Return of Sound Production as a Biomarker of Bottlenose Dolphin Emergence from Anesthesia.

(1) Background: When a human or animal is recovering from general anesthesia, their medical team uses several behavioral and physiological parameters to assess their emergence from the unconscious state to complete wakefulness. However, the return of auditory and acoustic behaviors indicative of the complete return of consciousness in humans can be difficult to assess in a completely aquatic non-human mammal. Dolphins produce sound using the nasal system while using both passive auditory and active biological sonar (echolocation) to navigate and interrogate their environment. The sounds generated by dolphins, such as whistles and clicks, however, can be difficult to hear when the animal is submerged. (2) Methods: We implemented a system to audibly and visually (i.e., using spectrograms) monitor the underwater acoustic behavior of dolphins recovering from anesthesia. (3) Results: Eleven of the twelve recorded dolphins began echolocating within 92 min (Mean = 00:43:41 HH:MM:SS) following spontaneous respirations. In all cases, the dolphins echolocated prior to whistling (Mean = 04:57:47). The return of echolocation was significantly correlated to the return of the righting reflex (Mean = 1:13:44), a commonly used behavioral indicator of dolphin emergence. (4) Conclusions: We suggest that acoustic monitoring for the onset of click production may be a useful supplement to the established medical and behavioral biomarkers of restoring consciousness following anesthesia in bottlenose dolphins.

Acoustic Monitoring of Professionally Managed Marine Mammals for Health and Welfare Insights.

Research evaluating marine mammal welfare and opportunities for advancements in the care of species housed in a professional facility have rapidly increased in the past decade. While topics, such as comfortable housing, adequate social opportunities, stimulating enrichment, and a high standard of medical care, have continued to receive attention from managers and scientists, there is a lack of established acoustic consideration for monitoring the welfare of these animals. Marine mammals rely on sound production and reception for navigation and communication. Regulations governing anthropogenic sound production in our oceans have been put in place by many countries around the world, largely based on the results of research with managed and trained animals, due to the potential negative impacts that unrestricted noise can have on marine mammals. However, there has not been an established best practice for the acoustic welfare monitoring of marine mammals in professional care. By monitoring animal hearing and vocal behavior, a more holistic view of animal welfare can be achieved through the early detection of anthropogenic sound sources, the acoustic behavior of the animals, and even the features of the calls. In this review, the practice of monitoring cetacean acoustic welfare through behavioral hearing tests and auditory evoked potentials (AEPs), passive acoustic monitoring, such as the Welfare Acoustic Monitoring System (WAMS), as well as ideas for using advanced technologies for utilizing vocal biomarkers of health are introduced and reviewed as opportunities for integration into marine mammal welfare plans.

Five members of a mixed-sex group of bottlenose dolphins share a stereotyped whistle contour in addition to maintaining their individually distinctive signature whistles.

Most commonly, animal communication systems are driven by shared call repertoires, with some individual distinctiveness encoded as a byproduct of voice cues. We provide evidence that bottlenose dolphins produce both individually distinctive whistles, and a shared whistle type. A stereotyped whistle contour (termed the group whistle) is shared by five bottlenose dolphins that have lived, worked, and traveled together for at least 21 years. These five dolphins are members of a group of eight dolphins that work as a specialized team for the Navy Marine Mammal Program. Each dolphin is routinely recorded during periods when an individual is isolated from the others in above ground pools as part of their routine training. Each of the eight dolphins has an individually distinctive signature whistle. In addition, at least five of these dolphins share a distinct non-signature whistle type. This shared whistle contour was produced an average of 22.4% +/- 9.0% of the time during periods in which individuals were isolated. During these isolations the signature whistle was produced an average of 42.9% +/- 11.9% of the time. This is consistent with decades of signature whistle research. A group of 10 naïve observers rated the similarity of the different whistle contours. The observers rated the group whistle contour produced by all five dolphins as highly similar (P < 0.01). Their ratings further showed that the signature whistles of the five dolphins were very different (P < 0.01). These findings were further supported by discriminant function analyses. That said, the shared whistle contours still exhibited individual differences which may allow conspecifics to identify the producer even when a whistle contour is shared among multiple dolphins. This is the first in-depth analysis of a non-signature whistle type shared among multiple conspecifics.

Acoustic behavior associated with cooperative task success in bottlenose dolphins (Tursiops truncatus).

Although many species have proven capable of cooperating to achieve common goals, the role of communication in cooperation has received relatively little attention. Analysis of communication between partners is vital in determining whether actions are truly cooperative rather than serendipitous or learned via trial and error (Chalmeau and Gallo in Behav Process 35:101-111, 1996a. doi: 10.1016/0376-6357(95)00049-6 , Primates 37:39-47, 1996b. doi: 10.1007/BF02382918 ). Wild cetaceans often produce sounds during cooperative foraging, playing, and mating, but the role of these sounds in cooperative events is largely unknown. Here, we investigated acoustic communication between two male bottlenose dolphins while they cooperatively opened a container (Kuczaj et al. in Anim Cogn 18:543-550, 2015b. doi: 10.1007/s10071-014-0822-4 ). Analyses of whistles, burst pulses, and bi-phonations that occurred during four contexts (i.e., no container, no animals interacting with container, one animal interacting with container, and two animals interacting with container) revealed that overall sound production rate significantly increased during container interactions. Sound production rates were also significantly higher during cooperative successes than solo successes, suggesting that the coordination of efforts rather than the apparatus itself was responsible for the phonation increase. The most common sound type during cooperative successes was burst pulse signals, similar to past recordings of cooperative events in bottlenose dolphins (Bastian in Animal sonar systems. Laboratoire de Physiologie Acoustique, Jouy-en Josas, pp 803-873, 1967; Connor and Smolker 1996).

Underwater observations of dolphin reactions to a distressed conspecific.

This report describes the epimeletic (or "caregiving") behavior produced by members of a group of Atlantic bottlenose dolphins (Tursiops truncatus) and the possible role of the ailing animal's distress call in eliciting such behavior. Epimeletic behavior in cetaceans most typically involves forms of support provided to a distressed, injured, or dying animal (Caldwell & Caldwell, 1966). Analyses of underwater video and corresponding acoustic recordings revealed a distressed dolphin (the DD) that frequently produced what are most likely distress calls, often paired with the emission of long bubble streams. The frequency of her whistle production was positively correlated with the frequency of the supporting behaviors the DD received from other dolphins. These helping behaviors included raft formations, lifts, and stimulating pushes that were predominantly directed toward the upper third of the DD's body, all of which appeared to be directed towards bringing the DD toward the surface so that she could breathe. This is the first documented underwater account of multiple wild bottlenose dolphins providing epimeletic care to a distressed conspecific, and highlights the possible role of distress calls in such scenarios.