Body density of humpback whales (Megaptera novaengliae) in feeding aggregations estimated from hydrodynamic gliding performance

Narazaki, Tomoko ORCID: https://orcid.org/0000-0003-4513-3432 , Isojunno, Saana ORCID: https://orcid.org/0000-0002-2212-2135 , Nowacek, Douglas P., Swift, Rene, Friedlaender, Ari S., Ramp, Christian, Smout, Sophie, Aoki, Kagari, Deecke, Volker B. ORCID: https://orcid.org/0000-0003-2781-5915 , Sato, Katsufumi and Miller, Patrick J.O. (2018) Body density of humpback whales (Megaptera novaengliae) in feeding aggregations estimated from hydrodynamic gliding performance. PLoS ONE, 13 (7). e0200287.

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Abstract

Many baleen whales undertake annual fasting and feeding cycles, resulting in substantial changes in their body condition, an important factor affecting fitness. As a measure of lipid store body condition, tissue density of a few deep diving marine mammals has been estimated using a hydrodynamic glide model of drag and buoyancy forces. Here, we applied the method to shallow-diving humpback whales (Megaptera novaeangliae) in North Atlantic and Antarctic feeding aggregations. High-resolution 3-axis acceleration, depth and speed data were collected from 24 whales. Measured values of acceleration during 5 s glides were fitted to a hydrodynamic glide model to estimate unknown parameters (tissue density, drag term and diving gas volume) in a Bayesian framework. Estimated species-average tissue density (1031.6 ± 2.1 kg m-3, ±95% credible interval) indicates that humpback whale tissue is typically negatively buoyant although there was a large inter-individual variation ranging from 1025.2 to 1043.1 kg m-3. The precision of the individual estimates was substantially finer than the variation across different individual whales, demonstrating a progressive decrease in tissue density throughout the feeding season and comparably high lipid-store in pregnant females. The drag term (CDAm-1) was estimated to be relatively high, indicating a large effect of lift-related induced drag for humpback whales. Our results show that tissue density of shallow diving baleen whales can be estimated using the hydrodynamic gliding model, although cross-validation with other techniques is an essential next step. This method for estimating body condition is likely to be broadly applicable across a range of aquatic animals and environments.

Item Type:	Article
Journal / Publication Title:	PLoS ONE
Publisher:	Public Library of Science
ISSN:	1932-6203
Departments:	Academic Departments > Science, Natural Resources & Outdoor Studies (SNROS) > Forestry and Conservation
Depositing User:	Anna Lupton
Date Deposited:	11 Jul 2018 10:53
Last Modified:	12 Jan 2024 20:17
URI:	https://insight.cumbria.ac.uk/id/eprint/3980

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