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The APH-22 hexacopter (Aerial Imaging Solutions, Old Lyme, CT) that was used to fl y 60 successful missions to collect vertical photogrammetry images of killer whales at sea. Here shown with the Olympus E-PM2 camera and interchangeable lens system; the camera mounts on the underside of the hexacopter to be downward-facing. 

The APH-22 hexacopter (Aerial Imaging Solutions, Old Lyme, CT) that was used to fl y 60 successful missions to collect vertical photogrammetry images of killer whales at sea. Here shown with the Olympus E-PM2 camera and interchangeable lens system; the camera mounts on the underside of the hexacopter to be downward-facing. 

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Conventional aircraft have been used for photogrammetry studies of free-ranging whales, but are often not practical in remote regions or not affordable. Here we report on the use of a small, unmanned hexacopter (APH-22; Aerial Imaging Solutions) as an alternative method for collecting photographs to measure killer whales (Orcinus orca) at sea. We d...

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... aircraft have been successfully used for photogrammetry studies of free-ranging whales. Fixed-wing planes and helicopters have been used to obtain vertical photographs from directly above whales, from which shape profiles can be measured to assess body condition to infer nutritional status and pregnancy (e.g., Perryman and Lynn 2002). When combined with information on scale (= altitude/focal length), these images can also be used to estimate absolute length (e.g., Pitman et al. 2007) and monitor growth trends (e.g., Fearnbach et al. 2011). However, aircraft operations are often not practical in remote regions, and not affordable under typical research budgets, and therefore this technique has not been widely used. Here we report on a recent project using a small unmanned aerial system (UAS) as an alternative method for successfully obtaining photogrammetry images of killer whales ( Orcinus orca ) at sea. Our study area was around Vancouver Island, off the British Columbia coastline of western Canada. Previously, we used a helicopter to measure “ Southern Resident ” killer whales in the more accessible waters off Southern Vancouver Island (Fearnbach et al. 2011), but required an alternative approach to obtain comparative measurements from the “ Northern Resident ” population in the more remote area at the north of the island. We chose to use a small multi-rotor UAS because vertical takeoff and landing (VTOL) capability was required to operate from a small boat, and we required stability in flight for photographic operations. We chose a small (1.2 kg dry weight without payload; 82 cm wingspan) hexacopter that was recently used in Antarctica to obtain photographs for counting seals and penguins, and to estimate the size of leopard seals onshore (Goebel et al. 2015). This UAS platform has been proven to have the endurance and performance characteristics to conduct successful photographic missions in a windy environment, and to create a limited sound footprint that does not dis- turb wildlife. The APH-22 hexacopter (Aerial Imaging Solutions, Old Lyme, CT; Fig. 1) is described in Goebel et al. (2015); however, one key modification to firmware was required for operating from a boat, namely, the ability to store a motionless calibration of the gyro sensors made on land and recall these gyro offsets from non-volatile memory when on the boat. This enabled the hexacopter to maintain stable flight attitude, even when launched from a moving platform at sea. We successfully deployed and retrieved the hexacopter by hand during 60 flight missions launched from the upper deck of an 8.2 m SeaSport boat (Fig. 2). This procedure proved to be safe and repeatable, because of the stable flight and low weight of the hexacopter; the only payload was a camera (Olympus E-PM2, 0.23 kg; Olympus M.Zuiko 25 mm F1.8 lens, 0.13 kg) and hexacopter battery (QuadroPower 6200 mAh Lipo Flat; 0.58 kg). Wind speeds were less than 5 m/s (10 knots) during all flights, as we chose to only fly when a smooth sea state would enable detailed images of whales beneath the surface. The average duration of the 60 flights was 13.2 min (max = 15.7 min). These marine flights were conservatively ended well in advance of battery limitations — the APH-22 has been flown for >25 min during test flights with the same battery. The total distance covered during a flight averaged 1350 m (max = 2480 m), but the distance to the pilot was smaller (typically <200 m) as the boat was continuously maneuvered to enable line-of-sight piloting of the hexacopter and facilitate positioning over whales. The hexacopter was controlled by the pilot using a radio link (2.4 GHz), and we did not experience any loss of link during the 13.25 h of total flying. Finer-scale positioning of the hexacopter above whales was accomplished through guidance from a ground station operator who viewed live analog video captured by the onboard camera and transmitted to a portable monitor on the boat using a 5.8 GHz link. When