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A) An example of desired aerial photograph of humpback whales captured by a unmanned aerial vehicle that was used in analyses. The whale is lying flat at the surface, dorsal side facing up, with a straight body axis and peduncle (nonarching). (B) Position of measurement sites of humpback whales recorded in this study. For clarity, only width (W) measurement sites located at 10% increments along the body axis are shown.
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An animal's body condition will affect its survival and reproductive success, which influences population dynamics. Despite its importance, relatively little is known about the body condition of large whales and its relationship to reproduction. We assessed the body condition of humpback whales (Megaptera novaeangliae) at a breeding/resting ground...
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Context 1
... providing the UAV operator with direct feed from the GoPro camera, was used to cor- rect the position of the UAV above the whale and also confirm that photographs of adequate quality had been obtained. Desired photographs were of a whale lying flat at the surface, dorsal side facing up, with a straight body axis and peduncle (that was nonarching; Fig. 2). The UAV was then flown to an altitude of 80-120 m, while the research vessel moved closer to the whale until both the whale and the boat were visible in the same photograph. The size of the research vessel was then used to scale the photograph (similar to Whitehead and Payne 1978). Once the scale photograph had been obtained, the UAV ...
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... 2003, Miller et al. 2012), using a custom-written script in R (R Core Team 2014; Appendix S1 and Data S1). Length mea- surements (in pixels) included distance from the tip of the rostrum to: the notch of the tail fluke; the end of the dorsal fin; the position of the eyes (measured along the body axis of the whale); the beginning of the tail fluke (Fig. 2). The width of the whale (in pixels), measured perpendicular to the body axis, was measured at 5% intervals along the entire body of the whale, not including 0 and 100% of the body length (19 measurements in total), and also between the eyes. The relative measurements of the whale (in pixels) were converted to absolute measurements (in ...
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... 1). Over this 44-d period, we spent 26 d on the water, equaling 186 h of research effort (Fig. 1). After ini- tial filtering of photographs based on body posi- tion (removing laterally curved, arched, and animals rolling on their side) and picture quality (Appendix S2: Fig. S1 [m]: mean = 12.20, SD = 0.98, min = 10.77, max = 14.73) (Appendix S2: Fig. S2). Photograph identification records indicated that no individual was measured more than once during the study period. Hence, the body condi- tion data represent a cross-sectional sample of the population and not repeated measurements of the same individuals. We did not observe any visual behavioral responses of the whales toward the ...
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Citations
... During their stay in the breeding area, humpback whale calves undergo remarkable growth and development. They gain about 3 cm in length per day (Christiansen et al., 2016), for a daily weight gain estimated to be about 30 kg (Oftedal, 1997). Their diving and swimming abilities also improve rapidly (Cartwright & Sullivan, 2009;Ejrnaes & Sprogis, 2021;Huetz et al., 2022). ...
... Their diving and swimming abilities also improve rapidly (Cartwright & Sullivan, 2009;Ejrnaes & Sprogis, 2021;Huetz et al., 2022). The cost associated with sustaining such rapid growth and development of the calf in the breeding ground is considerable for the mother, as indicated by Christiansen et al. (2016), who observed an elevated rate of body condition decline in lactating females compared to nonlactating adults. In these contexts, and with the alarming increase in human coastal activities that impact whales, how the mother and calf organize their activities in the breeding ground is of particular interest to gain insight into energy allocation, the calf's needs, and the level of dependence of the calf on its mother, and to understand the potential impact of disturbances from anthropic activities during the critical phase of calf's development. ...
... Optimizing the time spent at a low activity level minimizes the decline in body condition. It thus ensures sufficient milk production to nurse their calf and secure enough energy reserve left to migrate back to the feeding ground (Bejder et al., 2019;Christiansen et al., 2016). A low activity level for the calves helps maximize energy allocation into growth (Braithwaite et al., 2015;Ejrnaes & Sprogis, 2021). ...
Understanding the activity budget of mother‐young pairs can inform how energy is allocated and its relation to the development of young. Using suction cup tag data collected off Sainte Marie, Madagascar, during the calving season, we compared the time budgets of mothers and their calves in capital‐breeding humpback whales, investigated the changes with age, and assessed mother‐calf behavioral synchrony based on their swimming speed. We found that mothers and calves allocated much of their time to low‐level activities (i.e., static/quasi‐static or swimming at low speed). Young calves engaged more in slow swimming than older calves and mothers. Mothers with younger calves tended to stay static or quasi‐static less than mothers with older ones. Calves displayed some degree of independence in activities but were also observed synchronizing their activities with their mothers. Depending on the nature of the activity, the initiation of it was driven by either the calf or the mother. Our study provides additional knowledge for understanding the behavioral dynamics and interactions within humpback whale mother‐calf pairs. It provides data that can support the implementation of conservation measures.
