An evaluation of three-dimensional photogrammetric and morphometric techniques for estimating volume and mass in Weddell seals Leptonychotes weddellii.
Body mass dynamics of animals can indicate critical associations between extrinsic factors and population vital rates. Photogrammetry can be used to estimate mass of individuals in species whose life histories make it logistically difficult to obtain direct body mass measurements. Such studies typic...
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ftdoajarticles:oai:doaj.org/article:6e78b2ecfc674914a227987fac856e55 2023-05-15T18:43:24+02:00 An evaluation of three-dimensional photogrammetric and morphometric techniques for estimating volume and mass in Weddell seals Leptonychotes weddellii. Roxanne S Beltran Brandi Ruscher-Hill Amy L Kirkham Jennifer M Burns 2018-01-01T00:00:00Z https://doi.org/10.1371/journal.pone.0189865 https://doaj.org/article/6e78b2ecfc674914a227987fac856e55 EN eng Public Library of Science (PLoS) http://europepmc.org/articles/PMC5761831?pdf=render https://doaj.org/toc/1932-6203 1932-6203 doi:10.1371/journal.pone.0189865 https://doaj.org/article/6e78b2ecfc674914a227987fac856e55 PLoS ONE, Vol 13, Iss 1, p e0189865 (2018) Medicine R Science Q article 2018 ftdoajarticles https://doi.org/10.1371/journal.pone.0189865 2022-12-31T12:37:44Z Body mass dynamics of animals can indicate critical associations between extrinsic factors and population vital rates. Photogrammetry can be used to estimate mass of individuals in species whose life histories make it logistically difficult to obtain direct body mass measurements. Such studies typically use equations to relate volume estimates from photogrammetry to mass; however, most fail to identify the sources of error between the estimated and actual mass. Our objective was to identify the sources of error that prevent photogrammetric mass estimation from directly predicting actual mass, and develop a methodology to correct this issue. To do this, we obtained mass, body measurements, and scaled photos for 56 sedated Weddell seals (Leptonychotes weddellii). After creating a three-dimensional silhouette in the image processing program PhotoModeler Pro, we used horizontal scale bars to define the ground plane, then removed the below-ground portion of the animal's estimated silhouette. We then re-calculated body volume and applied an expected density to estimate animal mass. We compared the body mass estimates derived from this silhouette slice method with estimates derived from two other published methodologies: body mass calculated using photogrammetry coupled with a species-specific correction factor, and estimates using elliptical cones and measured tissue densities. The estimated mass values (mean ± standard deviation 345±71 kg for correction equation, 346±75 kg for silhouette slice, 343±76 kg for cones) were not statistically distinguishable from each other or from actual mass (346±73 kg) (ANOVA with Tukey HSD post-hoc, p>0.05 for all pairwise comparisons). We conclude that volume overestimates from photogrammetry are likely due to the inability of photo modeling software to properly render the ventral surface of the animal where it contacts the ground. Due to logistical differences between the "correction equation", "silhouette slicing", and "cones" approaches, researchers may find one technique more ... Article in Journal/Newspaper Weddell Seals Directory of Open Access Journals: DOAJ Articles Weddell PLOS ONE 13 1 e0189865 |
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language |
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topic |
Medicine R Science Q |
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Medicine R Science Q Roxanne S Beltran Brandi Ruscher-Hill Amy L Kirkham Jennifer M Burns An evaluation of three-dimensional photogrammetric and morphometric techniques for estimating volume and mass in Weddell seals Leptonychotes weddellii. |
topic_facet |
Medicine R Science Q |
description |
Body mass dynamics of animals can indicate critical associations between extrinsic factors and population vital rates. Photogrammetry can be used to estimate mass of individuals in species whose life histories make it logistically difficult to obtain direct body mass measurements. Such studies typically use equations to relate volume estimates from photogrammetry to mass; however, most fail to identify the sources of error between the estimated and actual mass. Our objective was to identify the sources of error that prevent photogrammetric mass estimation from directly predicting actual mass, and develop a methodology to correct this issue. To do this, we obtained mass, body measurements, and scaled photos for 56 sedated Weddell seals (Leptonychotes weddellii). After creating a three-dimensional silhouette in the image processing program PhotoModeler Pro, we used horizontal scale bars to define the ground plane, then removed the below-ground portion of the animal's estimated silhouette. We then re-calculated body volume and applied an expected density to estimate animal mass. We compared the body mass estimates derived from this silhouette slice method with estimates derived from two other published methodologies: body mass calculated using photogrammetry coupled with a species-specific correction factor, and estimates using elliptical cones and measured tissue densities. The estimated mass values (mean ± standard deviation 345±71 kg for correction equation, 346±75 kg for silhouette slice, 343±76 kg for cones) were not statistically distinguishable from each other or from actual mass (346±73 kg) (ANOVA with Tukey HSD post-hoc, p>0.05 for all pairwise comparisons). We conclude that volume overestimates from photogrammetry are likely due to the inability of photo modeling software to properly render the ventral surface of the animal where it contacts the ground. Due to logistical differences between the "correction equation", "silhouette slicing", and "cones" approaches, researchers may find one technique more ... |
format |
Article in Journal/Newspaper |
author |
Roxanne S Beltran Brandi Ruscher-Hill Amy L Kirkham Jennifer M Burns |
author_facet |
Roxanne S Beltran Brandi Ruscher-Hill Amy L Kirkham Jennifer M Burns |
author_sort |
Roxanne S Beltran |
title |
An evaluation of three-dimensional photogrammetric and morphometric techniques for estimating volume and mass in Weddell seals Leptonychotes weddellii. |
title_short |
An evaluation of three-dimensional photogrammetric and morphometric techniques for estimating volume and mass in Weddell seals Leptonychotes weddellii. |
title_full |
An evaluation of three-dimensional photogrammetric and morphometric techniques for estimating volume and mass in Weddell seals Leptonychotes weddellii. |
title_fullStr |
An evaluation of three-dimensional photogrammetric and morphometric techniques for estimating volume and mass in Weddell seals Leptonychotes weddellii. |
title_full_unstemmed |
An evaluation of three-dimensional photogrammetric and morphometric techniques for estimating volume and mass in Weddell seals Leptonychotes weddellii. |
title_sort |
evaluation of three-dimensional photogrammetric and morphometric techniques for estimating volume and mass in weddell seals leptonychotes weddellii. |
publisher |
Public Library of Science (PLoS) |
publishDate |
2018 |
url |
https://doi.org/10.1371/journal.pone.0189865 https://doaj.org/article/6e78b2ecfc674914a227987fac856e55 |
geographic |
Weddell |
geographic_facet |
Weddell |
genre |
Weddell Seals |
genre_facet |
Weddell Seals |
op_source |
PLoS ONE, Vol 13, Iss 1, p e0189865 (2018) |
op_relation |
http://europepmc.org/articles/PMC5761831?pdf=render https://doaj.org/toc/1932-6203 1932-6203 doi:10.1371/journal.pone.0189865 https://doaj.org/article/6e78b2ecfc674914a227987fac856e55 |
op_doi |
https://doi.org/10.1371/journal.pone.0189865 |
container_title |
PLOS ONE |
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13 |
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1 |
container_start_page |
e0189865 |
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1766233793915518976 |