No abstract

Cetaceans are remarkable for exhibiting group-specific behavioral traditions or cultures in several behavioral domains (e.g., calls, behavioral tactics), and the question of whether they can be acquired socially, for example through imitative processes, remains open. Here we used a “Do as other does” paradigm to experimentally study the ability of a beluga to imitate familiar intransitive (body-oriented) actions demonstrated by a conspecific. The participant was first trained to copy three familiar behaviors on command (training phase) and then was tested for her ability to generalize the learned “Do as the other does” command to a different set of three familiar behaviors (testing phase). We found that the beluga (1) was capable of learning the copy command signal “Do what-the-other-does”; (2) exhibited high matching accuracy for trained behaviors (mean = 84% of correct performance) after making the first successful copy on command; (3) copied successfully the new set of three familiar generalization behaviors that were untrained to the copy command (range of first copy = 12 to 35 trials); and (4) deployed a high level of matching accuracy (mean = 83%) after making the first copy of an untrained behavior on command. This is the first evidence of contextual imitation of intransitive (body-oriented) movements in the beluga and adds to the reported findings on production imitation of sounds in this species and production imitation of sounds and motor actions in several cetaceans, especially dolphins and killer whales. Collectively these findings highlight the notion that cetaceans have a natural propensity at skillfully and proficiently matching the sounds and body movements demonstrated by conspecifics, a fitness-enhancing propensity in the context of cooperative hunting and anti-predatory defense tactics, and of alliance formation strategies that have been documented in these species’ natural habitats. Future work should determine if the beluga can also imitate novel motor actions.

The Ligurian-Corsican-Provençal Basin is a fin whale summer feeding ground, but little is known about the seasonal movement patterns of this population. We acoustically monitored two regions off Spain (eastern and southern) during summer-fall-winter 2006 using seafloor autonomous recording units. Long patterned sequences of 20 Hz pulses and back-beats from Mediterranean fin whales were identified in both study regions using acoustic features as indicators of population identity. Eastern area: fin whale sounds were detected at very high rates (122 pulses/hour) and between 40-80% of time/day. The detection pattern can be explained by whales moving gradually through the acoustic recorder's detection area, suggesting that the area is probably used as a passage between summer and winter grounds. Southern area: detections from the same population were less abundant (21 pulses/hour) and between 10-35 % of time/day. The detection pattern shows a highly variable distribution with no clear trend, suggesting that Mediterranean fin whales continuously remained in and moved out of the detection area of the recorder from November to January. These results show that this southern area is potentially used as a winter ground. This work documents a new dispersion path towards the Alboran sea, a new potential winter ground.

No abstract

Although much variation exists in jaw morphology among species, odontocetes are believed to receive sound primarily through the pan bone region of the lower jaw. In order to further examine this jaw hearing hypothesis, we tested the head receiving sensitivity and directional hearing of a beluga whale, Delphinapterus leucas. Hearing measurements were conducted with a 9-yr-old female beluga using the auditory evoked potential technique. A preliminary audiogram indicated that the subject had very sensitive hearing (45-55dB from 32-80 kHz) and heard up to 128 kHz. The pathway investigation used a piezo-electric transducer to present the click stimuli, whereas the hearing directivity was measured in the far field, also using broadband clicks. Like the bottlenose dolphin, the subject had a region of high sensitivity around the pan bone region (78 dB), however, unlike the bottlenose dolphin, we found that the region of maximum sensitivity was at the tip of the lower jaw (75dB). The subject also proved to have highly directional hearing. This study supports the shaded receiver hypothesis and also shows that hearing pathway variations appear to exist among odontocete species and are at least partially dependent on head morphology.