Hello,
On behalf of my co-authors, I’m excited to share our new open-access article on the deep-sea behavior of sub-adult male northern elephant seals. The study delves into their feeding strategies, prey preferences, and resting habits. Intriguingly, we found that several seals consistently returned to a deep-sea cabled video observatory, likely because they’ve learned to associate the sonar noise from the research instrument with the presence of food—a phenomenon known as the 'dinner bell' effect. *Abstract* The Ocean Networks Canada (ONC) cabled video-observatory at the Barkley Canyon Node (British Columbia, Canada) was recently the site of a Fish Acoustics and Attraction Experiment (FAAE), from May 21, 2022 to July 16, 2023, combining observations from High-Definition (HD) video, acoustic imaging sonar, and underwater sounds at a depth of 645 m, to examine the effects of light and bait on deep-sea fish and invertebrate behaviors. The unexpected presence of at least eight (six recurrent and two temporary) sub-adult male northern elephant seals (*Mirounga angustirostris*) was reported in 113 and 210 recordings out of 9737 HD and 2805 sonar videos at the site, respectively. Elephant seals were found at the site during seven distinct periods between June 22, 2022 and May 19, 2023. Ethograms provided insights into the seal’s deep-sea resting and foraging strategies, including prey selection. We hypothesized that the ability of elephant seals to perform repeated visits to the same site over long periods (> 10 days) was due to the noise generated by the sonar, suggesting that they learned to use that anthropogenic source as an indicator of food location, also known as the “dinner bell” effect. One interpretation is that elephant seals are attracted to the FAAE site due to the availability of prey and use the infrastructure as a foraging and resting site, but then take advantage of fish disturbance caused by the camera lights to improve foraging success. Our video observations demonstrated that northern elephant seals primarily focused on actively swimming sablefish (*Anoplopoma fimbria*), ignoring stationary or drifting prey. Moreover, we found that elephant seals appear to produce (voluntary or involuntary) infrasonic sounds in a foraging context. This study highlights the utility of designing marine observatories with spatially and temporally cross-referenced data collection from instruments representing multiple modalities of observation. The paper and videos can be found here: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0308461 Kind regards, Héloïse Frouin-Mouy ([email protected]) Assistant Scientist at the University of Miami (USA) Visiting Scientist at the University of Victoria (Canada)
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