whales were in the frame, the pilot used a remote link to trigger the cap- ture of high-resolution (12.3 MP) still images on the camera ’ s flash memory. The ground station also displayed telemetry information (910 MHz link), which enabled monitoring of altitude, flight time, and battery levels for flight management. We were successful at positioning the hexacopter directly above groups of killer whales, and obtained a total of 18920 still images from an altitude of 35 – 40 m. We did not observe any behavioral responses from the whales during any of the flights, and they likely were not aware of the small hexacopter at these altitudes. The 25 mm lens we used is considered “ normal ” for the Micro Four-Thirds sensor of the E-PM2 camera, in that the focal length is equal to the diagonal of a square formed by the long dimension of the sensor, and therefore photogrammetry measurements were possible across the full extent of a flat and undistorted field of view. Previous resolution tests over a standard medium contrast (8:1) resolution target (RST-704, series C) showed that we had a ground-resolved distance of <1.8 cm using the 25 mm lens at an altitude of 50 m, which improved further to <1.4 cm at our standard altitude of 35 m. Our images of the whales clearly showed that this expected resolution was rea- lized in photographs at sea: notably, we could resolve differences in natural markings to identify individual whales using images of their saddle patch pigmentation (Fig. 3), which allowed us to link measurements to whales of known age and sex (e.g., Fearnbach et al. 2011). One of the key requirements of our photogrammetry system is the ability to obtain whale length and width profiles on a real scale. Measurements from the images in pixels can be converted to a true measurement using the known longitudinal dimension of the camera sensor and the number of pixels comprising this known width, and these can then be scaled to true lengths using the measured altitude and the focal length of the lens (e.g., Fearnbach et al. 2011). The flight controllers on the hexacopter used a Freescale MPX4115A absolute air pressure sensor, which has on-chip temperature compensation, for altitude measurements. We calculated the altitude of the hexacopter at 1 s intervals by applying the standard altitude equation to the difference between the pressure while flying and the pressure at takeoff, with a known takeoff height above sea level. Onboard measures of altitude were validated by scale calculations of the distance between points of known separation (6.4 m = approximate whale length) on the deck of our research vessel, measured from photographs taken at our standard photogrammetry altitudes. Using 16 different calibration photographs from calculated altitudes of 35 – 38 m, the average bias was − 0.05 m (standard deviation = 0.29 m), representing <1% of the total length of the boat. This indicated the ability to monitor absolute size and growth of whales with precision, which is demonstrated in Fig. 4 by estimated length differences among seven whales of varying ages within the “ I16 matriline ” (family group) of killer whales. These whales ranged in ages between a first year calf and a 45 year old adult female at the time of the photograph in 2014, with estimated lengths ranging from 2.6 to 5.8 m from this particular image. At the time of writing, work is underway to identify and measure all the whales in this large photographic sample, and further data collection is planned to quantitatively monitor individual whale growth and body condition into the future. This first, and very successful, field effort at sea has demonstrated the APH-22 hexacopter to have great utility for collecting photogrammetry images to fill key scientific data gaps about free ranging whales. It is a small and portable aircraft with VTOL capability that enables safe deployment and retrieval from even small boat platforms, and therefore enables aerial photogrammetry in remote locations where conventional aircraft are impractical. It is quiet and stable in flight, and can therefore be flown at relatively low altitudes without disturbing whales. As a result, we can obtain high-resolution images that are sharp enough to differentiate individual whales using natural markings, with precise altitude to enable quantitative measurements. We anticipate that these advantageous features will provide a cost-effective option for studies of wildlife populations in general, not just whales. Hexacopter flights were authorized by a Special Flight Operations Certificate from Transport Canada and approaches to whales by both the boat and hexacopter were authorized by Research License issued by Fisheries and Oceans Canada (2014-5 SARA-327). J. Borrowman helped with field logistics, C. Crossman facilitated project planning, and J. Towers assisted with identifying known whales from aerial images. Field costs were supported by a grant from the Seaworld & Busch Gardens Conservation Fund. Development of the hexacopter was performed under a grant from NOAA ’ s Office of Marine and Aviation Operations, and through the support of Commander M.J. Silah, ...

