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... Entre las bondades de esta herramienta se destaca su uso para la obtención de datos más precisos y confiables sobre la distribución, abundancia y densidad de fauna silvestre utilizando imágenes aéreas sobre grandes extensiones de terreno o ambientes de difícil acceso donde la vegetación o las características del mismo dificultan la observación de los animales así como sus nidos o madrigueras. También han demostrado ser útiles para realizar conteos de especies con comportamiento esquivo a la presencia humana o que se agrupan en grandes números para reproducirse lo que dificulta su conteo exacto (Potapov et al. 2013, Vermeulen et al. 2013, Evans et al 2016, Hodgson et al. 2016, Wich et al. 2016, Adame et al. 2017, Albores-Barajas et al. 2018. A esta tecnología se suma el uso de cámaras térmicas que hacen más evidentes a los organismos aumentando de esta forma la capacidad de detección tanto para el ojo humano como para métodos computacionales de detección automática y análisis (Israel 2011,Chrétien et al. 2015, Chabot y Francis 2016, Spaan et al. 2019. ...
... Cabe señalar que tener una idea más precisa del número de organismos que conforman una población permite tomar decisiones mejor informadas en cuestiones de manejo y conservación de fauna. Con el uso de los VANTs se han obtenido resultados más reales ya que se ha demostrado que las estimaciones poblacionales tienen menos error en comparación con los métodos convencionales, mejorando de esta forma las estimaciones poblacionales (Hodgson et al. 2016, 2018, Adame et al. 2017. ...
... Debido a estas cualidades, las imágenes obtenidas con VANTs son de gran utilidad para el monitoreo y vigilancia de la biodiversidad ya que además del seguimiento y observación de flora y fauna permite observar con detalle las actividades realizadas dentro de áreas naturales protegidas como la tala, la caza y la pesca que se realicen de forma ilegal, incluso controlar actividades permitidas como la agricultura, la ganadería y la pesca sustentable. Además se ha observado que el uso de cámaras infrarrojas mejoran la detección humana, especialmente en los momentos más fríos del día, aunque esto se ve limitado significativamente cuando la cobertura de Para el caso del Lobo Marino de California (Zalophus californianus) se ha observado que los conteos realizados con VANTs son más precisos que aquellos realizados de modo tradicional, y con base en modelos aditivos generalizados se encontró que los conteos tradicionales pierden aproximadamente un tercio de los lobos marinos de todas las clases de edad (crías, juveniles, subadultos y adultos) presentes en la colonia (Fig. 1), incluso más en el caso de las crías (Adame 2016, Adame et al. 2017 Con aves, se han realizado censos de Pardela Mexicana (Puffinus opisthomelas), ave marina de hábitos nocturnos que anida en madrigueras y es considerada como "casi amenazada" por el bajo número colonias reproductivas presentes en islas y la introducción de gatos en las mismas. Dado que la presencia humana puede crear disturbios en sus sitios de anidación y destruir sus madrigueras se ha observado que el uso de fotografías aéreas tomadas desde VANTs ( Fig. 2) es una buena opción para estimar el tamaño de la población con un error de detección muy bajo (5,6%), siendo esta una metodología fácil de replicar para otras especies que anidan en madrigueras en hábitats sin cobertura vegetal densa (Alcalá-Santoyo 2018, Albores- Barajas et al. 2018). ...
Chapter
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En la última década la irrupción de los vehículos aéreos no tripulados (VANTs) o drones ha transformado y revolucionado las ciencias ambientales frente a los métodos tradicionales, creando una nueva frontera del conocimiento al mejorar la calidad y la obtención de los datos de campo. Entre las bondades de esta herramienta se destaca su uso para la obtención de datos más precisos y confiables sobre la distribución, abundancia y densidad de fauna silvestre.
... Unfortunately, only part of the available historical counts of California sea lions in the Gulf of California contains information on pups (Supplementary Information Table S1), and there are no life charts specifically estimated for each reproductive colony 20 ; therefore, such traditional estimates were not feasible. Instead, we focused on counts of all age/sex categories (i.e. total counts), as a consistent parameter that can be also used to estimate pinniped abundance 18,19,40 , especially if some perception and availability biases are accounted for 58,59 . For this, we used all counts available in the literature 16,18,19,21,59,60 and new, reported here for the first time. ...
... Instead, we focused on counts of all age/sex categories (i.e. total counts), as a consistent parameter that can be also used to estimate pinniped abundance 18,19,40 , especially if some perception and availability biases are accounted for 58,59 . For this, we used all counts available in the literature 16,18,19,21,59,60 and new, reported here for the first time. ...
... To solve perception bias and to correct categorization errors, 16 drone-based counts were made parallel to the boat-based counts during the 2016 breeding season (Supplementary Information Table S1), taking aerial photographs of all the areas with presence of California sea lions (see detailed protocol in Adame et al. 59 ). The categorization of California sea lions followed established guidelines for identifying each individual as adult male, sub-adult male, adult female, juvenile, pup, or undetermined 16,61,62 . ...
Article
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The population growth of top predators depends largely on environmental conditions suitable for aggregating sufficient and high-quality prey. We reconstructed numerically the size of a resident population of California sea lions in the Gulf of California during 1978–2019 and its relation with multi-decadal sea surface temperature anomalies. This is the first multi-decadal examination of the sea surface temperature of the Gulf of California and of one of its major predators. A three-decade sustained warming explained the population’s trend accounting for 92% of the variance, including a 65% decline between 1991 and 2019. Long-term warming conditions started in the late 80s, followed by the population’s decline from 43,834 animals (range 34,080–58,274) in 1991 to only 15,291 (range 11,861–20,316) in 2019. The models suggested a century-scale optimum sea surface habitat occurring in mildly temperate waters, from 0.18 to 0.39 °C above the 100-year mean. The mechanistic links of this relation are still untested, but apparent diversification of pelagic fish catches suggests a reduction of high quality prey. We propose this population should be considered vulnerable to any disturbance that could add to the negative effects of the current warm sea surface conditions in the Gulf of California.
... All flight plans were developed in DroneDeploy (https://d ronedeploy.com/). Flight altitudes were chosen so as not to disturb the seals (Adame et al. 2017, McIntosh et al. 2018a) while providing sufficient photograph resolution for pup identification (Seal Rocks 40 m, The Skerries 35 m). Three RPA surveys were flown at Seal Rocks (26 December 2017, 28 December 2017, and 29 December 2017) and two were flown at The Skerries (16 January 2018 and 21 January 2018). ...
... A random sampling technique was implemented, and the number of marked vs. unmarked pups for each sample area (n = 100,000) is presented. distinctions using RPA imagery have been demonstrated for other pinniped, seabird, and penguin species (Goebel et al. 2015, Adame et al. 2017, Brisson-Curadeau et al. 2017). This introduces a new era of demographic investigations where metrics such as the ratio of adult females feeding pups vs. adult females feeding juveniles can be assessed over time and visualized graphically along with density and clustering patterns. ...
... Our findings are consistent with previous work that demonstrates clear advantages of using RPAs for wildlife monitoring (Adame et al. 2017, Brisson-Curadeau et al. 2017). Financial and time (effort) costs of monitoring can be reduced, using off-the-shelf RPAs to capture aerial images, and the assistance of citizen scientists to count animals. ...
Article
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Remotely piloted aircraft (RPA or drones) have become a powerful tool for use in spatial and temporal ecology. Major benefits for environmental management, including improved accuracy and precision for population monitoring of fauna, are being realized. We used Australian fur seals (Arctocephalus pusillus) as a model system to assess how counts and capture–mark–resight (CMR) estimates derived from RPA surveys compared with both traditionally used ground counts and CMR abundance estimates at two colonies in southeastern Australia. To manage the large volume of data, we implemented a citizen science portal SealSpotter to screen RPA imagery for animals of the target age classes. Capture–mark–resight estimates and direct counts using RPA imagery provided measurable improvement in monitoring precision when compared with traditional techniques. A key methodological assumption of CMR estimates is that there is uniform mixing of marked animals across the focal area. This was also validated using spatial data derived from images and linear models, a novel capability of the RPA technique. Our findings have the potential to improve wildlife monitoring techniques for fur seals and are broadly transferable to a wide range of other animal taxa where CMR techniques are employed. Furthermore, they add to the growing body of evidence that demonstrates the benefits of RPAs for wildlife monitoring exceed those of traditional techniques.
... Pinnipeds have been usually counted from land-based viewing stations, although aerial photographs have also provided a viable alternative (Moore, Forney & Weller, 2018). Boat surveys around rookeries are also commonly performed (e.g., Arias-del Razo et al., 2016;Adame et al., 2017). However, crewed aerial and vessel platforms can bias observations due to the animals' reactions to them (Würsig et al., 1998;Born Riget, Dietz & Andriashek, 1999;Dawson et al., 2004;Luksenburg & Parsons, 2009;Hashim & Jaaman, 2011). ...
