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...
Main Authors: | , , , |
---|---|
Other Authors: | |
Format: | Article in Journal/Newspaper |
Language: | unknown |
Published: |
eScholarship, University of California
2018
|
Subjects: | |
Online Access: | https://escholarship.org/uc/item/11g8z7g9 |
id |
ftcdlib:oai:escholarship.org:ark:/13030/qt11g8z7g9 |
---|---|
record_format |
openpolar |
spelling |
ftcdlib:oai:escholarship.org:ark:/13030/qt11g8z7g9 2023-11-05T03:45:25+01:00 An evaluation of three-dimensional photogrammetric and morphometric techniques for estimating volume and mass in Weddell seals Leptonychotes weddellii Beltran, Roxanne S Ruscher-Hill, Brandi Kirkham, Amy L Burns, Jennifer M Ropert-Coudert, Yan e0189865 2018-01-01 application/pdf https://escholarship.org/uc/item/11g8z7g9 unknown eScholarship, University of California qt11g8z7g9 https://escholarship.org/uc/item/11g8z7g9 public PLOS ONE, vol 13, iss 1 Earth Sciences Archaeology History Heritage and Archaeology Animals Biometry Body Size Body Weight Female Imaging Three-Dimensional Photogrammetry Seals Earless Specific Gravity General Science & Technology article 2018 ftcdlib 2023-10-09T18:05:21Z 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 University of California: eScholarship |
institution |
Open Polar |
collection |
University of California: eScholarship |
op_collection_id |
ftcdlib |
language |
unknown |
topic |
Earth Sciences Archaeology History Heritage and Archaeology Animals Biometry Body Size Body Weight Female Imaging Three-Dimensional Photogrammetry Seals Earless Specific Gravity General Science & Technology |
spellingShingle |
Earth Sciences Archaeology History Heritage and Archaeology Animals Biometry Body Size Body Weight Female Imaging Three-Dimensional Photogrammetry Seals Earless Specific Gravity General Science & Technology Beltran, Roxanne S Ruscher-Hill, Brandi Kirkham, Amy L Burns, Jennifer M An evaluation of three-dimensional photogrammetric and morphometric techniques for estimating volume and mass in Weddell seals Leptonychotes weddellii |
topic_facet |
Earth Sciences Archaeology History Heritage and Archaeology Animals Biometry Body Size Body Weight Female Imaging Three-Dimensional Photogrammetry Seals Earless Specific Gravity General Science & Technology |
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 ... |
author2 |
Ropert-Coudert, Yan |
format |
Article in Journal/Newspaper |
author |
Beltran, Roxanne S Ruscher-Hill, Brandi Kirkham, Amy L Burns, Jennifer M |
author_facet |
Beltran, Roxanne S Ruscher-Hill, Brandi Kirkham, Amy L Burns, Jennifer M |
author_sort |
Beltran, Roxanne S |
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 |
eScholarship, University of California |
publishDate |
2018 |
url |
https://escholarship.org/uc/item/11g8z7g9 |
op_coverage |
e0189865 |
genre |
Weddell Seals |
genre_facet |
Weddell Seals |
op_source |
PLOS ONE, vol 13, iss 1 |
op_relation |
qt11g8z7g9 https://escholarship.org/uc/item/11g8z7g9 |
op_rights |
public |
_version_ |
1781707771127791616 |