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... By adjusting the camera angle (−27°of inclination), altitude (at a height of 50 m), and orientation (move in a lateral position) and UAV speed (40 km/h), the detection capability of marine megafauna can be enhanced, which can improve the efficiency of monitoring sea turtles, seabirds, large fish, and especially small cetaceans (Jonathas et al., 2021). By flying at an altitude of 35-40 m, important information about the size, health and behavior of marine animals can be gathered (Durban et al., 2015;Pomeroy et al., 2015;Vincent et al., 2020). Given that different marine animals respond differently to drones (Brisson-Curadeau et al., 2017;Christiansen et al., 2020a;Christiansen et al., 2016b;Edney and Wood, 2021;Goldbogen et al., 2019;Ramos et al., 2018;Rümmler et al., 2018;Smith et al., 2016), flight plans need to minimize drone disturbance to wildlife by considering not only the target species but also the more vulnerable or sensitive species that may be encountered (Hodgson and Koh, 2016;Vincent et al., 2020). ...
... In addition, even within species, physiological or behavioral responses to drones vary across different life history periods (breeding stages are more sensitive to disturbance) or group sizes (larger groups appear to be less susceptible to disturbance); thus, the flight altitude of an appropriate type of drone needs to be optimized based on the status of the subject and the targeted objectives of the study (Edney and Wood, 2021;Vincent et al., 2020;Weimerskirch et al., 2018). Regarding the use of UAV remote sensing images for photographic identification, representative features and scars may be distorted or obscured due to interference from factors such as ripples, light and turbidity (Joyce et al., 2018;Landeo-Yauri et al., 2020); for photogrammetry of animals (Christiansen et al., 2018;Durban et al., 2016), it is challenging to depict the entire body of an animal in a straight-line position and near the water surface (Durban et al., 2015). In these cases, deep learning techniques can enhance photogrammetric workflows aimed at rapid identification and accurate measurement of marine animals in aerial images (Gray et al., 2019); the use of aerial video allows the selection of frame times, features, and animal locations and is also a promising option (Jonathas et al., 2021;Vincent et al., 2020). ...
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... A broad range of marine megafauna has been studied using drones, including sea turtles [3][4][5][6][7], cetaceans [8][9][10][11] and elasmobranchs (sharks and rays) [12,13], and multiple species have also been surveyed simultaneously [14][15][16][17][18][19][20][21][22]. Despite their popularity in elasmobranch research, a recent review highlighted the underutilization of drone technology in batoid (ray) research compared to sharks [13]. ...
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... Unmanned aerial vehicles (hereafter "drones") are ideal platforms for low-cost and non-invasive morphometric measurements of marine mammal body size because of their capacity for precision flight, and the ability to carry numerous sensor packages for scaling and observation (Smith et al. 2016;Schofield et al. 2019). Drone-based photogrammetry has been applied to investigating the health, body condition, energetics, and reproductive biology of large-bodied marine animal species including pinnipeds (Allan et al. 2019), killer whales (Orcinus orca) (Durban et al. 2015), blue whales (Balaenoptera musculus) (Durban et al. 2016), and humpback whales (Megaptera novaeangliae) (Dawson et al. 2017;Christiansen et al. 2019;Aoki et al. 2021). These studies can provide compelling data needed for identifying the causes of population impacts such as mortality events. ...
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... Photoidentification of individual dolphins near trawlers and away from trawlers can help assess the influence of trawling on aspects of demography and social organization (Chilvers and Corkeron 2001;Ansman et al. 2012;Genov et al. 2019), as well as make possible the characterization and evaluation of cultural transmission (Kovacs et al. 2017). Unoccupied Aerial Vehicles (UAVs) operated from independent boats or from trawlers by qualified and dedicated researchers may generate quality data (Durban et al. 2015;Christiansen et al. 2016;Orbach et al. 2020;Ramos et al. 2021). UAVs can also be deployed to collect biological samples (e.g. of dolphin blow to assess microbial and viral communities and cortisol levels; Raverty et al. 2017;Burgess et al. 2018;Centelleghe et al. 2020). ...
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... However, drones now offer the ability to track multiple individuals simultaneously (Durban et al., 2022). While this new source of movement data can achieve a high spatial precision (Dawson et al., 2017;Durban et al., 2015Durban et al., , 2022, it sometimes introduces complex labeling issues due to the observation process. When animals that cannot be uniquely identified disappear out of a drone's active field of view for sustained intervals of time, they are typically assigned a new label upon reappearance. ...
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The social structure of an animal population can often influence movement and inform researchers on a species' behavioral tendencies. Animal social networks can be studied through movement data; however, modern sources of data can have identification issues that result in multiply-labeled individuals. Since all available social movement models rely on unique labels, we extend an existing Bayesian hierarchical movement model in a way that makes use of a latent social network and accommodates multiply-labeled movement data (MLMD). We apply our model to drone-measured movement data from Risso's dolphins (Grampus griseus) and estimate the effects of sonar exposure on the dolphins' social structure. Our proposed framework can be applied to MLMD for various social movement applications.
