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Thibault M, Letourneur Y, Cleguer C, Bonneville C, Briand MJ, Derville S, Bustamante P, Garrigue C. C and N stable isotopes enlighten the trophic behaviour of the dugong (Dugong dugon). Sci Rep 2024; 14:896. [PMID: 38195771 PMCID: PMC10776846 DOI: 10.1038/s41598-023-50578-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Accepted: 12/21/2023] [Indexed: 01/11/2024] Open
Abstract
The dugong (Dugong dugon), a large marine mammal herbivore of the Indo-Pacific, is vulnerable to extinction at a global scale due to a combination of human-related threats including habitat degradation. The species forages on seagrass habitats (marine phanerogams) and plays a key role in the functioning and sensitivity of these declining coastal ecosystems. The trophic behaviour and plasticity of dugong populations in response to extrinsic and intrinsic factors are therefore crucial features to both dugong and seagrass conservation. Yet, this knowledge remains limited to few visual observations and analyses of mouth, stomach or faecal contents of stranded individuals. We take advantage of a long-term monitoring of stranded individuals from the endangered New Caledonian population to depict features of dugongs' trophic ecology from Carbon and Nitrogen stable isotopes. A total of 59 dugong skin samples were used to portrait the stable isotope niche of dugongs according to their sex and maturity. In light of previous work conducted in New Caledonia, a subset of these samples was used to model the trophic mix of dugong males and females. Our stable isotope mixing models used C and N isotope values of 10 taxa bbelonging to five divisions of metazoans, plants, and chromists. Our results represent the first estimate of the species dietary niche in the isotopic space. They suggest that the diet of dugong calves overlaps more with that of adult females (δ13C: - 6.38 ± 1.13 ‰; δ15N: 2.49 ± 1.10 ‰) than males (δ13C: - 5.92 ± 1.10 ‰; δ15N: 3.69 ± 1.28 ‰). Further, we highlight differences in the expected trophic mix of dugong adult males and females. From these, we formulate a sex-specific foraging behaviour hypothesis in dugongs, whereby lactating females could forage over smaller spatial ranges but more diverse food sources thanmales. The study emphasizes the importance of long-term stranding monitoring programs to study the ecology of marine mammals.. Finally, it depicts an ecological feature that may contribute to the sensitivity of vulnerable dugongs to ongoing changes on tropical coastal ecosystems.
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Affiliation(s)
- Martin Thibault
- Centre d'Écologie et des Sciences de la Conservation (CESCO), Muséum National d'Histoire Naturelle, Station de Biologie Marine, 1 Place de la Croix, 29900, Concarneau, France.
- UMR ENTROPIE (UR-IRD-IFREMER-CNRS-UNC), Labex-CORAIL, 98800, Nouméa, New Caledonia.
| | - Yves Letourneur
- UMR ENTROPIE (UR-IRD-IFREMER-CNRS-UNC), Labex-CORAIL, 98800, Nouméa, New Caledonia
| | - Christophe Cleguer
- Centre for Tropical Water and Aquatic Ecosystem Research (TropWATER), James Cook University, Townsville, Australia
| | - Claire Bonneville
- UMR ENTROPIE (UR-IRD-IFREMER-CNRS-UNC), Labex-CORAIL, 98800, Nouméa, New Caledonia
| | - Marine J Briand
- CRIOBE, USR 3278 EPHE-CNRS-UPVD, LabEx « Corail », PSL Research University, Université de Perpignan, Avenue Paul Alduy, 66860, Perpignan Cedex, France
| | - Solène Derville
- UMR ENTROPIE (UR-IRD-IFREMER-CNRS-UNC), Labex-CORAIL, 98800, Nouméa, New Caledonia
- Opération Cétacés, BP 12827, 98802, Nouméa, New Caledonia
| | - Paco Bustamante
- Littoral Environnement Et Sociétés (LIENSs), UMR 7266, CNRS-La Rochelle Université, 2 Rue Olympe de Gouges, 17000, La Rochelle, France
| | - Claire Garrigue
- UMR ENTROPIE (UR-IRD-IFREMER-CNRS-UNC), Labex-CORAIL, 98800, Nouméa, New Caledonia
- Opération Cétacés, BP 12827, 98802, Nouméa, New Caledonia
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Garrigue C, Bonneville CD, Cleguer C, Oremus M. Extremely low mtDNA diversity and high genetic differentiation reveal the precarious genetic status of dugongs in New Caledonia, South Pacific. J Hered 2022; 113:516-524. [PMID: 35665813 DOI: 10.1093/jhered/esac029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 06/01/2022] [Indexed: 11/13/2022] Open
