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Aerial photogrammetry and tag-derived tissue density reveal patterns of lipid-store body condition of humpback whales on their feeding grounds

Aerial photogrammetry and tag-derived tissue density reveal patterns of lipid-store body condition of humpback whales on their feeding grounds


Title: Aerial photogrammetry and tag-derived tissue density reveal patterns of lipid-store body condition of humpback whales on their feeding grounds
Author: Aoki, Kagari
Isojunno, Saana
Bellot, Charlotte
Iwata, Takashi
Kershaw, Joanna
Akiyama, Yu
Martín López, Lucía M.
Ramp, Christian
Biuw, Martin
Swift, René
... 6 more authors Show all authors
Date: 2021-01-27
Language: English
Scope:
University/Institute: University of Iceland
Series: Proceedings of the Royal Society B: Biological Sciences; 288(1943)
ISSN: 0962-8452
DOI: https://doi.org/10.1098/rspb.2020.2307
Subject: Hnúfubakur; Sjávarlíffræði; animal-borne sensor; cetacean; feeding season; neutral buoyancy; tissue body density; UAV; Immunology and Microbiology (all); Biochemistry, Genetics and Molecular Biology (all); Environmental Science (all); Agricultural and Biological Sciences (all)
URI: https://hdl.handle.net/20.500.11815/2715

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Citation:

Aoki , K , Isojunno , S , Bellot , C , Iwata , T , Kershaw , J , Akiyama , Y , Martín López , L M , Ramp , C , Biuw , M , Swift , R , Wensveen , P J , Pomeroy , P , Narazaki , T , Hall , A , Sato , K & Miller , P J O 2021 , ' Aerial photogrammetry and tag-derived tissue density reveal patterns of lipid-store body condition of humpback whales on their feeding grounds ' , Proceedings of the Royal Society B: Biological Sciences , vol. 288 , no. 1943 , 20202307 . https://doi.org/10.1098/rspb.2020.2307

Abstract:

Monitoring the body condition of free-ranging marine mammals at different life-history stages is essential to understand their ecology as they must accumulate sufficient energy reserves for survival and reproduction. However, assessing body condition in free-ranging marine mammals is challenging. We cross-validated two independent approaches to estimate the body condition of humpback whales (Megaptera novaeangliae) at two feeding grounds in Canada and Norway: animal-borne tags (n = 59) and aerial photogrammetry (n = 55). Whales that had a large length-standardized projected area in overhead images (i.e. whales looked fatter) had lower estimated tissue body density (TBD) (greater lipid stores) from tag data. Linking both measurements in a Bayesian hierarchical model to estimate the true underlying (hidden) tissue body density (uTBD), we found uTBD was lower (-3.5 kg m -3) in pregnant females compared to adult males and resting females, while in lactating females it was higher (+6.0 kg m -3). Whales were more negatively buoyant (+5.0 kg m -3) in Norway than Canada during the early feeding season, possibly owing to a longer migration from breeding areas. While uTBD decreased over the feeding season across life-history traits, whale tissues remained negatively buoyant (1035.3 ± 3.8 kg m -3) in the late feeding season. This study adds confidence to the effectiveness of these independent methods to estimate the body condition of free-ranging whales.

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Publisher Copyright: © 2021 The Authors.

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