... Even if behaviour is not the focus of a study, the permanent imagery provides the potential for it to be subsequently used for a variety of other behavioural objectives. Furthermore, although not reported here, the drone imagery can be used for diverse post-processing data mining, such as identifying the precise number of neonates, calves, and juveniles, and for identifying sexual maturity, mother/calf pairs, body shape, and nutritive condition of all dolphins in a group [21][22][23]. ...
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Generating accurate estimates of group sizes or behaviours of cetaceans from boat-based surveys can be challenging because much of their activity occurs below the water surface and observations are distorted by horizontal perspectives. Automated observation using drones is an emerging research tool for animal behavioural investigations. However, drone-based and boat-based survey methods have not been quantitatively compared for small, highly mobile cetaceans, such as Delphinidae. Here, we conduct paired concurrent boat-based and drone-based surveys, measuring the number of individuals in 21 groups and the behaviour within 13 groups of bottlenose dolphin (Tursiops truncatus). We additionally assessed the ability to detect behaviour events by the drone that would not be detectable from the boat. Drone-derived abundance counts detected 26.4% more individuals per group on average than boat-based counts (p = 0.003). Drone-based behaviour observations detected travelling 55.2% more frequently and association in subgroups 80.4% more frequently than boat-based observations (p < 0.001 for both comparisons). Whereas foraging was recorded 58.3% and resting 15.1% less frequently by the drone than by boat-based surveys, respectively (p = 0.014 and 0.024). A considerable number of underwater behaviours ranging from individual play activities to intra- and inter-species interactions (including those with humans) were observed from the drone that could not be detected from the boat. Our findings demonstrate that drone surveys can improve the accuracy of population counts and behavioural data for small cetaceans and the magnitude of the discrepancies between the two methods highlights the need for cautious interpretation of studies that have relied on boat-derived data.
... This relationship was used to convert measurements of the distance from rostrum to tail notch of each whale, from pixels to meters. Details about the UASs, the piloting methods and the accuracy of measurements can be found in Table S1 and in previously published papers (Durban et al., 2015(Durban et al., , 2016Gough et al., 2019;Torres and Bierlich, 2020). We measured the body lengths of 93 individual whales from all seven species (Table 1). ...
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... UAS have been utilized in many aspects of marine science and conservation as a non-invasive method for sampling over the large scales often needed to collect data on mobile vertebrates (Brooke et al., 2016;Fiori et al., 2017;Johnston, 2019;Seymour et al., 2017). Small, portable and affordable UAS have been applied to study abundance, distribution, movement and behaviour (Durban et al., 2015;Fiori et al., 2017;Hodgson et al., 2013;Raoult et al., 2020). UAS also allow the collection of whole-body measurements and can be calibrated with data on altitude to convert to useful body measurements (Bierlich et al., 2021;Burnett et al., 2019;Dawson et al., 2017). ...
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Data on sex ratios, age classes, reproductive success and health status are key metrics to manage populations, yet can be difficult to collect in wild cetacean populations. Long‐term individual‐based studies provide a unique opportunity to apply unoccupied aerial system (UAS) photogrammetry to non‐invasively measure body morphometrics of individuals with known life history information. The aims of this study were (1) to compare length measurements from UAS photogrammetry with laser photogrammetry and (2) to explore whether UAS measurements of body width could be used to remotely determine pregnancy status, sex or age class in a well‐studied bottlenose dolphin population in Scotland. We carried out five boat‐based surveys in July and August 2017, with concurrent photo‐identification, UAS and laser photogrammetry. Photographs were measured using bespoke programmes, MorphMetriX for UAS photos and a Zooniverse project for laser photos. In total 64 dolphins were identified using photo‐ID, 54 of which had concurrent UAS body length and 47 with laser body length measurements. We also measured body widths at 10% increments from 10% to 90% of body length for 48 individuals of known sex, age class and/or pregnancy status. There was no significant difference in the length of individuals measured with UAS and laser photogrammetry. Discriminant analyses of the body width–length (WL) ratios expected to change during pregnancy, correctly assigned pregnancy status for 14 of the 15 females of known pregnancy status. Only one pregnant female was incorrectly assigned as not pregnant. However, our results showed that length and body width cannot accurately allocate these bottlenose dolphins to sex or age class using photogrammetry techniques alone. The present study illustrates that UAS and laser photogrammetry measurements are comparable for small cetaceans and demonstrates that UAS measurements of body WL ratio can accurately assign pregnancy status in bottlenose dolphins. Long‐term individual‐based studies provide a unique opportunity to apply unoccupied aerial system (UAS) photogrammetry to non‐invasively measure body morphometrics of individuals with known life history information. Our study illustrates that UAS and laser photogrammetry measurements are comparable in small cetaceans, and demonstrates that UAS measurements of body width‐length ratio can accurately assign pregnancy status in bottlenose dolphins.