... Estimating the morphometric measurements of animals play a crucial role in (Lockyer, 1995(Lockyer, , 1976, evaluating reproduction triggers (Christiansen et al., 2016; 50 Lockyer, 1986) and to categorize animals genders (Danilewicz, 2018;Secchi, 2010). 51 However, obtaining this data in free-ranging animals, in some cases, is challenging, 52 mainly because these animals spend most of their time submerged, and measuring the 53 size and weight of marine mammals makes this work harder, limiting the researchers to 54 obtain this kind of data mainly from the carcass (Danilewicz, 2018;Lockyer, 2007Lockyer, , 1995 1976). ...
I would like to share the preprint of this manuscript entitled: "PhotogrammetryGUI: A Graphical User Interface to Estimate Morphometric Measurements of Marine Megafauna from Scale Calibration Models."
This manuscript presents a graphical interface that allows optimizing the process of extracting morphometric measurements from marine mammals from images collected by drones using the R software.
Additionally, it enables converting the extracted pixel measurements to scalar measurements using scale calibration models!
Here is the link where the file is available:
https://ssrn.com/abstract=4743639
... UAS and SRS offer different advantages and disadvantages for counting wildlife [18,19]. UAS are more suitable for collecting imagery at extremely fine spatial and temporal resolutions; the counts can be more accurate than those conducted in the field by human observers [13] and can be used to estimate animal size or body condition [20,21]. However, studies using UAS often focus on relatively small areas, which can be a limitation for species with large ranges [18,19,22]. ...
Although many medium-to-large terrestrial vertebrates are still counted by ground or aerial surveys, remote-sensing technologies and image analysis have developed rapidly in recent decades, offering improved accuracy and repeatability, lower costs, speed, expanded spatial coverage and increased potential for public involvement. This review provides an introduction for wildlife biologists and managers relatively new to the field on how to implement remote-sensing techniques (satellite and unoccupied aircraft systems) for counting large vertebrates on land, including marine predators that return to land to breed, haul out or roost, to encourage wider application of these technological solutions. We outline the entire process, including the selection of the most appropriate technology, indicative costs, procedures for image acquisition and processing, observer training and annotation, automation, and citizen science campaigns. The review considers both the potential and the challenges associated with different approaches to remote surveys of vertebrates and outlines promising avenues for future research and method development.
... Aerial photogrammetry is currently considered a very useful tool because this technique is noninvasive, and allows working on large numbers of animals over long periods of time, therefore enabling long-term monitoring of populations (Burnett et al., 2019). Aerial photogrammetry has already been shown to be reliable in several cetacean species including blue whales (Balaenoptera musculus, Leslie et al., 2020), gray whales (Eschrichtius robustus, Burnett et al., 2019), humpback whales (Megaptera novaeangliae, Christiansen et al., 2016), southern right whales (Eubalaena australis, Christiansen et al., 2018), sperm whales , killer whales (Orcinus orca, Durban et al., 2015Durban et al., , 2016Fearnbach et al., 2018), short-finned pilot whales (Globicephala macrorhynchus; Noren et al., 2019), or pygmy sperm whales (Currie et al., 2021). Studies are scarcer for species that have smaller body sizes, probably due to the higher difficulty to find and follow animals, but also to their behavior that differs from larger whales (e.g., rapid movements, frequent breaching and arching, and acute reaction to UAV presence, Raoult et al., 2020). ...
... These results were not surprising given the fact that the IPHD populations located in Lingding Bay and Sanniang Bay have been facing a rapid decline in recent years (Huang et al., 2012;Lin et al., 2022). Since body condition is related to survival, health, and reproductive success in mammals (Gaillard et al., 2000), including cetaceans (Christiansen et al., 2014(Christiansen et al., , 2016(Christiansen et al., , 2020Ijsseldijk et al., 2021;Pettis et al., 2004;Sharp et al., 2014). A population composed of dolphins presenting lower body conditions is thus expected to decline faster than a population whose dolphins exhibit higher body conditions. ...
