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The ability to modify the structure and context of vocalizations through learning plays a key role in the social interactions of many species.  The investigation of categorical matching, an aspect of contextual vocal learning, is the first step toward determining how contextual learning plays a role in the use, comprehension, and categorization of sounds in the wild.  To this end, we conducted a study at the Vancouver Aquarium to test the ability of a juvenile female beluga, Qila, to respond to playbacks of two types of in-air beluga calls with vocalizations that matched the category of call played (a scream, which is a vocalization type shaped over time with reinforcement and not part of this species'natural repertoire, and a pulse-train, a natural call category).  We first tested Qila with random sequences of the same version of the two vocalizations with which she had been trained.  Her overall success in matching all playback stimuli was above chance but not statistically so (66%).  She had more difficulty matching screams (54% success) than pulse trains (80% success).  We next played random sequences of six novel pulse-trains and seven novel screams, which Qila had not been trained with.  She responded correctly to the set of novel stimuli of both call types in 64% of the trials, a success rate that did not differ statistically from chance.  Again, she had more difficulty matching screams (55% success), relative to pulse trains (74% success).  These results indicate that Qila successfully matched only pulse trains, the class that is part of this species’ natural repertoire.  Her poor performance on matching screams might be partly explained by a difficulty to perceive categorically a signal that lacks a function in the natural repertoire of belugas.Keywords: categorical matching, contextual learning, vocal learning, categorization, belugas

Contact calls are ubiquitous in social birds and mammals. Belugas are among the most vocal of cetaceans, but the function of their calls is poorly understood. In a previous study we hypothesized that a broad band pulsed call type labeled “Type A,” serves as a contact call between mothers and their calves. Here we examined context-specific use of call types recorded from a captive beluga social group at the Vancouver Aquarium, and found that the Type A call comprised 24% to 97% of the vocalizations during isolation, births, death of a calf, presence of external stressors, and re-union of animals after separation. In contrast it comprised 4.4% of the vocalizations produced during regular sessions. We grouped 2835 Type A calls into five variants, A1 to A5. A discriminant function analysis classified 87% of calls in the same groupings that we assigned them to by ear and visual examination of spectrograms. The variants do not represent individual signatures. One variant, A1, was used by three related individuals: an adult female, her male calf and his juvenile half-sister. Our previous research documented the gradual development of the A1 variant by the male calf, until at 20 months he was producing stereotyped renditions of his mother and sister’s A1. We used our findings to generate testable predictions about the usage of these signals by wild belugas. We verified the existence of signals with the same distinctive features as the contact calls found in captivity in the repertoire of St. Lawrence Estuary herds, and documented their usage by two wild individuals from different populations. In the St. Lawrence, these were emitted by a female calling after a dead-calf. In Hudson Bay, by a temporarily restrained juvenile. We propose that these calls function in nature, a sin captivity, to maintain group cohesion, and that the variants shared by related animals are used for mother-calf recognition.

Aerial photogrammetry has provided increased power for monitoring the health of individuals in the endangered population of Southern Resident killer whales (SRKW, Orcinus orca) in the eastern North Pacific. These data have shown evidence of nutritional stress, with individual growth and body condition correlating with the availability of their primary prey, Chinook salmon (Oncorhynchus tshawytscha). We used drones to derive similar but novel photogrammetry measurements from a sympatric population of mammal‐eating Bigg's killer whales (BKWs) that has been increasing in abundance in recent decades. From 2014 to 2019 we photographed 95 individual BKWs in Canadian waters off Vancouver Island and US waters in the Salish Sea; we estimated asymptotic lengths of 6.4 m for adult females and 7.3 m for adult males, both longer than corresponding length estimates for SRKWs. As a proxy for body condition, we measured head width at a standardized distance behind the blowhole, expressed as proportion of the length between the blowhole and dorsal fin, and estimated that on average, all age/sex classes of BKWs were more robust than corresponding classes of SRKWs. These differences likely reflect divergent adaptive selection in these prey‐specialist ecotypes, but may also partially indicate recent impacts of differential prey availability. [ABSTRACT FROM AUTHOR]

Abstract--From 2001 to 2004 in the eastern Aleutian Islands, Alaska, killer whales (Orcinus orca) were encountered 250 times during 421 days of surveys that covered a total of 22,491 miles. [...]

Fish-eating and mammal-eating killer whales exhibit different patterns of echolocation sounds to locate and catch their prey. Fish-eating resident whales produce sonar clicks 27 times more often than mammal-eating transient killer whales, possibly due to higher probability of warning the prey. The resident whales apply echolocation frequently during foraging while transient whales do not use echolocation frequently during travelling or foraging. Information is most likely shared as echolocation use decreases with the increasing group size of both the resident and transient whales.

Aerial photogrammetry is increasingly being used to evaluate the body condition of free-ranging cetaceans (Christiansen et al., [4], [5]; Durban et al., [8]; Fearnbach et al., [10]; Miller et al., [16]; Perryman & Lynn, [20]). Only high-quality images where the whales were in straight orientation (i.e., no tilt in the body axis) were selected: the white eye patches of killer whales provide very useful visual landmarks for assessing whale orientation. Estimates of the individual departures from these means showed that the greatest changes in body condition were displayed by the three youngest whales, which notably had the poorest body condition in the May sampling periods (Figure). [Extracted from the article]

Unlike terrestrial mammals that have unambiguous aerial sound transmission pathways via the outer ear and tympanum, sound reception pathways in most odontocetes are not well understood. Recent studies have used auditory brainstem response (ABR) measurements to examine sound reception pathways. This study sought to determine how sound source placements, recording electrode arrangements, and ABR peak analyses affect interpretations of sound reception in the harbor porpoise (Phocoena phocoena). Click stimuli were delivered in air from a contact transducer (“jawphone”). Early ABR peaks (representing auditory nerve responses), and later peaks reflecting higher brainstem activity, were analyzed across jawphone and recording electrode positions. Auditory nerve responses were similar for jawphone placements from the ipsilateral posterior mandible to the tip of the rostrum. Later peaks, however, suggested a possible region of highest sensitivity midway between the posterior mandible and the rostrum tip. These findings are generally similar to previous data for porpoises. In contrast to auditory nerve responses that were largest when recorded near the ipsilateral meatus, later ABR peaks were largest when recorded with a contralateral (opposing) electrode. These results provide information on the processes underlying peaks of the ABR, and inform stimulus delivery and ABR recording parameters in odontocete sound reception studies. [ABSTRACT FROM AUTHOR]

Fisheries and Oceans Canada, "Recovery strategy for the Northern and Southern Resident killer whales (Orcinus orca) in Canada", Species at Risk Act Recovery Strategy Series (2018). Canada cannot ignore its biodiversity commitments to pursue growth at the expense of ecosystems. [Extracted from the article]