... On the other hand, despite still requiring fieldwork and offering less area coverage than satellites, UAS allow researchers more freedom in terms of survey timing than satellites and permit coverage in regions of perennial overcast weather (e.g., Goebel et al., 2015). Adame et al. (2017) found their UAS survey to be more accurate than a traditional boat-based survey for the study of a California sea lion (Zalophus californianus) rookery. Furthermore, UAS collect multispectral imagery of higher resolution than satellites, at centimeter (Johnston, 2019) and even sub-centimeter spatial resolutions (Raoult et al., 2020), which is especially relevant for smaller marine mammals like mustelids (e.g., sea otters -Enhydra lutris). ...
Article
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Marine mammals are under pressure from multiple threats, such as global climate change, bycatch, and vessel collisions. In this context, more frequent and spatially extensive surveys for abundance and distribution studies are necessary to inform conservation efforts. Marine mammal surveys have been performed visually from land, ships, and aircraft. These methods can be costly, logistically challenging in remote locations, dangerous to researchers, and disturbing to the animals. The growing use of imagery from satellite and unoccupied aerial systems (UAS) can help address some of these challenges, complementing crewed surveys and allowing for more frequent and evenly distributed surveys, especially for remote locations. However, manual counts in satellite and UAS imagery remain time and labor intensive, but the automation of image analyses offers promising solutions. Here, we reviewed the literature for automated methods applied to detect marine mammals in satellite and UAS imagery. The performance of studies is quantitatively compared with metrics that evaluate false positives and false negatives from automated detection against manual counts of animals, which allows for a better assessment of the impact of miscounts in conservation contexts. In general, methods that relied solely on statistical differences in the spectral responses of animals and their surroundings performed worse than studies that used convolutional neural networks (CNN). Despite mixed results, CNN showed promise, and its use and evaluation should continue. Overall, while automation can reduce time and labor, more research is needed to improve the accuracy of automated counts. With the current state of knowledge, it is best to use semi-automated approaches that involve user revision of the output. These approaches currently enable the best tradeoff between time effort and detection accuracy. Based on our analysis, we identified thermal infrared UAS imagery as a future research avenue for marine mammal detection and also recommend the further exploration of object-based image analysis (OBIA). Our analysis also showed that past studies have focused on the automated detection of baleen whales and pinnipeds and that there is a gap in studies looking at toothed whales, polar bears, sirenians, and mustelids.
... The use of small Unmanned Aircraft Systems (sUAS) in wildlife monitoring (Fust & Loos, 2019) and marine animal research (Aniceto et al., 2018;Adame et al., 2017;Douglas et al., 2017;Fiori et al., 2017;Goebel et al., 2010;Krause et al., 2017;Marine Mammal Commission, 2016;Seymour et al., 2017;Schofield et al., 2019;Sorrel et al., 2019) have been studied, along with costbenefits analyses (MMC, 2016;Raoult et al., 2020). Unmanned aircraft allow access to remote and rugged terrain, enable data collection at a lower cost than traditional aerial methods, and permit observation of species wary of human presence. ...
... Previous studies have shown that pinnipeds have a variety of reactions to the presence of sUAS in their immediate vicinity. Pinniped reactions may include; no response, looking in the direction of the aircraft, or fleeing into the water (Adame et al., 2017;Islam et al., 2017;McIntosh et al., 2018;MMC, 2016;Raoult et al., 2020;Smith et al., 2017). The sound pressure level (SPL) generated by the sUAS and the environment's ambient noise have not been uniformly reported during occurrences of pinniped sUAS reaction, but must be considered prior to aircraft employment. ...
... This is especially true for seals and sea lions (hereafter, pinnipeds) that spend much of the year foraging at sea and can only be counted when they haul out on land to rest or reproduce [4,5]. Yet counts from traditional methods such as visual ground surveys consistently underestimate true animal abundance [6][7][8], especially for dense groups of animals in rugged, inaccessible terrain [9]. Ground surveys also disturb resting animals which can exacerbate underestimation. ...
... Despite being limited by weather and the potential to disturb animals if altitude recommendations are not followed [15], drones have been utilized to count various species [12]. Benefits of drone censuses include: more animals are counted, remote locations can be accessed, they are relatively inexpensive, they require less personnel in the field, minimize animal disturbance, and they create a permanent photographic archive [7,16,17]. However, counting animals manually from drone photographs can be a tedious and timeconsuming task. ...
Article
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Repeated counts of animal abundance can reveal changes in local ecosystem health and inform conservation strategies. Unmanned aircraft systems (UAS), also known as drones, are commonly used to photograph animals in remote locations; however, counting animals in images is a laborious task. Crowd-sourcing can reduce the time required to conduct these censuses considerably, but must first be validated against expert counts to measure sources of error. Our objectives were to assess the accuracy and precision of citizen science counts and make recommendations for future citizen science projects. We uploaded drone imagery from Año Nuevo Island (California, USA) to a curated Zooniverse website that instructed citizen scientists to count seals and sea lions. Across 212 days, over 1,500 volunteers counted animals in 90,000 photographs. We quantified the error associated with several descriptive statistics to extract a single citizen science count per photograph from the 15 repeat counts and then compared the resulting citizen science counts to expert counts. Although proportional error was relatively low (9% for sea lions and 5% for seals during the breeding seasons) and improved with repeat sampling, the 12+ volunteers required to reduce error was prohibitively slow, taking on average 6 weeks to estimate animals from a single drone flight covering 25 acres, despite strong public outreach efforts. The single best algorithm was ‘Median without the lowest two values’, demonstrating that citizen scientists tended to under-estimate the number of animals present. Citizen scientists accurately counted adult seals, but accuracy was lower when sea lions were present during the summer and could be confused for seals. We underscore the importance of validation efforts and careful project design for researchers hoping to combine citizen science with imagery from drones, occupied aircraft, and/or remote cameras.
... This is especially true for seals and sea lions (hereafter, pinnipeds) that spend much of the year foraging at sea and can only be counted when they haul out on land to rest or reproduce [4,5]. Yet counts from traditional methods such as visual ground surveys consistently underestimate true animal abundance [6][7][8], especially for dense groups of animals in rugged, inaccessible terrain [9]. Ground surveys also disturb resting animals which can exacerbate underestimation. ...
... Despite being limited by weather and the potential to disturb animals if altitude recommendations are not followed [15], drones have been utilized to count various species [12]. Benefits of drone censuses include: more animals are counted, remote locations can be accessed, they are relatively inexpensive, they require less personnel in the field, minimize animal disturbance, and they create a permanent photographic archive [7,16,17]. However, counting animals manually from drone photographs can be a tedious and timeconsuming task. ...
Preprint
Full-text available
Repeated counts of animal abundance can reveal changes in local ecosystem health and inform conservation strategies. Unmanned aircraft systems (UAS) such as drones are commonly used to photograph animals in remote locations; however, counting animals in images is a laborious task. Crowd-sourcing can reduce the time required to conduct these censuses considerably, but must first be validated against expert counts to measure sources of error. Our objectives were to assess the accuracy and precision of citizen science counts and make recommendations for future citizen science projects. We uploaded drone imagery from Año Nuevo Island (California, USA) to a curated Zooniverse website that instructed citizen scientists to count seals and sea lions. Across 212 days, over 1,500 volunteers counted animals in 90,000 photographs. We quantified the error associated with several descriptive statistics to extract a single citizen science count per photograph from the 15 repeat counts and then compared the resulting citizen science counts to expert counts. Although proportional error was relatively low (9% for sea lions and 5% for seals during the breeding seasons) and improved with repeat sampling, the 12+ volunteers required to reduce error was prohibitively slow, taking on average 6 weeks to estimate animals from a single drone flight covering 25 acres, despite strong public outreach efforts. The single best algorithm was ‘Median without the lowest two values’, demonstrating that citizen scientists tended to under-estimate the number of animals present. Citizen scientists accurately counted adult seals, but accuracy was lower when sea lions were present during the summer and could be confused for seals. We underscore the importance of validation efforts and careful project design for researchers hoping to combine citizen science with drone imagery.
... Thus, the use of UAVs can provide an alternative to map colonies and aggregations of seabirds and seals. It has been shown for different species that counting individuals on very high resolution aerial images generated by UAV can give more accurate results then counting on ground (Hodgson et al., 2016;Hodgson et al., 2018;Adame et al., 2017). There are various studies available that focus on the comparison between ground counting and aerial images by UAV for birds and seals (Walker, 2014;Chabot et al., 2015;Adame et al., 2017;Hodgson et al., 2018). ...
... It has been shown for different species that counting individuals on very high resolution aerial images generated by UAV can give more accurate results then counting on ground (Hodgson et al., 2016;Hodgson et al., 2018;Adame et al., 2017). There are various studies available that focus on the comparison between ground counting and aerial images by UAV for birds and seals (Walker, 2014;Chabot et al., 2015;Adame et al., 2017;Hodgson et al., 2018). In the Antarctic, Goebel et al. (2015) compared counts of Gentoo-and Chinstrap Penguins on ground with counts from UAV-generated images. ...
