Jouventin P. & Aubin T. (2000). Acoustic convergence between two nocturnal burrowing seabirds : Experiments with a penguin Eudyptula minor and a shearwater Puffinus tenuirostris. Ibis (Lond. 1859), 142(4), 645–656.
Abstract: The evolution of acoustic signals is influenced by environmental constraints. We studied two sympatric but unrelated seabirds: the Little Penguin Eudyptula minor and Short-tailed Shearwater Puffinus tenuirostris, to examine the degree to which similarities in their ecology had led to convergence in their calls. Both species nest in burrows in Southern Australia and, at night, are highly vocal and territorial. First, we analysed the physical characteristics of the territorial call. Secondly, we studied the transmission of calls through burrows and varying distances through vegetation. Thirdly, we used playback experiments of natural signals to demonstrate that the response disappears between 4-8 m, and of modified signals to understand the coding-decoding process linked to the territorial function of the call. The structure of the territorial calls of the two species clearly differs, but both species produce a succession of gaps in amplitude and frequency, and a high degree of redundancy. Our experiments show that, to decode the territorial message, birds pay attention only to parameters that are less degraded during propagation and ignore fine details of structure that are quickly degraded, even at relatively short distances (< 8 m). In both species, territorial information is mainly conveyed by the rhythmic succession of two sounds (syllables or subsyllables), birds paying attention to the FM structure of these successive sounds but not to the AM. This convergent coding is adaptive in that it reduces the possibility that the meaning may be distorted by interference from noise and acoustic screening.
Keywords: Nocturnal animal ; Sympatry ; Song ; Acoustic communication ; Syntax ; Frequency spectrum ; Sound propagation ; Burrow ; Territorial behavior ; Interspecific comparison ; South Australia ; Philip Island ; Australia ; Oceania ; Marine environment ; Sound production ; Aves ; Vertebrata
Programme: 109;354
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Nolwenn Béhagle, Cédric Cotté, Anne Lebourges-Dhaussy, Gildas Roudaut, Guy Duhamel, Patrice Brehmer, Erwan Josse, Yves Cherel. (2017). Acoustic distribution of discriminated micronektonic organisms from a bi-frequency processing: The case study of eastern Kerguelen oceanic waters (Vol. 156).
Abstract: Despite its ecological importance, micronekton remains one of the least investigated components of the open-ocean ecosystems. Our main goal was to characterize micronektonic organisms using bi-frequency acoustic data (38 and 120kHz) by calibrating an algorithm tool that discriminates groups of scatterers in the top 300m of the productive oceanic zone east of Kerguelen Islands (Indian sector of the Southern Ocean). The bi-frequency algorithm was calibrated from acoustic properties of mono-specific biological samples collected with trawls, thus allowing to discriminate three acoustic groups of micronekton: (i) “gas-bearing” (ΔSv,120-38<−1dB), (ii) “fluid-like” (ΔSv,120-38>2dB), and (iii) “undetermined” scatterers (−1<ΔSv,120-38<2dB). The three groups likely correspond biologically to gas-filled swimbladder fish (myctophids), crustaceans (euphausiids and hyperiid amphipods), and other marine organisms potentially present in these waters and containing either lipid-filled or no inclusion (e.g. other myctophids), respectively. The Nautical Area Scattering Coefficient (NASC) was used (echo-integration cells of 10m long and 1m deep) between 30 and 300m depth as a proxy of relative biomass of acoustic targets. The distribution of NASC values showed a complex pattern according to: (i) the three acoustically-defined groups, (ii) the type of structures (patch vs. layers) and (iii) the timing of the day (day/night cycle). NASC values were higher at night than during the day. A large proportion of scatterers occurred in layers while patches, that mainly encompass gas-bearing organisms, are especially observed during daytime. This method provided an essential descriptive baseline of the spatial distribution of micronekton and a relevant approach to (i) link micronektonic group to physical parameters to define their habitats, (ii) investigate trophic interactions by combining active acoustic and top predator satellite tracking, and (iii) study the functioning of the pelagic ecosystems at various spatio-temporal scales.
