University of IcelandAoki, KagariIsojunno, SaanaBellot, CharlotteIwata, TakashiKershaw, JoannaAkiyama, YuMartín López, Lucía M.Ramp, ChristianBiuw, MartinSwift, RenéWensveen, Paulus JacobusPomeroy, PatrickNarazaki, TomokoHall, AilsaSato, KatsufumiMiller, Patrick J.O.2025-11-202025-11-202021-01-27Aoki, 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, pp. 20202307. https://doi.org/10.1098/rspb.2020.23070962-84524197325854545f78-03ee-4a0e-8593-6da485980e7f8510047762733499785https://hdl.handle.net/20.500.11815/6473Publisher Copyright: © 2021 The Authors.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.193262120202307eninfo:eu-repo/semantics/openAccessanimal-borne sensorcetaceanfeeding seasonneutral buoyancytissue body densityUAVGeneral Immunology and MicrobiologyGeneral Biochemistry,Genetics and Molecular BiologyGeneral Environmental ScienceGeneral Agricultural and Biological Sciences/dk/atira/pure/researchoutput/researchoutputtypes/contributiontojournal/article10.1098/rspb.2020.2307