River otter chemical immobilization and field surgery using nonscheduled drugs

Abstract

Radiotelemetry provides valuable information about wildlife populations that is often unattainable using other methods. Many vertebrate species can carry radiotransmitters on collarsor harnesses, but radiotelemetry can be more problematic for other species. River otters (Lontra canadensis) are typically radiomarked by surgically implanting intra-abdominal transmitters under general anesthesia. However, surgical requirements and restrictions on some immobilizing drugs may limit options for implanting river otters with radiotransmitters in the field.To address these issues, we developed a protocol for chemically immobilizing live-captured river otters with nonscheduled drugs (by estimated weight class; dexmedetomidine 0.06 mg/kg and nalbuphine 1.2 mg/kg) and conducting field surgeries at capture sites. We surgically implanted 23 river otters with radiotransmitters in southern Illinois during November 2018−March 2020. A plane of anesthesia suitable for surgery was maintained with isoflurane (1−4%). After surgery, capture drugs were reversed with atipamezole and river otters were typically released in 30−60 min. We recorded one surgery-related mortality and one post-surgery mortality.Our surgical method for radiomarking river otters minimized stress and handling time without compromising their health and demonstrated the efficacy of less-restricted chemical immobilization agents for river otters.