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.

中文翻译：

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航空摄影测量和标签衍生的组织密度揭示了座头鲸在其觅食地的脂质储存身体状况模式

监测处于不同生活史阶段的自由放养海洋哺乳动物的身体状况对于了解它们的生态至关重要，因为它们必须积累足够的能量储备来生存和繁殖。然而，评估自由放养的海洋哺乳动物的身体状况具有挑战性。我们交叉验证了两种独立的方法来估计加拿大和挪威两个饲养场座头鲸 (Megaptera novaeangliae) 的身体状况：动物标签 (n = 59) 和航空摄影测量 (n = 55)。在头顶图像中具有较大长度标准化投影面积的鲸鱼（即鲸鱼看起来更胖）具有较低的估计组织体密度（TBD）（更大的脂质储存）。将贝叶斯分层模型中的两个测量值联系起来，以估计真正的潜在（隐藏）组织体密度 (uTBD)，我们发现与成年雄性和静止雌性相比，怀孕雌性的 uTBD 较低（-3.5 kg m-3），而在哺乳期雌性中则更高（+6.0 kg m-3）。在早期的觅食季节，挪威的鲸鱼比加拿大的负浮力更大（+5.0 kg m-3），这可能是由于从繁殖区迁徙的时间更长。虽然 uTBD 在整个生活史特征的摄食季节期间下降，但鲸鱼组织在摄食季节后期仍保持负浮力 (1035.3 ± 3.8 kg m-3)。这项研究增加了对这些独立方法的有效性的信心，以估计自由放养的鲸鱼的身体状况。0 kg m−3) 在早期摄食季节，挪威比加拿大多，这可能是由于从繁殖区迁徙的时间更长。虽然 uTBD 在整个生活史特征的摄食季节期间下降，但鲸鱼组织在摄食季节后期仍保持负浮力 (1035.3 ± 3.8 kg m-3)。这项研究增加了对这些独立方法的有效性的信心，以估计自由放养的鲸鱼的身体状况。0 kg m−3) 在早期摄食季节，挪威比加拿大多，这可能是由于从繁殖区迁徙的时间更长。虽然 uTBD 在整个生活史特征的摄食季节期间下降，但鲸鱼组织在摄食季节后期仍保持负浮力 (1035.3 ± 3.8 kg m-3)。这项研究增加了对这些独立方法的有效性的信心，以估计自由放养的鲸鱼的身体状况。