... Due to their ability to reduce person-power requirements and increase the spatial scale of data collection, unmanned aerial vehicles (UAVs) are now widely used in aquatic research for mapping habitats, such as the seabed or waterways, or detecting pollution, such as tracking oil spills (Pajares, 2015). Monitoring aquatic fauna using UAVs is becoming increasingly common; however, this has been mainly limited to visual surveillance of larger marine mammals such as dugongs (Hodgson et al., 2013) and whales (Christiansen et al., 2016;Schoonmaker et al., 2008) or coastal bird communities (Chabot & Bird, 2012). ...
Freshwater ecosystems are endangered, underfunded and understudied, making new methods such as passive acoustic monitoring (PAM) essential for improving the efficiency and effectiveness of data collection. However, many challenges are still to be addressed with PAM: difficulty in accessing research sites, the logistics of implementing large-scale studies and the invasiveness of data collection. When combined with PAM and other sensing strategies, mobile robotics are a promising solution to directly address these challenges. In this paper, we integrate water surface and underwater acoustic monitoring equipment onto a prototype unmanned aerial-aquatic vehicle (UAAV) capable of sailing and flight (SailMAV). Twelve autonomous sailing missions were run on Lake Vrana, Cro-atia, during which acoustic data were collected, and the ability of the UAAV to facilitate the collection of acoustic data demonstrated. Data were simultaneously collected using standard recording methods on buoys and banksides to provide a comparative approach. Acoustic indices were used to analyse the soundscape of underwater acoustic data and BirdNET (a deep artificial neural network) was used on water surface datasets to determine bird species composition. Results show higher species richness and call abundance from UAAV surveys and high site dissimilarity owing to turnover between stationary and UAAV methods. This highlights the success of the UAAV in detecting biodiversity and the com-plementarity of these methods in providing a broad picture of the biodiversity of freshwater ecosystems. Increased bird diversity and underwater acoustic activity in protected areas demonstrate the benefits of protecting freshwater ecosystems; however, site dissimilarity driven by turnover highlights the importance of protecting the entire ecosystem. We show how, by integrating PAM and a UAAV, we can overcome some of the current challenges in freshwater biodiversity monitoring, improving accessibility, increasing spatial scale and coverage, and reducing invasiveness.
... Studying large whale bioenergetics, including energy requirements, is inherently difficult, since their large size makes conventional methods impractical (Moore et al. 2004). Aerial photogrammetry methods using unmanned aerial vehicles (UAVs) offers a novel noninvasive approach to study the size and body condition (relative fat reserves) of large whales (Christiansen et al. 2016(Christiansen et al. , 2018. By measuring the rate of increase in body condition of foraging bowhead whales in Disko Bay over the feeding season, the rate of energy acquisition can be estimated, which in turn can be converted to prey biomass and consumption using the energy content of their prey (Laidre et al. 2007). ...
... The aim of this study was to measure the size and body condition of juvenile and adult bowhead whales in Disko Bay, in order to quantify their energy requirements and prey consumption during the spring feeding season. Since a large proportion of the adult whales that visit Disko Bay are pregnant females ) that require additional energy reserves to support the added cost of reproduction (while in Disko Bay and later on in their reproductive cycle) (Lockyer 1987a;Vikingsson 1995;Christiansen et al. 2016Christiansen et al. , 2021, we hypothesised that (I) adults will increase their body condition over the spring feeding season in Disko Bay. Since lactating females are not observed in Disko Bay, the cost of lategestation would constitute the largest energetic requirement for adult females in the area, followed by energy deposition, maintenance/activity and somatic growth. ...
... SD = 4.2) above the whales. An ideal photograph (or video still frame) represented a whale lying flat at the surface with its dorsal side visible, its body non-arching, and its body contour (both length and width) clearly visible (Christiansen et al. 2016). If the whale rolled over during video recording, we also extracted photographs of the lateral side of the animal (Christiansen et al. 2019). ...