Article
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In recent years Unmanned Aerial Vehicles (UAVs) became a fast-developing technology with manifold fields of application. In the field of wildlife biology, it offers the opportunity to quantify populations, to map the spatial distribution of species and to observe the behavior of animals with no or low disturbance. Moreover, UAV based mapping allows to obtain data from sites which are hardly or not accessible and to cover much larger areas than by traditional ground based methods. The advantages of UAV based mapping are of particular relevance under the harsh conditions of Antarctic fieldwork. Whether certain species qualify for UAV based monitoring depends on their detectability from the distance and the distinctiveness of their characteristics in comparison to other species, which has not been studied for Antarctic species in detail so far. This study aims to evaluate how and under which conditions, particularly flight height, Antarctic flying seabird and seal species are detectable in aerial imagery. A trial was conducted comparing the detection rate of different observers for several Antarctic species in aerial images of different ground sample distances. Descriptions of individual appearance as well as body size dimensions are delivered for all species. For most of the investigated species, monitoring proves to be possible from practical flight heights, while others are still very hard to detect even in low altitudes. A concluding table is given aiming to provide a guide for future surveys on which flight altitudes to chose and how to identify focal study objects.
... Adame, Pardo, Salvadeo, Beier, & Elorriaga-Verplancken, 2017;, define the methodology to survey elephants(Vermeulen, Lejeune, Lisein, Sawadogo, & Bouche, 2013), and study distribution and density of the Sumatran orangutan(Wich et al., 2016). ...
... and image system on board of the research vessel allows correction of boat-based counts, as well as giving the opportunity to verify the categorization of the target species, especially when studying large groups such as the bottlenose dolphins off the GBI. The images obtained also allow carefully inspection and potentially eliminate errors.Adame et al. (2017) reported that counts and categorization from the UAV show a smaller amount of errors compared to boat-based ones. Their study conducted on California sea lions suggested that boat-based surveys failed more in categorization of animals than UAV-surveys, especially when the number of animals increased. This can clearly underestimate abund ...
Thesis
Bottlenose dolphins (Tursiops truncatus) are widely distributed in temperate and tropical waters. In New Zealand, Bottlenose dolphins are classified as “nationally endangered”, as there are fewer than 1,000 adults. Great Barrier Island, New Zealand has been identified as a potential hotspot for the North Island population of bottlenose dolphins, with dolphins observed year-round, exhibiting evidence of site fidelity. However, it is unclear how many dolphins are using these areas and why. How the animal uses its environment is a critical step in conservation management for this species and behaviour patterns have not been described for this region. Oceanographic features (e.g. currents, fronts and upwelling), other abiotic factors (temperature, bathymetry and topography), prey distributions and human influences (boating, fishing and environmental contaminants) are known to influence behaviour patterns, group size, and group composition in cetaceans. Behavioural observations in cetaceans are, however, challenging to study, that is, most of the animal activities take place below the water surface, out of sight of boat based observers. Vertical take-off and landing (VTOL) unmanned aerial vehicles (UAVs) represent a novel and cost-effective research tool to investigate cetacean behaviour, as conventional aircraft are expensive, limited in the altitude they can fly at and potentially disturb sensitive wildlife. UAVs are an economical, easy to use and operate, safe, portable and a versatile alternative that may cause little disturbance. In addition, the aerial observation from the UAVs allows assessment of cetacean behaviour from an advantageous perspective and can collect high spatial and temporal resolution data, providing the opportunity to gather accurate data about group size, age class and subsurface behaviour. The use of UAVs is rapidly becoming a common practice both for marine mammal researchers and whale-watchers around the world. However, this new research tool has not yet been used to study bottlenose dolphins in New Zealand waters. In the absence of previously undertaken dedicated UAV surveys, the present thesis is dedicated to investigating and determining how effective lightweight low altitude UAVs are in describing behaviour of bottlenose dolphins off Great Barrier Island. In addition, the thesis compares UAVs with traditional boat-based observations in terms of effectiveness, safety and impact on dolphin behaviour. Surveys were conducted between July 2015 and March 2017 at the west coast of Great Barrier Island. Initially, boat-based surveys were conducted to assess the short term behavioural responses of resting bottlenose dolphins to the VTOL UAV flown at 10 m, 25 m and 40 m altitude. The number of reorientation and tail slap events increased significantly between controls and flights when the UAV was flown at 10 m altitude over the animals. In contrast, no significant difference was detected when the aircraft was flown at 25 m and 40 m altitude. A total of 71 UAV operations were performed over 21 independent groups of bottlenose dolphins. Aggregations of between 6 to 66 individuals were observed with a median group size of 41, whereas 23.8% (n = 5) of the groups contained between 51 and 55 individuals. Calves and neonates were present in the majority of the groups (85.7%, n = 18). Dolphins were found to travel more in summer and autumn, and rest more in winter and spring. Results derived from UAVs were compared with boat data and showed that overall, group size from UAV-derived counts was 71.4% (n = 15) higher, and UAV-derived observations detected significantly more travelling and less resting and less foraging than observations by boat. Results indicate that low altitude UAVs can be used for surveys over a short duration and range and represented a non-invasive tool to study dolphin behaviour when flying at and above 25 m altitude. The UAV surveys can minimise bias and deliver data that are more robust. However, the results conservatively suggest that UAV similar to the Splashdrone should not be flown at 10 m over bottlenose dolphins. Future research should further identify the threshold at which disturbance occurs (i.e. between 10 and 25 m) and also identify how this differs during different behavioural states other than resting. Finally, this research provides baseline information on the optimal use of UAV for bottlenose dolphins surveys and behavioural studies. Additionally, this study contributed to the development of guidelines for future operational use of UAVs around cetaceans in New Zealand waters.
... Oftentimes the collection of these data was previously only possible with the use of manned aircraft, close watercraft approaches, and/or invasive sampling methods (e.g., Koski et al., 2009Koski et al., , 2015Christiansen et al., 2016a). Successful uses of UAS in marine mammal research have included aerial surveys for animal detection, abundance estimation of pinnipeds in breeding colonies, photo-identification of whales, and photogrammetric assessments of body condition and population health (e.g., Koski et al., 2009Koski et al., , 2015Christiansen et al., 2016a;Adame et al., 2017;Krause et al., 2017). Fixed-winged UAS are most often used to detect and count animals during high-altitude long-distance surveys over large areas for estimates of population abundances and distributions (e.g., Hodgson et al., 2013;Adame et al., 2017). ...
... Successful uses of UAS in marine mammal research have included aerial surveys for animal detection, abundance estimation of pinnipeds in breeding colonies, photo-identification of whales, and photogrammetric assessments of body condition and population health (e.g., Koski et al., 2009Koski et al., , 2015Christiansen et al., 2016a;Adame et al., 2017;Krause et al., 2017). Fixed-winged UAS are most often used to detect and count animals during high-altitude long-distance surveys over large areas for estimates of population abundances and distributions (e.g., Hodgson et al., 2013;Adame et al., 2017). Conversely, low-altitude flights and stable hovering with multi-rotor aircrafts enable close approaches directly to animals, for example, to collect exhaled breath condensate (blow) for health assessments of large whales (e.g., Acevedo-Whitehouse et al., 2010;Apprill et al., 2017;Pirotta et al., 2018). ...
Article
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Unmanned aerial systems (UAS) are powerful tools for research and monitoring of wildlife. However, the effects of these systems on most marine mammals are largely unknown, preventing the establishment of guidelines that will minimize animal disturbance. In this study, we evaluated the behavioral responses of coastal bottlenose dolphins (Tursiops truncatus) and Antillean manatees (Trichechus manatus manatus) to small multi-rotor UAS flight. From 2015 to 2017, we piloted 211 flights using DJI quadcopters (Phantom II Vision +, 3 Professional and 4) to approach and follow animals over shallow-water habitats in Belize. The quadcopters were equipped with high-resolution cameras to observe dolphins during 138 of these flights, and manatees during 73 flights. Aerial video observations of animal behavior were coded and paired with flight data to determine whether animal activity and/or the UAS’s flight patterns caused behavioral changes in exposed animals. Dolphins responded to UAS flight at altitudes of 11–30 m, and responded primarily when they were alone or in small groups. Single dolphins and one pair responded to the UAS by orienting upward and turning towards the aircraft to observe it, before quickly returning to their pre-response activity. A higher number of manatees responded to the UAS, exhibiting strong disturbance in response to the aircraft from 6–104 m. Manatees changed their behavior by fleeing the area and sometimes this elicited the same response in nearby animals. If pursued post-response, manatees repeatedly responded to overhead flight by evading the aircraft’s path. These findings suggest that the invasiveness of UAS varies across individuals, species, and taxa. We conclude that careful exploratory research is needed to determine the impact of multi-rotor UAS flight on diverse species, and to develop best practices aimed at reducing the disturbance to wildlife that may result from their use.