Keywords: Acoustics Euphausiid Kerguelen Myctophid Southern Ocean
Programme: 109
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Nolwenn Béhagle, Cédric Cotté, Anne Lebourges-Dhaussy, Gildas Roudaut, Guy Duhamel, Patrice Brehmer, Erwan Josse, Yves Cherel. (2017). Acoustic distribution of discriminated micronektonic organisms from a bi-frequency processing: The case study of eastern Kerguelen oceanic waters (Vol. 156).
Abstract: Despite its ecological importance, micronekton remains one of the least investigated components of the open-ocean ecosystems. Our main goal was to characterize micronektonic organisms using bi-frequency acoustic data (38 and 120kHz) by calibrating an algorithm tool that discriminates groups of scatterers in the top 300m of the productive oceanic zone east of Kerguelen Islands (Indian sector of the Southern Ocean). The bi-frequency algorithm was calibrated from acoustic properties of mono-specific biological samples collected with trawls, thus allowing to discriminate three acoustic groups of micronekton: (i) “gas-bearing” (ΔSv,120-38<−1dB), (ii) “fluid-like” (ΔSv,120-38>2dB), and (iii) “undetermined” scatterers (−1<ΔSv,120-38<2dB). The three groups likely correspond biologically to gas-filled swimbladder fish (myctophids), crustaceans (euphausiids and hyperiid amphipods), and other marine organisms potentially present in these waters and containing either lipid-filled or no inclusion (e.g. other myctophids), respectively. The Nautical Area Scattering Coefficient (NASC) was used (echo-integration cells of 10m long and 1m deep) between 30 and 300m depth as a proxy of relative biomass of acoustic targets. The distribution of NASC values showed a complex pattern according to: (i) the three acoustically-defined groups, (ii) the type of structures (patch vs. layers) and (iii) the timing of the day (day/night cycle). NASC values were higher at night than during the day. A large proportion of scatterers occurred in layers while patches, that mainly encompass gas-bearing organisms, are especially observed during daytime. This method provided an essential descriptive baseline of the spatial distribution of micronekton and a relevant approach to (i) link micronektonic group to physical parameters to define their habitats, (ii) investigate trophic interactions by combining active acoustic and top predator satellite tracking, and (iii) study the functioning of the pelagic ecosystems at various spatio-temporal scales.
Keywords: Acoustics Euphausiid Kerguelen Myctophid Southern Ocean
Programme: 109
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Whittington J.D., Le Maho Y., Boureau M., Morinay J., Amelineau F., Le Bohec C. (2014). Acoustic features of display calls may reveal breeding status and individual quality in emperor penguins.
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J.D. Whittington, Y. Le Maho, M. Boureau, J. Morinay, F. Amelineau, C. Le Bohec. (2014). Acoustic features of display calls may reveal breeding status and individual quality in emperor penguins..
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Louise Day, Joffrey Jouma'a, Julien Bonnel, Christophe Guinet. (2017). Acoustic measurements of post-dive cardiac responses in southern elephant seals (Mirounga leonina) during surfacing at sea (Vol. 220).
Abstract: Skip to Next Section Measuring physiological data in free-ranging marine mammals remains challenging, owing to their far-ranging foraging habitat. Yet, it is important to understand how these divers recover from effort expended underwater, as marine mammals can perform deep and recurrent dives. Among them, southern elephant seals (Mirounga leonina) are one of the most extreme divers, diving continuously at great depth and for long duration while travelling over large distances within the Southern Ocean. To determine how they manage post-dive recovery, we deployed hydrophones on four post-breeding female southern elephant seals. Cardiac data were extracted from sound recordings when the animal was at the surface, breathing. Mean heart rate at the surface was 102.4±4.9 beats min−1 and seals spent on average 121±20 s breathing. During these surface intervals, the instantaneous heart rate increased with time. Elephant seals are assumed to drastically slow their heart rate (bradycardia) while they are deep underwater, and increase it (tachycardia) during the ascent towards the surface. Our finding suggests that tachycardia continues while the animal stays breathing at the surface. Also, the measured mean heart rate at the surface was unrelated to the duration and swimming effort of the dive prior to the surface interval. Recovery (at the surface) after physical effort (underwater) appears to be related to the overall number of heart beats performed at the surface, and therefore total surface duration. Southern elephant seals recover from dives by adjusting the time spent at the surface rather than their heart rate.
