Validation of the photogrammetric method to assess body condition of an odontocete, the shortfinned pilot whale Globicephala macrorhynchus

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 620:185-200 (2019) - DOI: https://doi.org/10.3354/meps12971 Validation of the photogrammetric method to assess body condition of an odontocete, the shortfinned pilot whale Globicephala macrorhynchus S. R. Noren1,*, L. Schwarz1, K. Chase2, K. Aldrich3, K. McMahon-Van Oss3, J. St. Leger2 1Intitute of Marine Science, University of California Santa Cruz, Santa Cruz, CA 95060, USA 2SeaWorld San Diego, San Diego, CA 92109, USA 3SeaWorld Orlando, Orlando, FL 32821, USA *Corresponding author: snoren@ucsc.edu ABSTRACT: Validated metrics to monitor body condition of free-ranging animals are critical to track population stability. We tested repeatability and reliability of body width and body length measurements taken from overhead photographs and validated the assumptions upon which the photogrammetric method to monitor cetacean body condition are based. Short-finned pilot whales Globicephala macrorhynchus served as models. Variability was low for multiple measurements taken from 1 photograph and across photographs of the same animal; standard deviations represented 1.2 ± 1.2% and 2.5 ± 1.3% of mean estimates, respectively. To account for body length variations across whales, we calculated mass, width, and blubber indexes as the residual values of these variables regressed against length. Across the sites examined (anterior pectoral fin, anterior dorsal fin, and posterior dorsal fin), only photogrammetric body width at the posterior dorsal fin site showed consistent significant positive relationships with measured condition indexes (i.e. width and blubber index slope = 0.10, p = 0.005; width and mass index slope = 18.1, p < 0.01). Moreover, only the body width to body length ratio at this site predicted mass index (slope = 3105, p = 0.05). Thus, changes in photogrammetrically measured body width posterior of the dorsal fin at approximately 47% of total body length from the rostrum are related to changes in underlying blubber thickness and body mass. The width:length ratio at this site can be used to monitor condition. Additional studies are warranted to determine if body width at this site reliably predicts condition across odontocete species with varying body morphologies. KEY WORDS: Photogrammetry · Body condition · Blubber · Pilot whale · Odontocete · Disturbance Full text in pdf format PreviousNextCite this article as: Noren SR, Schwarz L, Chase K, Aldrich K, McMahon-Van Oss K, St Leger J (2019) Validation of the photogrammetric method to assess body condition of an odontocete, the shortfinned pilot whale Globicephala macrorhynchus. Mar Ecol Prog Ser 620:185-200. https://doi.org/10.3354/meps12971 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 620. Online publication date: June 18, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.