... Several recent studies have employed Remotely Piloted Aircraft (RPAs / drones) to evaluate pinniped colonies (Adame et al., 2017;McIntosh et al., 2018). These innovative tools have resulted in successful surveys with accurate total counts of animals visible on land. ...
Technical Report
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This project trialled the use of remote cameras to monitor the relative abundance of Australian sea lions (ASLs, Neophoca cinerea) at three Western Australian (WA) breeding colonies. The research was undertaken by the Department of Primary Industries and Regional Development (DPIRD) to assess whether the analysis of camera footage could be used to estimate ASL relative abundance, providing an alternative to the traditional “boots on the ground” approach (hereon in “BoG”) of visiting colonies to count animals. This report outlines the strengths and limitations of this novel approach rather than providing an update on the population status of ASLs. Remote cameras and associated infrastructure were installed at Buller Island, Haul Off Rock and Wickham Island in the second half of 2018, after which camera images were manually interpreted with the intention of capturing data over an 18-month period (i.e., approximately one reproductive cycle). Overall, counts of ASLs were obtained from the analysis of 563 days (~6,700 hours) of camera footage. These data comprised the number of ASLs identified within the field of view (FoV) of each camera which represented relative abundance estimates for each colony. Day to day variations in the relative abundance of ASLs were estimated for Buller Island and Wickham Island, with limited data on ASL abundance collected for Haul Off Rock due to camera outages. The time series analysis applied to the Buller Island data provides the most detailed information within a single reproductive cycle at a WA colony. To ‘value-add’ from the original aims of the study, remote piloted aircraft (RPA) operations were also conducted within the Recherche Archipelago to provide a greater understanding of the potential application of both methods for on-going monitoring. In summary, the diversity and remoteness of ASL colonies in WA means that no single survey method is likely to be appropriate for the monitoring of all colonies. Installing and maintaining remote cameras at 32 known ASL breeding colonies would be cost-prohibitive and logistically impractical. Instead, camera monitoring at strategic ASL colonies would provide a realistic prospect of collecting long-term abundance data for hard-to-reach Western Australian colonies which remains a challenging prospect using BoG surveys. The ability to view live camera footage could assist with the scheduling of BoG surveys so that on-site surveys can be conducted regularly and safely. Such an approach would require more formal research arrangements to be established between the various state agencies responsible for managing wildlife and fisheries. This project has provided an extensive permanent digital library of camera images that can be made available for use in subsequent ecological and fisheries-related studies.
... Similar results were observed during an experiment using UAV for aerial imaging in pinniped colonies, where there was little or no behavioral response (Moreland et al. 2015;Adame et al. 2017). However, pinnipeds tend to present a varied behavioral response with the UAV approaches at different altitudes. ...
Article
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Strandings of marine mammals, seabirds, and marine turtles in coastal areas can provide valuable information on their ecology. However, gathering information by field teams often incur high costs and effort. This study evaluated the effectiveness of an Unmanned Aerial Vehicle (UAV) to detect stranded animals during beach monitoring programs. The study was carried out between 2016 and 2017 evaluating factors related to the UAV (height and camera angle) and the beach (morphology). Data obtained from the UAV was compared with the traditional method of in situ teams. A total of 120 aerial surveys were conducted on four beaches on the coast of Santa Catarina, Brazil. Eighteen carcasses were recorded by both methods, traditional methodology and UAV. However, six other events were only recorded by in situ monitoring (traditional method) and one event recorded only by the UAV. The time interval between the beach monitoring by the two strategies is probably responsible for the differences. Despite obtaining high-quality aerial images and easily identifying strandings, the UAV cannot completely replace the traditional method due mainly to the impossibility to fly in adverse weather conditions such as high winds and rain. On the other hand, UAVs can complement the data collection information, with less consumption of fossil fuels and damage to the coastal environment.
... Hodgson et al., 2018;Jarrett et al., 2020), as well as marine (e.g. Adame et al., 2017;Koski et al., 2015) and terrestrial mammals (Hu et al., 2020;Vermeulen et al., 2013). This has turned out to be an effective method for studying not only larger vertebrates, mainly birds and mammals, but also reptiles (Elsey & Trosclair, 2016), as well as for other ecological studies (Michez et al., 2016;Puttock et al., 2015). ...
Article
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1. The use of a drone to count the flock sizes of 33 species of waterbirds during the breeding and non-breeding periods was investigated. 2. In 96% of 343 cases, drone counting was successful. 18.8% of non-breeding birds and 3.6% of breeding birds exhibited adverse reactions: the former birds were flushed, whereas the latter attempted to attack the drone. 3. The automatic counting of birds was best done with ImageJ/Fiji microbiology software –the average counting rate was 100 birds in 64 s. 4. Machine learning using neural network algorithms proved to be an effective and quick way of counting birds –100 birds in 7 s. However, the preparation of images and machine learning time is time-consuming, so this method is recommended only for large data sets and large bird assemblages. 5. The responsible study of wildlife using a drone should only be carried out by persons experienced in the biology and behavior of the target animals.
... Comparison of ground counts and aerial survey counts can also indicate bias in counts (e.g., Westlake et al., 1997;Lowry, 1999). The use of unmanned aerial vehicles (UAV) can markedly improve the probability of detecting a pup (e.g., Adame et al., 2017;McIntosh et al., 2018; see also "Aerial survey or ship survey?" below). ...
Article
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Motivated by the need to estimate the abundance of marine mammal populations to inform conservation assessments, especially relating to fishery bycatch, this paper provides background on abundance estimation and reviews the various methods available for pinnipeds, cetaceans and sirenians. We first give an “entry-level” introduction to abundance estimation, including fundamental concepts and the importance of recognizing sources of bias and obtaining a measure of precision. Each of the primary methods available to estimate abundance of marine mammals is then described, including data collection and analysis, common challenges in implementation, and the assumptions made, violation of which can lead to bias. The main method for estimating pinniped abundance is extrapolation of counts of animals (pups or all-ages) on land or ice to the whole population. Cetacean and sirenian abundance is primarily estimated from transect surveys conducted from ships, small boats or aircraft. If individuals of a species can be recognized from natural markings, mark-recapture analysis of photo-identification data can be used to estimate the number of animals using the study area. Throughout, we cite example studies that illustrate the methods described. To estimate the abundance of a marine mammal population, key issues include: defining the population to be estimated, considering candidate methods based on strengths and weaknesses in relation to a range of logistical and practical issues, being aware of the resources required to collect and analyze the data, and understanding the assumptions made. We conclude with a discussion of some practical issues, given the various challenges that arise during implementation.
... The photographs covered the entire colony and were taken at an altitude of 25 to 30 metres. It has been shown that drone flyovers at these altitudes, and even lower, do not affect pinniped behaviour (Adame et al. 2017;McIntosh et al. 2018). The photographs were taken vertically, or at an angle in areas with cliffs. ...
Article
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Long‐term studies that monitor changes in the abundance of pinnipeds are particularly relevant given that these long‐lived species are considered to be indicators of the quality of the ecosystems around them. We report a continuous record of the total abundance by sex and age‐classes of the South American sea lion (Otaria flavescens) in Cobquecura, the most important breeding colony in central Chile over a twelve‐year period (2008 to 2020). We also analysed the demographic trends in South American sea lion abundance at this location. A total of 110 and 43 sea/land based and aerial censuses were performed over the studied period, respectively. The number of sea lions on land was highest in the summer months, which corresponds to the breeding season of the species. The abundance ranged from a minimum of 870 to a maximum of 4,531 individuals from sea/land‐based observations, and from 796 to 4,854 from aerial censuses. This variation was mainly influenced by the number of adult females, the most abundant age‐class in the colony. On the contrary, adult and sub‐adult males were least abundant in the population. The highest numbers of pups were registered in February of each year, ranging from 448 in February 2009 to 1,214 in February 2017. During the study period, we estimated a finite growth rate (λ) of 1.031, suggesting an increase in the population size in the colony, especially in the number of pups. Considering Cobquecura is highly susceptible to anthropogenic disturbance, developing effective long‐term protection through adequate management is critical to better conserve the South American sea lion in the most important breeding colony in central Chile.
... Hodgson et al. 2018;Jarrett et al. 2020), as well as marine (e.g. Koski et al. 2015;Adame et al. 2017) and terrestrial mammals (Vermeulen et al. 2013;Hu et al. 2020). This has turned out to be an effective method for studying larger vertebrates, mainly birds and mammals, but also reptiles (Elsey & Trosclair 2016), as well as for other ecological studies (Puttock et al. 2015;Michez et al. 2016). ...
