Dear all,
My colleagues and I are pleased to announce a new publication on the effects of
drag loading, e.g. from biologging tags, on marine mammals:
Swimming energy economy in bottlenose dolphins under variable drag loading.
van der Hoop, J.M., Fahlman, A., Shorter, K.A., Gabaldon, J., Rocho-Levine, J.,
Petrov, V., and Moore, M.J. 2018. Frontiers in Marine Science 5:465.
doi:10.3389/fmars.2018.00465.
The publication is available open access to all:
https://www.frontiersin.org/articles/10.3389/fmars.2018.00465/full
<https://www.frontiersin.org/articles/10.3389/fmars.2018.00465/full>
Abstract:
Instrumenting animals with tags contributes additional resistive forces
(weight, buoyancy, lift, and drag) that may result in increased energetic
costs; however, additional metabolic expense can be moderated by adjusting
behavior to maintain power output. We sought to increase hydrodynamic drag for
near-surface swimming bottlenose dolphins, to investigate the metabolic effect
of instrumentation. In this experiment, we investigate whether (1) metabolic
rate increases systematically with hydrodynamic drag loading from tags of
different sizes or (2) whether tagged individuals modulate speed, swimming
distance, and/or fluking motions under increased drag loading. We detected no
significant difference in oxygen consumption rates when four male dolphins
performed a repeated swimming task, but measured swimming speeds that were 34%
(>1 m s-1) slower in the highest drag condition. To further investigate this
observed response, we incrementally decreased and then increased drag in six
loading conditions. When drag was reduced, dolphins increased swimming speed
(+1.4 m s-1; +45%) and fluking frequency (+0.28 Hz; +16%). As drag was
increased, swimming speed (-0.96 m s-1; -23%) and fluking frequency (-0.14 Hz;
7%) decreased again. Results from computational fluid dynamics simulations
indicate that the experimentally observed changes in swimming speed would have
maintained the level of external drag forces experienced by the animals.
Together, these results indicate that dolphins may adjust swimming speed to
modulate the drag force opposing their motion during swimming, adapting their
behavior to maintain a level of energy economy during locomotion.
Summary Statement: Biologging and tracking tags add drag to study subjects.
When wearing tags of different sizes, dolphins changed their swimming paths,
speed, and movements to modulate power output and energy consumption.
All the best in 2019,
Julie
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Julie van der Hoop, PhD
Marie Skłodowska-Curie Research Fellow
Aarhus University, Aarhus DK
www.marinebioacoustics.com <http://www.marinebioacoustics.com/>
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