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. 2023 Mar 14;13(6):1048.
doi: 10.3390/ani13061048.

First Description of the Underwater Sounds in the Mediterranean Monk Seal Monachus monachus in Greece: Towards Establishing a Vocal Repertoire

Isabelle Charrier  1 , Chloé Huetz  1 , Léa Prevost  1 , Panagiotis Dendrinos  2 , Alexandros A Karamanlidis  2
Affiliations

First Description of the Underwater Sounds in the Mediterranean Monk Seal Monachus monachus in Greece: Towards Establishing a Vocal Repertoire

Isabelle Charrier et al. Animals (Basel). .

Abstract

The Mediterranean monk seal Monachus monachus is one of the most endangered pinnipeds in the world, and is classified as "Endangered" by the International Union for the Conservation of Nature. Any additional knowledge about the species is invaluable to its effective conservation. In the present study, we deployed an autonomous underwater recorder in an important reproductive area of the Mediterranean monk seal in Greece to describe its underwater vocal repertoire. Over the 330 h of continuous recordings, 9231 vocalizations were labelled as potentially produced by Mediterranean monk seals, and 1694 good quality calls were analyzed. We defined 18 call types divided into three main call categories: harmonic, noisy, and pulsative calls. We also described the soundscape in which this endangered species lives and found that human activities around the two main pupping caves had a strong impact on the sonic environment of these seals: the noise level produced by boat traffic was high, and occurred on an hourly (25 to 50 min/hour) and daily basis (10.8 to 16.9 h/day). Such high levels of noise might not only impair the communication of the species, but also impact its survival, as chronic noise can induce physiological stress.

Keywords: Mediterranean monk seal; Pinnipedia; acoustic monitoring; anthropogenic noise; conservation; underwater vocalization.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Spectrograms of the 12 harmonic call types. Bark (a), croak (b), cry (c), gloo (d), gloogloo (e), groan (f), moan (g), scream (h), whine (i), whoo (j), wop (k), wom (l).
Figure 2
Figure 2
Spectrograms of the three noisy call types. Growl (a), hiccup (b), squeak (c).
Figure 3
Figure 3
Spectrograms of the three pulsative call types. Clap (a), knock (b), rumble (c).
Figure 4
Figure 4
Example of a long-term spectrogram average of a 24-hours day of continuous recording (19 November 2021). The background “noise” generated by snapping shrimps (i.e., 1500–5000 Hz, red rectangle) and the “noise” generated by boat traffic (blue rectangle) present in the study area are presented. Monk seal underwater vocalizations can not be identified on the LTSA, as they are very short and masked by the vessel noise.
Figure 5
Figure 5
Power Spectrum Density (PSD, (a)), Broadband (BB, (b)), and Octave band level (OL, (c)) plots. Plots were computed over the 13 days of continuous recordings (19 November–1 December 2021). For the PSD plot, the median values are presented in black and the 10, 25, 75, and 90 percentiles in red, blue, cyan, and green, respectively. For the BB plot, the median is presented in black, and the white and blue background patterns indicate the 24-hours periods (i.e., a full day of recording). For the OL plot, we selected three representative frequency bands: the 125 Hz-band (grey) that represented boat “noise”, the 500 Hz-band (black) in which monk seal vocalizations were recorded, and the 2000 Hz-band (green) in which the snapping shrimps dominated.
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References

    1. Karamanlidis A., Dendrinos P. Monachus monachus, The IUCN Red List Threat Species. 2015. [(accessed on 22 December 2022)]. Available online: https://www.iucnredlist.org/species/13653/117647375#errata.
    1. Karamanlidis A.A. MOm/Hellenic Society for the Study and Protection of the Monk Seal, Athens, Greece. 2023. Unpublished work .
    1. Adamantopoulou S., Karamanlidis A.A., Dendrinos P., Gimenez O. Citizen Science Indicates Significant Range Recovery and Defines New Conservation Priorities for Earth’s Most Endangered Pinniped in Greece. Anim. Conserv. 2022;26:115–125. doi: 10.1111/acv.12806. - DOI
    1. Nicolaou H., Dendrinos P., Marcou M., Michaelides S., Karamanlidis A.A. Re-Establishment of the Mediterranean Monk Seal Monachus monachus in Cyprus: Priorities for Conservation. ORYX. 2021;55:526–528. doi: 10.1017/S0030605319000759. - DOI
    1. Dendrinos D., Karamanlidis A.A., Adamantopoulou S., Koemtzopoulos K., Komninou A., Tounta E. NoLIFE-IP 4 NATURA: Integrated Actions for the Conservation and Management of Natura 2000 Sites, Species, Habitats and Ecosystems in Greece: Deliverable Action A.1: Action Plan for the Mediterranean Monk Seal (Monachus monachus) Hellenic Ministry of Environment and Energy; Athens, Greece: 2020. pp. 1–105. Report.

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