Preprint
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1. The use of a drone to count the flock sizes of 33 species of waterbirds during the breeding and non-breeding periods was investigated. 2. In 96% of 343 cases, drone counting was successful. 18.8% of non-breeding birds and 3.6% of breeding birds exhibited adverse reactions: in the former, the birds were flushed, whereas the latter attempted to attack the drone. 3. The automatic counting birds was best done with the microbiology software-ImageJ / Fiji: the average bird counting rate was 100 birds in 82 seconds. 4. Machine learning using neural network algorithms proved to be an effective and fast way of counting birds-100 birds in 23 seconds. However, as the preparation of images and machine learning time are time-consuming, this method is recommended only for large data sets and large bird assemblages. 5. The responsible study of wildlife using a drone should only be carried out by persons experienced in the biology and behaviour of the animals concerned. Abstract 1. The use of a drone to count the flock sizes of 33 species of waterbirds during the breeding and non-breeding periods was investigated. 2. In 96% of 343 cases, drone counting was successful. 18.8% of non-breeding birds and 3.6% of breeding birds exhibited adverse reactions: in the former, the birds were flushed, whereas the latter attempted to attack the drone. 3. The automatic counting birds was best done with the microbiology software-ImageJ / Fiji: the average bird counting rate was 100 birds in 82 seconds. 4. Machine learning using neural network algorithms proved to be an effective and fast way of counting birds-100 birds in 23 seconds. However, as the preparation of images and machine learning time are time-consuming, this method is recommended only for large data sets and large bird assemblages. 5. The responsible study of wildlife using a drone should only be carried out by persons experienced in the biology and behaviour of the animals concerned.
... In contrast to most gull species, spatial disposition of nesting pairs within the colony is not clustered, so some breeders could also show nesting separated from the colony in isolated pairs, behaving more territorial than colonial gulls [23,25]. Related to the subject of this study, the species has been recorded as confronting drones aggressively during the breeding stage [29] in some cases shooting down some drones in the breeding area as recorded in other species of the genus Larus [18]. ...
Article
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The use of drones has expanded the boundaries of several activities, which is expected to be utilized intensively in the near future. Interactions between urbanity and naturalness have been increasing while urban expansion amplifies the proximity between urban and natural areas. In this scenario, the interactions between drones and fauna could be augmented. Therefore, the aim of this study was to depict and evaluate the responses of the opportunistic and territorial seagull Larus livens to a small-sized drone during the non-breeding stage in urban areas and natural surroundings. The results evidenced that gulls do not react to drone sounds, coloration, or distance between them and the drone take-off spot. Clearly, the take-off vertical movement triggers an agonistic behavior that is more frequent in groups conformed by two adults, evidencing some kind of territorial response against the device, expressed as characteristic mobbing behavior. Thus, adult settled gulls in touristic and non-urbanized areas displayed agonistic behavior more frequently against the drone. Despite the coastal urban area being a free interaction environment, it evidences a low risk between drone management and territorial seabirds.
... Although weather impacts the ability to observe the animals from all platforms, censuses from high clifftops are particularly limited by difficult circumstances such as meteorological conditions or access factors that could result in poor visibility of individuals, counting errors (e.g. caused by animals lying between others or hiding behind rocks) 35 , or even disturbance and dispersion of specimens 36,37 . For these reasons, aerial photographs are preferred for pinniped censuses since they reduce the errors in population abundance estimates 34 . ...
Article
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Abstract We present estimates of the seasonal and spatial occupation by pinnipeds of the Wildlife Refuge of Ilha dos Lobos (WRIL), based on aerial photographic censuses. Twenty aerial photographic censuses were analysed between July 2010 and November 2018. To assess monthly differences in the numbers of pinnipeds in the WRIL we used a Generalized Linear Mixed Model. Spatial analysis was carried out using Kernel density analysis of the pinnipeds on a grid plotted along the WRIL. Subadult male South American sea lions (Otaria flavescens) were the most abundant pinniped in the WRIL. Potential females of this species were also recorded during half of the census. The maximum number of pinnipeds observed in the WRIL was 304 in September 2018, including an unexpected individual southern elephant seal (Mirounga leonina), and a high number of South American fur seal yearlings (Arctocephalus australis). However, there was no statistically significant difference in counts between months. In all months analysed, pinnipeds were most often found concentrated in the northern portion of the island, with the highest abundances reported in September. This study confirms the importance of the WRIL as a haulout site for pinnipeds in Brazil, recommends that land research and recreational activities occur in months when no pinnipeds are present, and encourages a regulated marine mammal-based tourism during winter and spring months.
... This inference regarding the SBCDs coming from outside the GC also held up when their stable isotope ratios were compared to those of a clearly resident top predator from this region; adult female California sea lions from the Los Islotes rookery in La Paz Bay (Adame et al., 2017), which depends strongly on regional resource availability (Porras-Peters et al., 2008). Elorriaga-Verplancken et al. (2018) reported values of 20.7 ± 1.1 (δ 15 N) and −15.4 ± 0.5 (δ 13 C) for female California sea lions from this location. ...
Article
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The short-beaked common dolphin (Delphinus delphis delphis) (SBCD) is an odontocete inhabiting the Gulf of California (GC), Mexico; distributed widely in temperate to tropical waters, it is sometimes observed close to shore or in shallower areas. On 13 February 2018, a mass stranding of 54 SBCDs occurred in La Paz Bay in the southern GC; 21 individuals died, but the rest were released. Skin samples were removed from dead individuals for stable isotope analysis in order to infer their probable geographical provenance. Their mean S.D. were 17.0 ± 0.3‰ (N) and -18.3 ± 0.2 (C), with no significant differences between sexes or length. These isotope ratios do not correspond to the GC. Their low C and N values reflect offshore foraging grounds not under the 15N-enriching effects of the intense denitrification in the GC. Rather, these values were within the range of other piscivorous odontocetes that have been sampled in the GC and classified as outsiders (Pacific Ocean). Mean total length of these stranded SBCDs was similar to that reported for SBCDs off the Pacific coast of Baja California and southern California, but widely smaller than that reported for both eastern tropical Pacific SBCDs and long-beaked common dolphins (Delphinus delphis bairdii) in the northern and southern GC. These differences in isotopic niche and size between SBCDs stranded in La Paz Bay and long-beaked common dolphins from other regions of the GC highlight the need to be able to distinguish between the common dolphins (Delphinus) that inhabit the GC from those that visit the GC from off the Pacific coast of Baja California. Our findings confirm the ecological importance of the southern GC, where resident and visitor marine mammals congregate, leading to events like mass strandings that provide a unique source of information useful for research and conservation.
... Goebel et al. [28] was one of the first researchers to use drones to estimate the size of individual leopard seals (Hydrurga leptonyx) and suggested that aerial photogrammetry can also be used to estimate the mass of the animals. On the other hand, Adame et al. [32] used UAVs to categorize (sex and age) California sea lions (Zalophus californianus) and claimed that traditional, boat-based counts may underestimate abundance and influence categorization uncertainty. Lowry [33] and Hodgson et al. [34] argued that, in contrast to ground count data, data from manned [33] and unmanned [34] aerial images provide a permanent record. ...
Article
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During the 2019 breeding season (October-December), a battery-powered DIJ Inspire 2 drone was used to investigate a breeding southern elephant seal colony located at Patelnia Point (ASPA 128, King George Island, South Shetland Islands, maritime Antarctica). Twelve unmanned aerial vehicle (UAV) missions conducted 50-70 m above ground level (AGL) were completed to monitor the breeding ground with a maximum of 0.348 km 2. The missions were planned in Pix4D Capture software. A drone, with the support of ground cameras and observations, was used to derive population counts, map harems, and track the phenology of the southern elephant seals. Based on data obtained from the UAV missions, orthophotomaps were created in PIX4D Mapper and then analyzed in QGIS. Calculated values of body size parameters such as body length and orthogonal body surface area were used to determine the age and sex of individuals. Analysis of the ranges of the harems on particular days, supported by an analysis of land conditions that generate physical barriers to the movement of animals, allowed zones in which the transformations of groups of harems took place to be determined. The hypothesized hermeticity of the designated zones was supported by statistical tests. The use of drones allows for comprehensive population analyses of the breeding colonies of elephant seals such as censuses of pups and adult individuals, determination of the sex ratio, and spatial analysis of the distribution of breeding formations. In addition, it allows for a more accurate result than ground counting.
... Previous surveys at the colony indicated that SASL are not disturbed by flights at this altitude. Flights at similar or even lower altitudes do not appear to have affected pinniped behavior46,47 . Photographs were vertical when possible, or with some angle in areas dominated by steep cliffs. ...
