Surgically implanting river otters with intra-abdominal radiotransmitters using reversible non DEA-scheduled drugs

River otters (Lontra canadensis) are typically implanted with internal intra-abdominal transmitters for research purposes as they are ill-suited for traditional radiocollars. The additional requirements of surgery compared to other types of radiomarking may limit important areas of research for river otters. Availably of an approved surgery suite can be locally limited and transport of a river otter to that location from the trapping site increases stress to the animal. Additionally, using scheduled drugs in a field setting can be difficult due to strict U.S. Drug Enforcement Agency regulations as well as additional restrictions often enforced by Institutional Animal Care and Use Committees. To address these issues we developed a successful protocol for immobilizing river otters with non-scheduled drugs and conducted surgery in the field at capture sites in southern Illinois. We surgically implanted 11 river otters with radiotransmitters during November 2018- February 2019 and recorded only 1 surgery-related mortality. Initial sedation was achieved with an intramuscular injection of Dexmedetomidine (0.06 mg/kg) and Nalbuphine (1.2 mg/kg) and maintained with isoflurane (1-4%). A 3x3 m tent was used as a shelter when needed and aseptic technique was maintained throughout all procedures. Penicillin G benzathine (1 mL) and meloxicam (0.5 mL) were administered prior to the first incision and a reversal of atipamezole equal to the dose of dexmedetomidine was given immediately after completion of the surgery. River otters were recovered in a large pet carrier and released as soon as a full recovery was achieved, typically 0.5-1 hr post-surgery. We conclude that this method for radiomarking river otters minimizes stress and handling time without compromising the health of the animals and provides researches with a less restricted source of chemical immobilization.