The utility of accelerometers to predict stroke rate in captive fur seals and sea lions

The energy expenditure of free-living fur seals and sea lions is difficult to measure directly, but may be indirectly derived from flipper stroke rate. We filmed 10 captive otariids swimming with accelerometers either attached to a harness (Daily Diary: sampling frequency 32 Hz, N=4) or taped to the...

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Autores principales: Ladds, Monique A., Rosen, David A., Slip, David J., Harcourt, Robert G.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Company of Biologists Ltd 2017
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5612241/
https://www.ncbi.nlm.nih.gov/pubmed/28798149
http://dx.doi.org/10.1242/bio.027029
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author Ladds, Monique A.
Rosen, David A.
Slip, David J.
Harcourt, Robert G.
author_facet Ladds, Monique A.
Rosen, David A.
Slip, David J.
Harcourt, Robert G.
author_sort Ladds, Monique A.
collection PubMed
description The energy expenditure of free-living fur seals and sea lions is difficult to measure directly, but may be indirectly derived from flipper stroke rate. We filmed 10 captive otariids swimming with accelerometers either attached to a harness (Daily Diary: sampling frequency 32 Hz, N=4) or taped to the fur (G6a+: 25 Hz, N=6). We used down sampling to derive four recording rates from each accelerometer (Daily Diary: 32, 16, 8, 4 Hz; G6a+: 25, 20, 10, 5 Hz). For each of these sampling frequencies, we derived 20 combinations of two parameters (RMW, the window size used to calculate the running mean; and m, the minimum number of points smaller than a local maxima used to detect a peak) from the dynamic acceleration of x, z and x+z, to estimate stroke rate from the accelerometers. These estimates differed by up to ∼20% in comparison to the actual number of foreflipper strokes counted from videos. RMW and the choice of axis used to make the calculations (x, z or x+z) had little effect on the overall differences, though the variability was reduced when using x+z. The best m varied depending on the axis used and the sampling frequency; a larger m was needed for higher sampling frequencies. This study demonstrates that when parameters are appropriately tuned, accelerometers are a simple yet valid tool for estimating the stroke rates of swimming otariids.
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spelling pubmed-56122412017-09-29 The utility of accelerometers to predict stroke rate in captive fur seals and sea lions Ladds, Monique A. Rosen, David A. Slip, David J. Harcourt, Robert G. Biol Open Methods & Techniques The energy expenditure of free-living fur seals and sea lions is difficult to measure directly, but may be indirectly derived from flipper stroke rate. We filmed 10 captive otariids swimming with accelerometers either attached to a harness (Daily Diary: sampling frequency 32 Hz, N=4) or taped to the fur (G6a+: 25 Hz, N=6). We used down sampling to derive four recording rates from each accelerometer (Daily Diary: 32, 16, 8, 4 Hz; G6a+: 25, 20, 10, 5 Hz). For each of these sampling frequencies, we derived 20 combinations of two parameters (RMW, the window size used to calculate the running mean; and m, the minimum number of points smaller than a local maxima used to detect a peak) from the dynamic acceleration of x, z and x+z, to estimate stroke rate from the accelerometers. These estimates differed by up to ∼20% in comparison to the actual number of foreflipper strokes counted from videos. RMW and the choice of axis used to make the calculations (x, z or x+z) had little effect on the overall differences, though the variability was reduced when using x+z. The best m varied depending on the axis used and the sampling frequency; a larger m was needed for higher sampling frequencies. This study demonstrates that when parameters are appropriately tuned, accelerometers are a simple yet valid tool for estimating the stroke rates of swimming otariids. The Company of Biologists Ltd 2017-08-10 /pmc/articles/PMC5612241/ /pubmed/28798149 http://dx.doi.org/10.1242/bio.027029 Text en © 2017. Published by The Company of Biologists Ltd http://creativecommons.org/licenses/by/3.0This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.
spellingShingle Methods & Techniques
Ladds, Monique A.
Rosen, David A.
Slip, David J.
Harcourt, Robert G.
The utility of accelerometers to predict stroke rate in captive fur seals and sea lions
title The utility of accelerometers to predict stroke rate in captive fur seals and sea lions
title_full The utility of accelerometers to predict stroke rate in captive fur seals and sea lions
title_fullStr The utility of accelerometers to predict stroke rate in captive fur seals and sea lions
title_full_unstemmed The utility of accelerometers to predict stroke rate in captive fur seals and sea lions
title_short The utility of accelerometers to predict stroke rate in captive fur seals and sea lions
title_sort utility of accelerometers to predict stroke rate in captive fur seals and sea lions
topic Methods & Techniques
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5612241/
https://www.ncbi.nlm.nih.gov/pubmed/28798149
http://dx.doi.org/10.1242/bio.027029
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