Article
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Coastal storms have increased in recent decades, affecting many species, including the South American sea lion (Otaria byronia). Reports of stranded sea lion pups are becoming common in Chile, presumably due to the increase in the frequency and intensity of coastal storms. To validate this assumption, a 10-year database was built by coupling wave generation and coastal propagation models to correlate pure wave parameters (significant wave height Hs, peak period Tp, normalized wave power Hs² Tp) and wave parameters including the tidal level (maximum surface elevation η, modified wave power η² Tp) with records of stranded pups in Cobquecura, the largest breeding colony in central Chile. The correlation between the number of pups stranded per day and wave parameters in the first half of January and the last half of February is poor, while they are stronger for the second half of January and the first half of February. The higher number of stranded pups coincide with coastal storms with normalized wave power values exceeding a threshold of 100 m²/s. Conversely, below this threshold there is wide dispersion between the number of strandings and wave parameters. Identifying wave parameter thresholds could be used to predict when newborn pups will be most affected by coastal storms, and thus help institutions to develop remediation techniques for animals at risk.
... In the context of the growing popularity of unmanned aerial vehicles (UAVs or drones) with high resolution digital cameras in the field of marine mammalogy (e.g., Adame, Pardo, Salvadeo, Beier, & Elorriaga-Verplancken, 2017;Apprill et al., 2017;Dawson et al., 2017;Domínguez-Sánchez, Acevedo-Whitehouse, & Gendron, 2018;Hodgson, Peel, & Kelly, 2017), models such as ours, based on simple measurements and on photographs taken at known distances from an animal will allow remote estimation of body mass for different species and age classes. As they become validated, these types of approaches that decrease the impact derived from handling could have important implications for science and conservation, as they could influence how future research with marine mammals is performed, especially for obtaining data that until now could not be procured without intense physical handling or chemical containment. ...
... Drones (Chapman 2014) are increasingly popular tools in the natural sciences and are notably being used for a growing variety of wildlife-related applications, including: monitoring of birds Ratcliffe et al. 2015;Weissensteiner et al. 2015;McEvoy et al. 2016), marine mammals (Hodgson et al. 2013(Hodgson et al. , 2017Koski et al. 2015;Moreland et al. 2015;Adame et al. 2017;Pirotta et al. 2017; Barnas et al. 2018b), large terrestrial mammals (Vermeulen et al. 2013;Guo et al. 2018;Su et al. 2018;Hu et al. 2020), primates (Van Andel et al. 2015;Wich et al. 2016;Bonnin et al. 2018), and reptiles (Elsey and Trosclair 2016;Schofield et al. 2017;Thapa et al. 2018); wildlife habitat assessment and modeling (Chabot et al. 2014;Puttock et al. 2015;Fraser et al. 2016;Marcaccio et al. 2016;Olsoy et al. 2018); and wildlife conflict management (Israel 2011;Mulero-Pázmány et al. 2013, 2014Olivares-Mendez et al. 2015;Michez et al. 2016). The steady progression of drones into the toolkits of wildlife researchers and managers has been documented through a growing number of literature reviews (Anderson and Gaston 2013;Linchant et al. 2015;Christie et al. 2016;Borrelle and Fletcher 2017;Fiori et al. 2017;Mulero-Pázmány et al. 2017;Mustafa et al. 2018;Rees et al. 2018;Johnston 2019) and the publication of methodological synthesis and "best practice" articles (Junda et al. 2015;Hodgson and Koh 2016;Baxter and Hamilton 2018;Brack et al. 2018;Duffy et al. 2018). ...
Article
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Drones are increasingly popular tools for wildlife research, but it is importantthat the use of these tools does not overshadow reporting of methodological detailsrequired for evaluation of study designs. Thediversity in drone platforms, sensors, andapplications necessitates the reporting of specific details for replication, but there is littleguidance available on how to detail drone use in peer-reviewed articles. Here, we presenta standardized protocol to assist researchers in reporting of their drone use in wildliferesearch. The protocol is delivered in six sections: Project Overview; Drone System andOperation Details; Payload, Sensor, and DataCollection; Field Operation Details; DataPost-Processing; and Permits, Regulations, Training, and Logistics. Each section outlinesthe details that should be included, along with justifications for their inclusion. To facilitateease of use, we have provided two example protocols, retroactively produced for publisheddrone-based studies by the authors of this protocol. Our hopes are that the current versionof this protocol should assist with the communication, dissemination, and adoption ofdrone technology for wildlife research and management.
... These recent studies demonstrate the tool's diverse utility for ecological research applications beyond estimating pinniped presence and abundance (e.g. Adame et al., 2017;Hodgson et al., 2013;Johnston et al., 2017;Koski et al., 2009;McIntosh et al., 2018). However, as the accuracy of drone-derived photogrammetry has only been directly tested for one age-sex class of a single species of pinniped (Krause et al., 2017), the technique requires broader validation. ...
Article
Understanding causes of population change is critical for conservation. Quantifying these causes can be difficult, especially for hard to sample animals like marine vertebrates (e.g. pinnipeds). One solution is to investigate spatiotemporal differences in a species' body condition by measuring body size and mass. Collecting traditional morphological measurements is risky and labour intensive, making less invasive and more efficient techniques desirable. Using Australian sea lions (Neophoca cinerea) of known size and mass as a case study, we tested the suitability of using drone-derived photogrammetry to estimate morphological measurements and assess body condition. Drone-derived measurements were precise and without bias. Animal mass was highly correlated with the 2-dimensional and 3-dimensional measurements of simplified area and volume, explaining >77% and >84% (all P < .01) of the variation in mass, depending on the age-sex class. The juvenile class exhibited the strongest associations (both 2D and 3D R² > 0.99). Using each measurement as a proxy for mass, we calculated body condition indices for each class by standardising the variables by animal length. Photogrammetric indices ranked individuals comparably to those generated from ground-collected data (rs = 0.77–1, depending on age-sex class). Our technique provides a workflow for the non-invasive collection of morphometric data to quantify animal condition, which is transferrable to other pinniped species with species-specific calibration. It will also facilitate the efficient collection of morphometric data of vertebrates from remotely sensed imagery.
... As a consequence, multirotor, remotely piloted helicopters are increasingly being used to replace manned aircraft for marine mammal research. Examples include their use for pinniped colony census research (e.g., Adame, Pardo, Salvadeo, Beier, & Elorriaga-Verplancken, 2017;Goebel et al., 2015;Sweeney et al., 2015) and for the measurement of cetaceans through photogrammetry (e.g., Christiansen et al., 2016;Dawson, Bowman, Leunissen, & Sirguey, 2017;Durban, Fearnbach, Barrett-Lennard, Perryman, & LeRoi, 2015;Durban et al., 2016). In addition, their use as a research tool to study cetacean behavior and ecology has been proposed (Nowacek, Christiansen, Bejder, Goldbogen, & Friedlaender, 2016). ...
Presentation
The use of Unmanned Aerial Vehicles (UAVs) is revolutionizing marine mammal research. These include Vertical Take-Off and Landing (VTOL) UAVs, which have been successfully tested for several applications, including cetacean behavioural surveys. This study represents the first empirical assessment of the effects of in-water tourism interactions on cetacean behaviour using UAV methodology. The Kingdom of Tonga is one of the few countries permitting “swim-with-whales” activities. The Vava’u archipelago, in particular, is one of the most important breeding and calving ground for Oceania humpback whales (Megaptera novaeangliae), where the local swim-with-whales industry focuses primarily on mother-calf pairs. Research on swim-with-cetaceans tourism indicates that these kinds of interactions affect cetacean behaviour and can lead to negative effects on the animals involved. Eighty-two VTOL UAV surveys took place in Vava’u during the 2016 and 2017 whale breeding seasons from both dedicated research and swim-with-whales platforms. Whales’ behavioral state was assessed from aerial videos recorded flying at 30 m altitude and the behavioral budgets in presence and absence of swim-with-whales tourism activities were compared. Whale calves’ dive time, respiration and diving rates, and the time spent at the surface without the mother were also recorded. Results indicate that in-water tourism activities significantly altered humpback whale activity budgets in Vava’u. In particular, mother-calf pairs decreased the proportion of time spent nurturing (P<0.001), while time spent travelling increased two-fold (P=0.001). Furthermore, calf’s respiration rate decreased significantly and the proportion of time alone spent at the surface increased more than four-fold (P=0.001). Finally, whale agonistic displays directed towards swimmers were observed. These findings highlight how UAVs can be a valuable tool for the assessment of cetacean behavioral responses to human activities and reinforce the need for a precautionary management of swim-with-whales tourism in Tonga and other countries, where these types of interactions are permitted.
... As a consequence, multirotor, remotely piloted helicopters are increasingly being used to replace manned aircraft for marine mammal research. Examples include their use for pinniped colony census research (e.g., Adame, Pardo, Salvadeo, Beier, & Elorriaga-Verplancken, 2017;Goebel et al., 2015;Sweeney et al., 2015) and for the measurement of cetaceans through photogrammetry (e.g., Christiansen et al., 2016;Dawson, Bowman, Leunissen, & Sirguey, 2017;Durban, Fearnbach, Barrett-Lennard, Perryman, & LeRoi, 2015;Durban et al., 2016). In addition, their use as a research tool to study cetacean behavior and ecology has been proposed (Nowacek, Christiansen, Bejder, Goldbogen, & Friedlaender, 2016). ...