Abstract
New Caledonia is home to one of the largest remaining populations of dugongs (Dugong dugon) and is located at the southeastern limit of the species' range. Local knowledge suggests that current levels of removal due to anthropogenic pressures are unsustainable, while trends suggest an ongoing decline in the population. Considering this unfavorable conservation context, this study aimed to assess the New Caledonian dugong population's resilience by determining its level of genetic diversity and degree of isolation relative to other populations. Mitochondrial DNA (mtDNA) control region sequences (n = 55) collected from live and dead dugongs in New Caledonia were compared to a global dataset of previously published sequences (n = 631) representing dugong populations throughout the species range. The New Caledonian dugong population displayed the lowest level of mtDNA diversity documented worldwide (3 haplotypes with 1 base pair difference), suggesting a recent origin of the current population through limited colonization events. Population structure analyses indicate a strong genetic differentiation with all the putative populations represented in the global dataset, including large neighbouring Australian populations. These results show that the dugong population in New Caledonia is particularly isolated, fragile, and vulnerable to anthropogenic threats and diseases with low potential for resilience through incoming gene flow. Our findings call for an instant conservation response and consideration for IUCN population assessment to support the long-term survival of the New Caledonian dugong population.
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Affiliation(s)
- Claire Garrigue
- UMR ENTROPIE (IRD, Université de La Réunion, Université de la Nouvelle-Calédonie, CNRS, IFREMER, Laboratoire d'Excellence - CORAIL, BPA5, Noumea, New Caledonia).,Opération Cétacés, BP12827, Nouméa, New Caledonia
| | - Claire Daisy Bonneville
- UMR ENTROPIE (IRD, Université de La Réunion, Université de la Nouvelle-Calédonie, CNRS, IFREMER, Laboratoire d'Excellence - CORAIL, BPA5, Noumea, New Caledonia).,Opération Cétacés, BP12827, Nouméa, New Caledonia
| | - Christophe Cleguer
- Centre for Tropical Water & Aquatic Ecosystem Research (TropWATER), James Cook University, Townsville, Australia
| | - Marc Oremus
- WWF-France Antenne Nouvelle-Calédonie, BP692, Nouméa, New Caledonia
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Ecoregional and temporal dynamics of dugong habitat use in a complex coral reef lagoon ecosystem. Sci Rep 2022; 12:552. [PMID: 35017573 PMCID: PMC8752826 DOI: 10.1038/s41598-021-04412-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 12/21/2021] [Indexed: 11/08/2022] Open
Abstract
Mobile marine species display complex and nonstationary habitat use patterns that require understanding to design effective management measures. In this study, the spatio-temporal habitat use dynamics of the vulnerable dugong (Dugong dugon) were modelled from 16 satellite-tagged individuals in the coral reef lagoonal ecosystems of New Caledonia, South Pacific. Dugong residence time was calculated along the interpolated tracks (9371 hourly positions) to estimate intensity of use in three contrasting ecoregions, previously identified through hierarchical clustering of lagoon topographic characteristics. Across ecoregions, differences were identified in dugong spatial intensity of use of shallow waters, deeper lagoon waters and the fore-reef shelf outside the barrier reef. Maps of dugong intensity of use were predicted from these ecological relationships and validated with spatial density estimates derived from aerial surveys conducted for population assessment. While high correlation was found between the two datasets, our study extended the spatial patterns of dugong distribution obtained from aerial surveys across the diel cycle, especially in shallow waters preferentially used by dugongs at night/dusk during high tide. This study has important implications for dugong conservation and illustrates the potential benefits of satellite tracking and dynamic habitat use modelling to inform spatial management of elusive and mobile marine mammals.
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