... Finally, the recent proliferation of unmanned aerial systems (UAS) provides promising new tools for wildlife monitoring and research, improving photogrammetric quality and simplifying image postprocessing, and has already been proven useful in killer whales (Orcinus orca, Durban et al., 2015), leopard seals (Hydrurga leptonyx, Krause et al., 2017), and a variety of whale species (Christiansen et al., 2019;Durban et al., 2016). The increasing availability and growing performance of imaging technology like 3D scanners, also provides new opportunities for measuring morphology (Tsuboi et al., 2020) and has been employed in many fields (Allegra et al., 2017). ...
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Direct measures of body mass of marine mammals are logistically complicated to obtain even for pinnipeds. An alternative method for mass estimation based on 3D imaging technology and automated processing algorithms, was tested in southern elephant seals (Mirounga leonina). Two models of artificial neural networks (ANN)—nonlinear neural network and self‐organizing maps—were trained to compute the volume and to estimate the mass of the digital models, previously obtained by scanning individuals with an infrared light sensor. Body mass estimates were as accurate (mean % error = 4.4) as estimates in previous photogrammetry studies in southern elephant seals and the mass predictive ability of the trained ANN was higher (99% of the variance explained) than other predictive models using photogrammetry in pinniped studies. While this method has proven to produce accurate body mass estimates, it also overcame some of the constraints of other indirect techniques, avoiding animal disturbance caused by physical restraint or chemical immobilization, minimizing risks, and capitalizing on the time working in the field. The results of these estimations were promising, which shows that the proposed methodology can provide adequate results with lower logistic and computational requirements.
... In 17 research articles, drone flights were used to collect biological data, which were body condition in pinnipeds (Allan et al. 2019;Hodgson et al. 2020) and cetaceans Krause et al. 2017), individual markings (Durban et al. 2015) and biochemical vital signs in cetaceans (Horton et al. 2019), morphometric measurements in pinnipeds (Pomeroy et al. 2015), cetaceans (Christiansen et al. 2018(Christiansen et al. , 2019 and bony fishes (Jech et al. 2020), vocalisations in bats (Fu et al. 2018;Kloepper et al. 2018), and nest contents and survival in birds of prey (Potapov et al. 2013;Junda et al. 2015), aquatic birds (Sardà-Palomera et al. 2017;Lachman 2020), and passerines (Weissensteiner et al. 2015). A further seven research articles involved drone flights to collect samples from animals, which were all relating to blow sampling from cetaceans (Acevedo-Whitehouse et al. 2010;Apprill et al. 2017;Pirotta et al. 2017;Geoghegan et al. 2018;Nelson et al. 2019;Raudino et al. 2019;Centelleghe et al. 2020). ...
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Drones or unoccupied aerial vehicles are rapidly being used for a spectrum of applications, including replacing traditional occupied aircraft as a means of approaching wildlife from the air. Though less intrusive to wildlife than occupied aircraft, drones can still cause varying levels of disturbance. Policies and protocols to guide lowest-impact drone flights are most likely to succeed if considerations are derived from knowledge from scientific literature. This study examines trends in the scientific literature on using drones to approach wildlife between 2000 and 2020, specifically in relation to the type of publications, scientific journals works are published in, the purposes of drone flights reported, taxa studied, and locations of studies. From 223 publications, we observed a large increase in relevant scientific literature, the majority of which were peer-reviewed articles published across 87 scientific journals. The largest proportions of peer-reviewed research articles related to aquatic mammals or aquatic birds, and the use or trial of drone flights for conducting population surveys, animal detection or investigations of animal responses to drone flights. The largest proportion of articles were studies conducted in North America and Australia. Since animal responses to drone flights vary between taxa, populations, and geographic locations, we encourage further growth in the volume of relevant scientific literature needed to inform policies and protocols for specific taxa and/or locations, particularly where knowledge gaps exist.