[MARMAM] New publication on the use of drone photogrammetry to estimate elephant seal mass

Diana Alvarado dicalvar at ucsc.edu
Wed Jul 15 15:29:47 PDT 2020

Dear all, 

My co-authors and I are pleased to announce the Early View of our publication in Marine Mammal Science:

Alvarado DC, Robinson PW, Frasson NC, Costa DP, Beltran RS. Calibration of aerial photogrammetry to estimate elephant seal mass. Mar Mam Sci. 2020;1-9. https://doi.org/10.1111/mms.12714 <https://doi.org/10.1111/mms.12714>


Body mass measurements can provide important insights into the physiology and foraging ecology of marine mammals. Unmanned aerial system (UAS) photogrammetry offers a method that is safer for both animals and researchers and is logistically simpler than traditional weighing methods.  Our objectives were: 1) to evaluate the accuracy of UAS photogrammetry for estimating the mass of adult female northern elephant seals and 2) to examine the effect of body position on mass estimates obtained using UAS.  We analyzed a series of UAS images of 22 adult female northern elephant seals (Mirounga angustirostris) of known mass at Año Nuevo Reserve (San Mateo County, California, USA). Complete body areas (hereafter, footprint areas, measured in m2) of seals in a dorsal (laying on ventral surface, N=45) or lateral (laying on side, N=7) body position were measured in ImageJ using the standard polygon area selection tool and compared to mass measurements. Linear regressions of measured mass against footprint suggest that mass is more strongly related to dorsal footprints (R2= 0.895, N=45) than lateral footprints (R2= 0.822, N=7). Residual error ranged from -68.7 to +69.3 kg and seal mass was estimated with a mean error of 7.7 kg, or 2.4%, of total body mass. With the predictive models found, UAS photogrammetry will allow us to expand our knowledge of seasonal energetic intake and expenditure, especially in large-bodied and fully aquatic species in remote areas. Mass measurements can inform ecosystem-based resource management by providing information about the inter-annual productivity of the ocean environment and in turn individual, population, and ecosystem-level health in marine mammals.

The publication can be found at this link: http://dx.doi.org/10.1111/mms.12714 <http://dx.doi.org/10.1111/mms.12714>

PDF requests can be sent to dicalvar at ucsc.edu <mailto:dicalvar at ucsc.edu>

Best regards,
Diana Alvarado
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