Understanding the energy requirement and prey consumption of Arctic predators is crucial to assess their vulnerability to climate change. The bowhead whale (Balaena mysticetus) is the largest predator of the Arctic, with Disko Bay in Greenland constituting a major feeding ground for a segment (predominantly larger juveniles and adult non-lactating females) of the Eastern Canada-West Greenland population. We used unmanned aerial vehicle photogrammetry to measure the body size and condition of bowhead whales in Disko Bay during the spring (March 26–June 1, 2022), from which we quantified their energy requirements and prey consumption. Measurements of body length, width and height were used to estimate the body volume and condition of juveniles (50 measurements from 39 individuals) and adults (232 measurements from 154 individuals). The body condition of adults increased at a rate of 0.112 percentage points day−1, or 44.1–87.8 L of blubber day−1 (for lengths 13.0–17.0 m). Using published data from harvested whales, the estimated blubber mass gain was 37.1–73.9 kg day−1, which equals an energy deposition rate of 1.01–2.01 GJ day−1. Body maintenance costs were predicted from allometric models, while activity costs and the heat increment of feeding were derived from published archival tag data. Reported length-at-age curves were used to estimate somatic growth costs. The energy requirements for juveniles and adults were 0.621–0.778 GJ day−1 (for lengths 11.0–12.9 m) and 3.662–7.826 GJ day−1 (for lengths 13.0–17.0 m), respectively, which equals a prey consumption rate of 17–22 kg of prey day−1 (0.1% of body mass) and 102–218 kg day−1 (0.3% of body mass).
... The most widely used biometric is total body length. Drone-based photogrammetric studies have assessed the body length of killer whales (Orcinus orca) [119], sperm whales (Physeter macrocephalus) [91], and several species from the family Balaenopteridae [24,25,84,[116][117][118]140], as well as other parameters such as the dorsal surface area [26,44,81,112] or total body volume [72,82,[85][86][87][88]90,96], which have been used to estimate the body condition. Photogrammetric studies assessing body volume and body condition have been widely applied for baleen whale species [23,26,27,44,60,72,[81][82][83][85][86][87][88]90,112,141] and medium and large odontocetes [61,62,96,[120][121][122]. ...
... Drone-based photogrammetric studies have assessed the body length of killer whales (Orcinus orca) [119], sperm whales (Physeter macrocephalus) [91], and several species from the family Balaenopteridae [24,25,84,[116][117][118]140], as well as other parameters such as the dorsal surface area [26,44,81,112] or total body volume [72,82,[85][86][87][88]90,96], which have been used to estimate the body condition. Photogrammetric studies assessing body volume and body condition have been widely applied for baleen whale species [23,26,27,44,60,72,[81][82][83][85][86][87][88]90,112,141] and medium and large odontocetes [61,62,96,[120][121][122]. However, they have also been shown to be feasible and reliable for smaller marine mammals such as dolphins [63,126], porpoises [92], and sirenians [64]. ...
... Drone-based photogrammetry approaches also have limitations in relation to associated error rates [96,141]. These error rates are related with flight altitude [63,91,169]; the UAV model [169]; environmental conditions such as glare, wave refraction, and water clarity [64,169]; the body position of the animal (i.e., body arch, edge certainty, body roll, and depth relative to the water surface) [43,44,60,63,91,112]; the position of the animal in the image frame due to lens distortion [23,43]; and human error in the digitization process [43]. ...
Research on the ecology and biology of marine mammal populations is necessary to understand ecosystem dynamics and to support conservation management. Emerging monitoring tools and instruments offer the opportunity to obtain such information in an affordable and effective way. In recent years, unmanned aerial vehicles (UAVs) have become an important tool in the study of marine mammals. Here, we reviewed 169 research articles using UAVs to study marine mammals, published up until December 2022. The goals of these studies included estimating the number of individuals in populations and groups via photo-identification, determining biometrics and body condition through photogrammetry, collecting blow samples, and studying behavioural patterns. UAVs can be a valuable, non-invasive, and useful tool for a wide range of applications in marine mammal research. However, it is important to consider some limitations of this technology, mainly associated with autonomy, resistance to the marine environment, and data processing time, which could probably be overcome in the near future.
... Photogrammetry is an indirect method for measuring the dimensions of an object from photographs (Burnett et al., 2018;Christiansen et al., 2016aChristiansen et al., , 2019Fearnbach et al., 2011Fearnbach et al., , 2020Groskreutz et al., 2019;Kotik et al., 2023;Krause et al., 2017;Schindler, 2015;Stewart et al., 2021b). When combined with other known photographic variables (e.g., focal length, object-to-lens distance, deviation angles), the pixel distance of two points in Euclidean space can be converted to actual two-dimensional distance (Burnett et al., 2018). ...
... UAVs of various sizes and styles are increasingly used in studies that span the full spectrum of marine mammal science and conservation (Durban et al., 2021;Fiori et al., 2017;Johnston, 2019), including photogrammetric studies on several species of odontocetes and mysticetes (e.g., Christiansen et al., 2016aChristiansen et al., , 2019Durban et al., 2015Durban et al., , 2016Durban et al., , 2021Fearnbach et al., 2011;Groskreutz et al., 2019;Pallin et al., 2022;Zhang et al., 2023). ...