Article
Vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAVs) are becoming invaluable data collection platforms for cetacean research. In particular, multi-rotors can be used to measure whales and investigate their behavior. Moreover, VTOL UAVs are increasingly accessible for recreational and commercial pilots, and close encounters with whales are widely documented. Unfortunately, quantitative assessments of potential disturbance for the targeted animals are not yet published and guidelines for responsible use of UAVs around cetaceans are still under development. We conducted VTOL UAV surveys on humpback whales in Vava'u, Kingdom of Tonga. Interestingly, whale behaviors such as socializing and nurturing were not detected by trained observers on board the research vessel, but were evident from the UAV. Nevertheless, no significant differences were detected in diving and swim parameters between absence and presence of UAV flying at 30 m altitude. These results suggest that VTOL UAVs can be a non-invasive tool to gather morphometric and behavioral data on baleen whales. However, further research is necessary to establish whether applications that require flight altitudes lower than 30 m and targeting different species may elicit behavioral responses.
... Drone technology (also 'UAV' or 'RPAS'; see Chapman, 2014 andChabot, 2018 for justification to use the term drone) is rapidly gaining popularity as an alternative aerial survey platform for conducting fauna surveys in general, but research investment has also been trialling their utility in marine environments (Goebel et al., 2015;Christie et al., 2016;Hodgson et al., 2016;Kiszka et al., 2016). They may offer increased utility over many current ground, boat and air -based methods (Ivosevic et al., 2015;Adame et al., 2017;Raoult et al., 2018), and offer reduced disturbance towards wildlife and habitats from data collection if executed appropriately (Christiansen et al., 2016;Amerson, 2018;Ramos et al., 2018). Drones also have the potential to offer improved data quality and reliability than manned aircraft because of digital capture methods and the ability to sample areas more intensively, but empirical comparisons between manned aircraft and drones are currently few Angliss et al., 2018;Ferguson et al., 2018). ...
Article
An increase in shark bites, declining shark populations, and changing social attitudes, has driven an urgent need for non-destructive shark monitoring. While drones may be a useful tool for marine aerial surveillance, their reliability in detecting fauna along coastal beaches has not been established. We developed a drone-based shark surveillance procedure and tested the reliability of field-based fauna detections and classifications against rigorous post-analysis. Perception error rates were examined across faunal groups and environmental parameters. Over 316 shark surveillance flights were conducted over 12 weeks, out of a possible 360, with adverse weather preventing most flights. There were 386 separate sightings made in post-analysis, including 17 sightings of shark, 125 of dolphin, 192 of ray, 19 of turtle, 15 of baitfish school, and a further 18 sightings of other fauna. When examining error rates of field-based detections, there were large differences found between fauna groups, with sharks, dolphins, and baitfish schools having higher probabilities of detection. Some fauna, such as turtles, were also more difficult to classify following a detection than other groups. The number of individuals in a sighting, was found to have significant but relatively subtle effects, whilst no environmental covariates were found to influence the perception error rate of field-based sightings. We conclude that drones are an effective monitoring tool for large marine fauna off coastal beaches, particularly if the seabed can be distinguished and post-analysis is performed on the drone-collected imagery. Where live field-based detections are relied upon, such as for drone-based shark surveillance, the perception error rate might be reduced by machine-learning software assistance, such as neural network algorithms, or by utilising a dedicated ‘observer’ watching a high-resolution glare-free screen.
... There is great potential for using remote piloted aircraft (RPAs) to perform surveys as the technology becomes more accessible and cost effective [96][97][98][99][100]. The major benefits of using RPAs is the reduced effort and cost compared to a CMR (for example), reduced disturbance to the seals, provided height limits are tested, and the potential for an increase in the frequency of surveys as a result. ...
Article
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Effective ecosystem-based management requires estimates of abundance and population trends of species of interest. Trend analyses are often limited due to sparse or short-term abundance estimates for populations that can be logistically difficult to monitor over time. Therefore it is critical to assess regularly the quality of the metrics in long-term monitoring programs. For a monitoring program to provide meaningful data and remain relevant, it needs to incorporate technological improvements and the changing requirements of stakeholders, while maintaining the integrity of the data. In this paper we critically examine the monitoring program for the Australian fur seal (AFS) Arctocephalus pusillus doriferus as an example of an ad-hoc monitoring program that was coordinated across multiple stakeholders as a range-wide census of live pups in the Austral summers of 2002, 2007 and 2013. This 5-yearly census, combined with historic counts at individual sites, successfully tracked increasing population trends as signs of population recovery up to 2007. The 2013 census identified the first reduction in AFS pup numbers (14,248 live pups,-4.2% change per annum since 2007), however we have limited information to understand this change. We analyse the trends at breeding colonies and perform a power analysis to critically examine the reliability of those trends. We then assess the gaps in the monitoring program and discuss how we may transition this surveillance style program to an adaptive monitoring program than can evolve over time and achieve its goals. The census results are used for ecosystem-based modelling for fisheries management and emergency response planning. The ultimate goal for this program is to obtain the data we need with minimal cost, effort and impact on the fur seals. In conclusion we identify the importance of power analyses for interpreting trends, the value of regularly assessing long-term monitoring programs and proper design so that adaptive monitoring principles can be applied.
... Recent technological and legislative advances for Remote Piloted Aircraft (RPAs) have provided opportunities to survey seal colonies with greater control and reproducibility than allowed by piloted aerial surveys, as well as better image resolution and (when performed in an optimal fashion) reduced disturbance, logistics and cost (Nilssen et al., 2014;Pomeroy et al., 2015;Hodgson and Koh, 2016;Adame et al., 2017). Such technology may facilitate the collection of more frequent surveys; for example, every year and even several times per breeding season, instead of every 3-5 years (Kirkwood et al., 2010). ...
Article
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Technical advances in monitoring devices, specifically drones, are allowing managers and scientists to obtain quality information on ecosystem health with minimal disturbance to ecosystems and the wildlife they support. Temporal and spatial indicators of ecosystem health, such as population size and/or abundance estimates of marine mammals are the basis for our understanding and prediction of ecosystem change. This is critical for the achievement of conservation goals and sustainable natural resources use. Performing surveys to obtain abundance estimates can be logistically demanding and expensive particularly in offshore marine environments, and can cause significant disturbance to wildlife. These constraints may lead to sub-optimal monitoring programs that reduce the frequency and/or precision of surveys at the cost of data quality and confidence in the resulting analyses. Using Remote Piloted Aircraft (RPA) can be a solution to this challenge. With appropriate testing and ethical consideration; for many situations, RPAs can perform surveys with increased frequency, higher data resolution and less disturbance than typical methods that involve people being present on the ground, thereby enabling more robust programs for monitoring. We demonstrate the process of testing images from RPAs for estimating the abundance of Australian fur seals (Arctocephalus pusillus doriferus) at one of their largest colonies on Seal Rocks, Australia. Two sizes of multirotor (1,400 and 350 mm) with different imaging equipment were tested at 40, 60, and 80 m altitude above sea level. We assessed wildlife disturbance levels and optimized a methodology for effective and economical monitoring of this site. We employed commercially available and open-source software for programming survey flights (Drone Deploy), image processing (Agisoft Photoscan and Autopano Giga), data collation and analyses (R and Python). An online portal "SealSpotter" was developed to facilitate data collection, with the ultimate goal being the engagement of the public as citizen scientists in fur seal counts from RPA images. Preliminary comparisons show that a small RPA at 40 m altitude can produce pup counts 20-32% higher than corresponding ground counts without observable disturbance. The benefits and disadvantages of the RPA trials are discussed, as well as important considerations for those looking to incorporate similar methodologies in their research.
... Recent technological and legislative advances for Remote Piloted Aircraft (RPAs) have provided opportunities to survey seal colonies with greater control and reproducibility than allowed by piloted aerial surveys, as well as better image resolution and (when performed in an optimal fashion) reduced disturbance, logistics and cost (Nilssen et al., 2014;Pomeroy et al., 2015;Hodgson and Koh, 2016;Adame et al., 2017). Such technology may facilitate the collection of more frequent surveys; for example, every year and even several times per breeding season, instead of every 3-5 years (Kirkwood et al., 2010). ...