Programme: 109
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Louise Day, Joffrey Jouma'a, Julien Bonnel, Christophe Guinet. (2017). Acoustic measurements of post-dive cardiac responses in southern elephant seals (Mirounga leonina) during surfacing at sea (Vol. 220).
Abstract: Skip to Next Section Measuring physiological data in free-ranging marine mammals remains challenging, owing to their far-ranging foraging habitat. Yet, it is important to understand how these divers recover from effort expended underwater, as marine mammals can perform deep and recurrent dives. Among them, southern elephant seals (Mirounga leonina) are one of the most extreme divers, diving continuously at great depth and for long duration while travelling over large distances within the Southern Ocean. To determine how they manage post-dive recovery, we deployed hydrophones on four post-breeding female southern elephant seals. Cardiac data were extracted from sound recordings when the animal was at the surface, breathing. Mean heart rate at the surface was 102.4±4.9 beats min−1 and seals spent on average 121±20 s breathing. During these surface intervals, the instantaneous heart rate increased with time. Elephant seals are assumed to drastically slow their heart rate (bradycardia) while they are deep underwater, and increase it (tachycardia) during the ascent towards the surface. Our finding suggests that tachycardia continues while the animal stays breathing at the surface. Also, the measured mean heart rate at the surface was unrelated to the duration and swimming effort of the dive prior to the surface interval. Recovery (at the surface) after physical effort (underwater) appears to be related to the overall number of heart beats performed at the surface, and therefore total surface duration. Southern elephant seals recover from dives by adjusting the time spent at the surface rather than their heart rate.
Programme: 109
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Béhagle Nolwenn, Cotté Cédric, Ryan Tim E., Gauthier Olivier, Roudaut Gildas, Brehmer Patrice, Josse Erwan, Cherel Yves. (2016). Acoustic micronektonic distribution is structured by macroscale oceanographic processes across 20–50°S latitudes in the South-Western Indian Ocean. Deep Sea Res. Part II Top. Stud. Oceanogr., 110, 20–32.
Abstract: Micronekton constitutes the largest unexploited marine biomass worldwide. It is one of the most conspicuous and ecologically important components of the still poorly known mesopelagic ecosystem. Acoustic data were collected from both fishing and research vessels along 18 transects for a total of 47 682 linear kilometers to investigate large-scale distribution of micronekton over a long latitudinal gradient (20–50°S) and two contrasted seasons (summer and winter) in the South-Western Indian Ocean. Acoustic backscatter at 38 kHz was used as a proxy of mid-water organisms' abundance (0–800 m depth). Two consistent features were diel vertical migration of backscatters and vertical distribution of micronekton in three distinct layers, namely the surface (SL), intermediate (IL) and deep (DL) layers. Satellite remote sensing data was used to position oceanic fronts, and hence define water masses, from the tropical to low Antarctic zones. A key finding of this study was the significant correlation observed between abundance and distribution of acoustic backscatter and position relative to these front and water masses. Total backscatter peaked in the subtropical zone, with low abundances in the colder Polar Frontal Zone. The high overall abundances in subtropical waters resulted mainly from high backscatters in the IL and DL that contrasted with low SL values, especially during the day (2–11%). The warmer the waters, the higher SL backscatter was, with the highest absolute and relative (38–51% of the total abundance) values observed at night in the Tropical Zone and the lowest abundance in the Antarctic Zone. No significant seasonal pattern was found, but SL backscatters were very low in winter compared to summer in the Polar Frontal Zone. Moreover, the Northern winter shift of the fronts induced a Northern latitudinal shift of the peak in abundance from summer to winter. The present study highlights the value of building large acoustic databases collected from both research and fishing vessels. The method provides unique opportunities to gather basic information on micronekton and is an essential step to describe oceanic zones of relevant biological interest in terms of trophic ecology.
Programme: 109
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Mathevon N., Charrier I. & Jouventin P. (2003). Acoustic Potential of Individuality Coding : A comparative study between two closely related gulls nesting differently Larus dominicanus and genei. C.R. Acad. Sci. Paris, 326, 329–337.
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Searby A., Jouventin P. & Aubin T. (2004). Acoustic recognition in macaroni penguins: a novel signature system. Animal behaviour, 67, 615–625.
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