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Comparing Uncertainty Associated With 1-, 2-, and 3D Aerial Photogrammetry-Based Body Condition Measurements of Baleen Whales

Publication ,  Journal Article
Bierlich, KC; Hewitt, J; Bird, CN; Schick, RS; Friedlaender, A; Torres, LG; Dale, J; Goldbogen, J; Read, AJ; Calambokidis, J; Johnston, DW
Published in: Frontiers in Marine Science
November 26, 2021

Body condition is a crucial and indicative measure of an animal’s fitness, reflecting overall foraging success, habitat quality, and balance between energy intake and energetic investment toward growth, maintenance, and reproduction. Recently, drone-based photogrammetry has provided new opportunities to obtain body condition estimates of baleen whales in one, two or three dimensions (1D, 2D, and 3D, respectively) – a single width, a projected dorsal surface area, or a body volume measure, respectively. However, no study to date has yet compared variation among these methods and described how measurement uncertainty scales across these dimensions. This associated uncertainty may affect inference derived from these measurements, which can lead to misinterpretation of data, and lack of comparison across body condition measurements restricts comparison of results between studies. Here we develop a Bayesian statistical model using known-sized calibration objects to predict the length and width measurements of unknown-sized objects (e.g., a whale). We use the fitted model to predict and compare uncertainty associated with 1D, 2D, and 3D photogrammetry-based body condition measurements of blue, humpback, and Antarctic minke whales – three species of baleen whales with a range of body sizes. The model outputs a posterior predictive distribution of body condition measurements and allows for the construction of highest posterior density intervals to define measurement uncertainty. We find that uncertainty does not scale linearly across multi-dimensional measurements, with 2D and 3D uncertainty increasing by a factor of 1.45 and 1.76 compared to 1D, respectively. Each standardized body condition measurement is highly correlated with one another, yet 2D body area index (BAI) accounts for potential variation along the body for each species and was the most precise body condition metric. We hope this study will serve as a guide to help researchers select the most appropriate body condition measurement for their purposes and allow them to incorporate photogrammetric uncertainty associated with these measurements which, in turn, will facilitate comparison of results across studies.

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Published In

Frontiers in Marine Science

DOI

EISSN

2296-7745

Publication Date

November 26, 2021

Volume

8

Related Subject Headings

  • 3708 Oceanography
  • 3705 Geology
  • 3103 Ecology
  • 0602 Ecology
  • 0405 Oceanography
 

Citation

APA
Chicago
ICMJE
MLA
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Bierlich, K. C., Hewitt, J., Bird, C. N., Schick, R. S., Friedlaender, A., Torres, L. G., … Johnston, D. W. (2021). Comparing Uncertainty Associated With 1-, 2-, and 3D Aerial Photogrammetry-Based Body Condition Measurements of Baleen Whales. Frontiers in Marine Science, 8. https://doi.org/10.3389/fmars.2021.749943
Bierlich, K. C., J. Hewitt, C. N. Bird, R. S. Schick, A. Friedlaender, L. G. Torres, J. Dale, et al. “Comparing Uncertainty Associated With 1-, 2-, and 3D Aerial Photogrammetry-Based Body Condition Measurements of Baleen Whales.” Frontiers in Marine Science 8 (November 26, 2021). https://doi.org/10.3389/fmars.2021.749943.
Bierlich KC, Hewitt J, Bird CN, Schick RS, Friedlaender A, Torres LG, et al. Comparing Uncertainty Associated With 1-, 2-, and 3D Aerial Photogrammetry-Based Body Condition Measurements of Baleen Whales. Frontiers in Marine Science. 2021 Nov 26;8.
Bierlich, K. C., et al. “Comparing Uncertainty Associated With 1-, 2-, and 3D Aerial Photogrammetry-Based Body Condition Measurements of Baleen Whales.” Frontiers in Marine Science, vol. 8, Nov. 2021. Scopus, doi:10.3389/fmars.2021.749943.
Bierlich KC, Hewitt J, Bird CN, Schick RS, Friedlaender A, Torres LG, Dale J, Goldbogen J, Read AJ, Calambokidis J, Johnston DW. Comparing Uncertainty Associated With 1-, 2-, and 3D Aerial Photogrammetry-Based Body Condition Measurements of Baleen Whales. Frontiers in Marine Science. 2021 Nov 26;8.

Published In

Frontiers in Marine Science

DOI

EISSN

2296-7745

Publication Date

November 26, 2021

Volume

8

Related Subject Headings

  • 3708 Oceanography
  • 3705 Geology
  • 3103 Ecology
  • 0602 Ecology
  • 0405 Oceanography