Inhalant anesthesia for minimally invasive procedures in free-ranging Guadalupe fur seals (Arctocephalus philippii townsendi)

Free-ranging otariids are routinely captured for data and sample collection. To achieve this, anesthesia may be used to facilitate handling, decrease stress, and improve human and animal safety. Injectable anesthetics are widely used for such endeavors; however, certain disadvantages to this approach warrant further exploration of alternative anesthetic techniques. Inhalant anesthesia, commonly utilized for otariids in a clinical setting, is used more sparingly in the field, with few studies assessing safety and efficacy in free-ranging otariids. During 2016–2020, 175 Guadalupe fur seals were net-captured and anesthetized with isoflurane and oxygen on Guadalupe Island, Mexico, for satellite telemetry attachment and biological sampling. To contribute to the body of knowledge surrounding the use of inhalants in the field, physiologic and anesthetic parameters (time to induction, total oxygen use, heart rate, respiratory rate, time to recovery, and anesthetic depth) were assessed for effects of biometric and logistical factors (pursuit and holding time, sex, age class, body weight, year, oxygen flow rate, and total anesthesia time). This anesthetic technique provided rapid induction and recovery times and rare side effects in Guadalupe fur seals, serving as a practical means of field immobilization for minimally invasive procedures in this imperiled species.