... Most available morphometric data for cetacean species come from whaling data, bycatch, and stranded animals, and our knowledge of body mass and volume of free-ranging species is sparse (Christiansen & Lusseau, 2015;Garrigue et al., 2016;Ichii et al., 1998;Krause et al., 2017;Read, 1990). Direct measurements are extremely invasive, and even lethal, to marine mammals, restricting long-term monitoring (repeated measurement on the same individual or population over time; Christiansen et al., 2016aChristiansen et al., , 2019. Therefore, a noninvasive, accurate, and convenient approach is desirable for conservation efforts. ...
Image processing using traditional photogrammetric methods is a labor‐intensive process. The collection of photogrammetry images during aerial surveys is expanding rapidly, creating new challenges to analyze images promptly and efficiently, while reducing human error during processing. Computer vision‐assisted photogrammetry, a field of artificial intelligence (AI), can automate image processing, greatly enhancing the efficiency of photogrammetry. Here, we present a practical and efficient program capable of automatically extracting the fine‐scale photogrammetry of East Asian finless porpoises ( Neophocaena asiaeorientalis sunameri ). Our results indicated that computer vision‐assisted photogrammetry could achieve the same accuracy as traditional photogrammetry, and the results of the comparisons were validated against the direct measurements. Three‐dimensional (3D) models using computer vision‐assisted photogrammetric morphometrics generated trustworthy body volume estimates. We also explored the one image‐based 3D modeling technique, which is less accurate, but still useful when only one image of the animal is available. Although several limitations exist in the current program, improvements could be made to narrow the virtual‐reality gap when more images are available for machine learning and training. We recommend this program for analyzing images of marine mammals possessing a similar morphological contour.
... Four frames of adequate quality were obtained at altitudes of 21 m (n = 2) and 31 m (n = 2). Frames were selected to meet standard criteria for photogrammetry, such as clear focus, elongated body at the surface, the tip of the rostrum, caudal notch, and the body contour visible, and no body-arching and the whale centered in the field of view of the camera (Christiansen et al., 2016;Durban et al., 2016;de Oliveira et al., 2023), these steps were adopted to avoid possible inaccuracies during the analysis, such as lens distortion or body curvature, which could overestimate or underestimate the collected measurements. ...
... Several aerial photogrammetry protocols based on scale objects proved efficient in estimating measurements in marine mammals (Christiansen et al., 2016;Burnett et al., 2019;Gray et al., 2019;de Oliveira et al, 2023). Even when it is not possible to use a precision sensor to access the flight altitude, these methods provide a simple way to measure marine mammals considering the correlation of the actual object length by their pixel length, assuming a calibration model to fit the measures (Durban et al., 2016;Burnett et al., 2019). ...
... Four frames of adequate quality were obtained at altitudes of 21 m (n = 2) and 31 m (n = 2). Frames were selected to meet standard criteria for photogrammetry, such as clear focus, elongated body at the surface, the tip of the rostrum, caudal notch, and the body contour visible, and no body-arching and the whale centered in the field of view of the camera (Christiansen et al., 2016;Durban et al., 2016;de Oliveira et al., 2023), these steps were adopted to avoid possible inaccuracies during the analysis, such as lens distortion or body curvature, which could overestimate or underestimate the collected measurements. ...
... Several aerial photogrammetry protocols based on scale objects proved efficient in estimating measurements in marine mammals (Christiansen et al., 2016;Burnett et al., 2019;Gray et al., 2019;de Oliveira et al, 2023). Even when it is not possible to use a precision sensor to access the flight altitude, these methods provide a simple way to measure marine mammals considering the correlation of the actual object length by their pixel length, assuming a calibration model to fit the measures (Durban et al., 2016;Burnett et al., 2019). ...
This work presents insights about the biological aspects of a solitary Bryde's whale individual (11.51 meters long), sighted on the northern coast of São Paulo, Brazil.
The data collection was done through drone monitoring, which allowed us to monitor respiratory cycles (ten intervals), speed of movement, behavior, and extract morphometric measurements using aerial photogrammetry techniques.
Through the analysis of the collected data, we aim to gain a better understanding of the ecology and population dynamics of these cetaceans. This information can contribute to conservation efforts and help in the development of appropriate management strategies for their protection.
The application of aerial photogrammetry techniques allows us to obtain accurate measurements of the whales' size and body proportions, providing valuable insights into their physical characteristics and potential adaptations to their environment.
