10.5061/DRYAD.GTHT76HN6
Shero, Michelle
0000-0003-4633-5351
Woods Hole Oceanographic Institution
Dale, Julian
Duke University
Seymour, Alexander
Duke University
Hammill, Mike
Department of Fisheries and Oceans Canada
Mosnier, Arnaud
Department of Fisheries and Oceans Canada
Mongrain, Samuel
Department of Fisheries and Oceans Canada
Johnston, David
0000-0003-2424-036X
Duke University
Tracking wildlife energy dynamics with unoccupied aircraft systems and
3-dimensional photogrammetry
Dryad
dataset
2021
body volume
drone
grey seal
Halichoerus grypus
Mass
Morphometrics
3D morphometrics
body morphometrics
photogrammetry
Structure-from-Motion (SfM) photogrammetry
pinniped
National Geographic Society
https://ror.org/04bqh5m06
64226R-19
Department of Fisheries and Oceans Canada*
WHOI Innovative Research and Development*
Oak Foundation
https://ror.org/006ss0h52
Department of Fisheries and Oceans Canada
WHOI Innovative Research and Development
2021-09-26T00:00:00Z
2021-09-26T00:00:00Z
en
https://doi.org/10.1111/2041-210X.13719
108299 bytes
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CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
We present a novel application using unoccupied aircraft systems (UAS;
drones) for structure-from-motion three-dimensional (3-D) photogrammetry
of multiple, free-ranging animals simultaneously. Pinnipeds reliably
haul-out on shore for pupping and breeding each year, accompanied by
dramatic female-to-pup mass transfer over a short lactation period and
males lose mass while defending mating territories. This provides a
tractable study system for validating the use of UAS as a non-invasive
tool for tracking energy dynamics in wild populations. UAS imagery of grey
seals (Halichoerus grypus) was collected at Saddle Island, Nova Scotia. A
multirotor UAS was piloted in 360-degree orbits around relatively dense
animal aggregations and georeferenced images were used for construction of
a 3-D point cloud, orthomosaic, and Digital Surface Model for animal
volumetric measurements. Directly following UAS survey, a subset of adult
females were hand-measured (morphometrics, blubber depth, n=21 handlings
[15 were unique animals]) and female-pup pairs were weighed (adult
females: n=32 [24]; pups: n=33 [23]) to validate that UAS 3-D
photogrammetric models provided accurate animal volume and mass estimates.
UAS two-dimensional body length measurements were sensitive to animal
recumbency and posture. The new UAS 3-D photogrammetric method overcame
these constraints, and aerial-derived body volume measurements were
equivalent to those collected from the ground. UAS body volume
measurements precisely predicted ‘true’ body mass (mean-absolute-error,
adult female: 8 kg, 2.1% body mass; pup: 4.1 kg, 9.8%), and exhibited a
stronger relationship with total body mass than with blubber volume. The
method was applied to 673 free-ranging animals to characterize volume and
mass dynamics across lactation and breeding for a much larger sample size
than would be possible using traditional ground methods. Indeed, 1-46
animals (mean±SE: 9.2±1.2) were modeled concurrently within the focal area
of a UAS flight. Application of the method also captured significant
inter-annual variation in body volume/mass dynamics, and female-to-pup
energy transfer efficiencies were lower when there was low sea-ice extent.
The UAS 3-D photogrammetric method presented in this study is likely to be
broadly applicable to other species, and the ability to measure whole
groups of free-ranging animals at once makes strides towards ‘weighing
populations’.
README_SheroMethodsEcolEvol2021.xlsx contains metadata for each of the
following datasheets: Shero_MEE2021_masses_volumes.csv file contains
ground acquired mass and animal body volume measurements, as well as the
UAS-derived volumetric measurements for each animal. Animal posture,
terrain, and flight characteristics are also provided.
Shero_MEE2021_larger_area_surveys.csv file contains UAS body volume
measurements collected from larger area surveys. Note that under Age
Cagetory, Adult female = "AF", Pup = "P",
Unaccompanied pup = "UP", and Male = "M".
Shero_MEE2021_Alta6_flight_specs.csv file contains information on flight
attributes for the FreeFly Alta 6 multirotor UAS projects used in the
manuscript. Shero_MEE2021_Morphs_datasheet.csv file contains original
ground morphometrics measurements that were used to calculate animal total
body volume using elliptical truncated cones.
Shero_MEE2021_supplemental_DJIPhantom_flightspecs.csv contains flight
attributes of the DJI Phantom 4 Pro V2 flights used in the supplemental
materials. Shero_MEE2021_supplemental_DJIPhantom_animal_volumes.csv
contains UAS volumetric measurements of animals imaged with the DJI
Phantom Pro V2 UAS.