Butorphanol
American Association of Zoo Veterinarians Conference 2019
Michael J. Adkesson1, DVM, DACZM, DECZM (Zoo Health Management); Sathya K. Chinnadurai1, DVM, MS, DACZM, DACVAA, DACAW; Julie A. Balko2, VMD, DACVAA; Gwen Jankowski3, DVM, MS, DACZM; Jenny M. Meegan4, DVM, DACZM; Susana Cardenas-Alayza5, MSc; Matthew C. Allender6, DVM, MS, PhD, DACZM

1Brookfield Zoo, Chicago Zoological Society, Brookfield, IL, USA; 2College of Veterinary Medicine, Department of Molecular and Biomedical Sciences, North Carolina State University, Raleigh, NC, USA; 3Denver Zoo, Denver, CO, USA; 4National Marine Mammal Foundation, San Diego, CA, USA; 5Programa Punta San Juan, Centro para Sostenibilidad Ambiental, Universidad Peruana Cayetano Heredia, Lima, Peru; 6Wildlife Epidemiology Laboratory, College of Veterinary Medicine, University of Illinois, Urbana, IL, USA


Effective conservation program design must include comprehensive information on ecosystem health. As such, conservation efforts at the Punta San Juan (PSJ) marine protected area in Peru include projects assessing population health of the regionally threatened South American sea lion (SASL; Otaria byronia). Such evaluation of free-ranging pinnipeds requires careful field anesthesia in close proximity to water, where suboptimal induction characteristics can result in drowning. Since 2011, 62 SASL (39 male [174.4±38.7 kg], 23 female [82.7±11.3 kg]) have been safely anesthetized with a fixed ratio combination of medetomidine, midazolam, and butorphanol (MMB, 0.053±0.012 mg/kg, 0.31±0.08 mg/kg, and 0.31±0.08 mg/kg, respectively) delivered intramuscularly via dart. Animals were darted while sleeping alone or in small cohorts (males) and in the middle of the rookery during the peak breeding season (females). Biological sample collection (blood, blubber, tooth, gastric contents, urine, and others), flipper identification tags, and satellite tag placement was possible in all animals. Isoflurane supplementation was used in 13 animals primarily to extend anesthetic duration (started at 49.4±18.8 min for 19.3±14.2 min duration). Animals were intubated and provided with ventilatory support as needed to reduce hypercapnia. Physiologic parameters (HR, RR, temperature, SpO2, ETCO2) were carefully monitored. Atipamezole (0.16±0.05 mg/kg), naltrexone (0.27±0.07 mg/kg), and flumazenil (0.0035±0.004 mg/kg) were administered as antagonists 79±24 min following darting. Animals displayed coordinated movement 16±13 min following administration. Recoveries were consistently rated as smooth and uneventful.


The authors thank Marco Cardeña, the biologist teams at the Punta San Juan Program, and all those who have assisted with pinniped health assessment projects. Funding for this project was provided in part by the generous support of the Chicago Board of Trade Endangered Species Fund, the Paul M. Angell Family Foundation, and the Feay Family. We acknowledge the Peruvian government agencies SERNANP for access inside the RNSIIPG-Punta San Juan reserve and AGRORURAL for use of field facilities. Research and samples were collected under permits RJ No. 23-2011, 024-2014, 229-2015-, and 019-2016-SERNANP-RNSIIPG.


Speaker Information
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Michael J. Adkesson, DVM, DACZM, DECZM (Zoo Health Management)
Brookfield Zoo
Chicago Zoological Society
Brookfield, IL, USA

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