Abstract
The stability and health of the Peruvian populations of the South American fur seal (FS; Arctocephalus australis) and South American sea lion (SL; Otaria flavescens) are poorly characterized. Both species experienced catastrophic population declines associated with the 1997–98 El Niño Southern Oscillation (ENSO) event, with concerns of local extinction amplified by recent data indicating the Peruvian FS population represents a distinct species or subspecies.4 The Punta San Juan marine protected area (15°22'S, 75°12'W) protects key rookeries for both species, with population health assessment projects underway there since 2009.
Previous use of tiletamine-zolazepam is reported in both species,2,6but has been associated with unpredictable quality and duration of anesthesia, apnea, and prolonged recovery times3,5. During November 2011, twelve male FS and seven male SL were anesthetized using a combination of medetomidine-butorphanol-midazolam (M-B-Mi) delivered by DaninjectTM dart. To prevent animals fleeing to water, mature male FS (weight range 95–130 kg; mean 116 kg) that were actively defending a breeding territory were darted at close range, while subadult male SL (weight range 100–205 kg; mean 143 kg) were stealthily darted while sleeping. Mean dosages of M-B-Mi (0.053, 0.3, and 0.29 mg/kg respectively in FS; 0.057, 0.31, and 0.31 mg/kg respectively in SL) were slightly higher than previous reports for this combination in pinnipeds.1,5 Initial drug effect in both species was noted at 4 min. Animals were sedate enough to move onto a stretcher at 18 min (FS) and 15 min (SL).
Supplemental isoflurane was required to complete invasive sample collection and tag placement in 10/12 FS. No supplementation was required for the same procedures in any SL. Four FS and three SL were intubated without supplementation. All other FS were intubated after isoflurane supplementation. Anesthesia was subjectively deeper, smoother, and more reliable in the SL than FS; possibly related to the excited nature of the FS when darted compared to the resting SL. Physiologic parameters remained in expected ranges throughout the procedures, except for a mild-moderate hypercapnea in several animals that occurred despite good spontaneous ventilation. Assisted ventilation using a demand valve improved the hypercapnea.
Animals were reversed with atipamezole, naltrexone, and flumazenil intramuscularly (mean dosages of 0.18, 0.29, and 0.001 mg/kg respectively in FS; 0.2, 0.33, 0.0013 mg/kg respectively in SL). Mean time from dart to reversal was 57 min in both species. Mean time from reversal to awareness was 7 min (FS) and 15 min (SL). Recoveries were smooth and uneventful, with most animals showing no sedation 10–20 minutes post-reversal. Overall, this anesthetic protocol was well tolerated in both species with excellent success, but availability of supplemental isoflurane and ventilatory support is strongly recommended to ensure safety.
Acknowledgments
The authors thank all persons involved with this field project, specifically Marco Cardeña, John Pauley, Dr. Matt Allender, Paulo Guerrero, Franco Garcia, Maria Jose Ganoza, and Wendy Flores. A special thanks to Dr. Patricia Majluf for her long-standing commitment to Punta San Juan and support of this project. Funding for this project was generously provided by the Chicago Board of Trade Endangered Species Fund and the Chicago Zoological Society.
References
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