Abstract

When a human or animal is recovering from anaesthesia, their medical team uses a number of behavioural indicators (e.g., opens their eyes, swallows, speaks) in their discharge assessment. The veterinarians at the U.S. Navy’s Marine Mammal Program have historically used the frequency of spontaneous breaths, movement of eyes, return of cranial nerve responses, and response to tactile stimuli to determine when a dolphin was ready to be extubated and placed in shallow water following an anaesthetic procedure. Once the animal was able to maintain buoyancy, remain unassisted in sternal positioning in the water column, and exhibit complex movements of the blowhole, the dolphin was classified as awake, stable, and ready to safely return to its open water enclosure.

Dolphins produce sound using the nasal system that can be difficult to hear when the animal is submerged. We created a system to audibly and visually monitor the underwater acoustic behaviour of dolphins as they recovered post-anaesthesia. Nine out of the ten recorded dolphins began echolocating within 90 minutes (mean = 45 minutes 08 seconds) following extubation. In all of those cases, the dolphins echolocated prior to whistling. On average, animals began whistling 2.5 hrs following extubation (Range = 00:28:57–22:08:08). All dolphins fully recovered from their procedures. We recommend application of this acoustic monitoring system to identify vocal biomarkers of recovery and to supplement the previously utilized behavioural indicators for identifying when a dolphin is awake, recovered, and ready to return to their natural water enclosures.