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Technical advances in monitoring devices, specifically drones, are allowing managers and scientists to obtain quality information on ecosystem health with minimal disturbance to ecosystems and the wildlife they support. Temporal and spatial indicators of ecosystem health, such as population size and/or abundance estimates of marine mammals are the basis for our understanding and prediction of ecosystem change. This is critical for the achievement of conservation goals and sustainable natural resources use. Performing surveys to obtain abundance estimates can be logistically demanding and expensive particularly in offshore marine environments, and can cause significant disturbance to wildlife. These constraints may lead to sub-optimal monitoring programs that reduce the frequency and/or precision of surveys at the cost of data quality and confidence in the resulting analyses. Using Remote Piloted Aircraft (RPA) can be a solution to this challenge. With appropriate testing and ethical consideration; for many situations, RPAs can perform surveys with increased frequency, higher data resolution and less disturbance than typical methods that involve people being present on the ground, thereby enabling more robust programs for monitoring. We demonstrate the process of testing images from RPAs for estimating the abundance of Australian fur seals (Arctocephalus pusillus doriferus) at one of their largest colonies on Seal Rocks, Australia. Two sizes of multirotor (1,400 and 350 mm) with different imaging equipment were tested at 40, 60, and 80 m altitude above sea level. We assessed wildlife disturbance levels and optimized a methodology for effective and economical monitoring of this site. We employed commercially available and open-source software for programming survey flights (Drone Deploy), image processing (Agisoft Photoscan and Autopano Giga), data collation and analyses (R and Python). An online portal “SealSpotter” was developed to facilitate data collection, with the ultimate goal being the engagement of the public as citizen scientists in fur seal counts from RPA images. Preliminary comparisons show that a small RPA at 40 m altitude can produce pup counts 20–32% higher than corresponding ground counts without observable disturbance. The benefits and disadvantages of the RPA trials are discussed, as well as important considerations for those looking to incorporate similar methodologies in their research.
... Manual check Chabot & Bird 2012;Chabot, Craik & Bird 2015;Adame et al. 2017 Count in orthomosaic Chabot, Craik & Bird 2015;Chrétien, Théau & Ménard 2016 Movement Separate strip flights Vermeulen et al. 2013 Simulate movements and flights Hodgson et al. 2017 Telemetry data Terletzky & Koons 2016 Spatially correlated counts ...
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1.Unmanned aerial systems (UAS) are emerging as an accessible and versatile tool for ecologists, promising to revolutionize the way abundance and distribution data are obtained in wildlife studies. Establishment of UAS as an efficient and reliable tool demands understanding how detection errors influence UAS‐derived counts and possible solutions to address them. 2.We describe two types of false negative errors (availability and perception errors) and two types of false positive errors (misidentification and double count) that may bias abundance estimates from UAS surveys. Then, we discuss available methods to address detection errors in UAS surveys and point out challenges for future developments. We present hierarchical models as an integrative framework to account for multiple detection errors and data sets in UAS abundance modeling. 3.Methods to address detection errors in UAS surveys depend on how data are collected (flight plan, images processing and reviewing procedure). Conventional aerial surveys literature offers a set of solutions, especially to deal with false negative errors. Available auxiliary information (such as ground counts and telemetry data) facilitates estimating detection errors, although the versatility of UAS permits exploring novel approaches. Solutions involve planning separated strip transects, temporally replicating flights, carrying out counts in orthomosaics and multiple observer protocol. When automatic image review is used, sub‐sample manual reviewing, trial experiments and semiautomated procedures might deal with algorithm errors. 4.UAS surveys need to be consciously planned, thinking on what kind of errors can significantly affect counts and the use of raw counts and indices should be avoided. Approaches that formally account for false positives are needed, particularly for double counts. Hierarchical modeling (especially N‐mixture models) offers a fruitful framework to explore and combine solutions, integrating multiple data sets and accommodating different detection errors. This article is protected by copyright. All rights reserved.
... The Gulf of California (GC), Mexico, is the habitat for a population of 24,000 to 31,000 California sea lions (Zalophus californianus) (CSL) (Szteren et al., 2006). The southernmost breeding site of the species is located near the mouth of the GC on an islet called Los Islotes, where there is a colony of approximately 500 CSLs (Adame et al., 2017). After the breeding season, a large number of adult male CSLs migrate from California and probably Baja California to more northerly latitudes (Peterson & Bartholomew, 1967;Elorriaga-Verplancken et al., 2013). ...
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A large amount of knowledge has been gathered in relation to male California sea lions’ (Zalophus californianus) migration from colonies in USA to higher latitudes. However there is scarce information of in this regard for colonies in Mexico. We recorded the abundance of subadult males throughout 37 monthly (2012-2016) counts in the southernmost breeding colony (Los Islotes, La Paz Bay in the southern Gulf of California) of the species, and we analyzed stable isotopes (δ15N and δ13C) in fur of stranded subadults in La Paz Bay, and resident females from Los Islotes and the San Benito Archipelago, in the Mexican Pacific (2013-2015). We revealed an update on the subadult males’ seasonality, providing a similar pattern as the one found in 1979-1981, but recording a larger number of individuals, as a result of the population growth of the species over the last four decades. Isotopic results suggested a migratory origin of subadult males sampled in our study area, especially in relation to a larger isotopic niche, because of their wider dispersion relative to resident adult females from Los Islotes and San Benito, and 15N depleted values in subadults (relative to females from Los Islotes) that are typical of the Northeastern Pacific instead of the Gulf of California (15N-eriched baseline). Hence, we hypothesized the entrance of subadult males from the Mexican Pacific into the Gulf of California. These findings are a contribution to what is known about Zalophus californianus in its southernmost distribution margin, especially in terms of males’ dispersion.
... There is great potential for using remote piloted aircraft (RPAs) to perform surveys as the technology becomes more accessible and cost effective [96][97][98][99][100]. The major benefits of using RPAs is the reduced effort and cost compared to a CMR (for example), reduced disturbance to the seals, provided height limits are tested, and the potential for an increase in the frequency of surveys as a result. ...
Conference Paper
Repeated pup censuses for the Australian fur seal (Arctocephalus pusillus doriferus) have been performed across the species’ range every five years since 2002 to monitor population trends. Live pup numbers were estimated at 20 pupping sites using one of the following methods: capture-mark-resight, direct count, or count from aerial photograph. From late December 2013 to February 2014, all known pupping sites for the species were visited. We identified the first overall drop in pup production since seal harvesting ceased in the early 1900s. We also report the first overall drop in pup production since exponential increase commenced in the 1980s, following legislative protection in 1975 that likely curtailed shooting by fishers. The 2013-14 estimate of live Australian fur seal pups (mean ± se = 15,063 ± 83) recorded a 6% per annum drop since 2007-08 (mean ± se = 21,882 ± 187). Previously, pup production had increased at 5% per year between 1986-87 and 2002-03 and 0.3% per year between 2002-03 and 2007-08. Despite identifying a 17-52% drop in pup production at all breeding colonies that had >2,000 pups in 2007-08, we also identified a geographic expansion in breeding range. The species continues to colonise new sites and numbers at recently colonised sites are increasing. Pup production is affected by life history parameters such as adult female survival and fecundity rates, which can be reduced by low prey availability, incidental mortality from fisheries interactions and disease or environmental toxicity. All these factors could have influenced the low pup production in 2013-14.
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In the last decade, drones have become an affordable technology offering highly mobile aerial platforms that can carry a range of sensory equipment into hitherto uncharted areas. Drones have thus become a widely applicable tool for surveying animal populations and habitats in order to assist conservation efforts or to study the behavioral ecology of species by monitoring individual and group behavior. Here, we review current applications for drone surveys and the potential of recently developed computer algorithms for automatic species detection and individual tracking in drone footage. We further review which factors are reportedly associated with animal disturbance during drone presentations and how drones may be used to study anti‐predator behavior. Drone surveys of species and their environments allow scientists to create digital terrain models of habitats, estimate species abundance, monitor individual behavior and study the composition, spatial organization and movement of groups. As drones can influence the behavior of many bird and mammal species directly, they also provide an experimental tool to study animal responses to novel situations, including the drone itself. We conclude that the combined use of drones and automated detection software can assist population estimates and opens new possibilities to study individual and collective behavior. With regard to drone related disturbance and their potential use as predator models we recommend to interpret results against the background of population specific predation pressure and sources of anthropogenic disturbance.
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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.
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The abundance of California sea lions (Zalophus californianus) (CSLs) and Guadalupe fur seals (Arctocephalus philippii townsendi) (GFSs) from the San Benito Archipelago (SBA) was determined through nine monthly surveys in 2014–2015. Assessment of their foraging habits was examined based on the isotopic analysis of pups (maternal indicators) (SIAR/SIBER-R). Environmental variability between 2014 and 2015 was also analyzed, in terms of sea surface temperature (SST) and chlorophyll (Chl-a) concentration. Both otariids reached their highest abundance in July of both years; however, relative to 2014, the 2015 survey showed a 59.7% decline in the total GFS abundance and a 42.9% decrease of GFS pups, while total CSL abundance decreased 52.0% and CSL pup presence decreased in 61.7%. All monthly surveys for both otariids showed a similar trend (>50% decrease in 2015). Compared to 2014, the 2015 GFSs isotopic niche was three times larger (2.0 in 2015, 0.6 in 2014) and the δ13C was significantly lower. CSLs also showed significantly lower δ13C and higher δ15N in 2015. Interannual segregation was greater for CSLs, and their pup body mass was also significantly lower during the 2015 breeding season (mean = 8.7 kg) than in the same season of 2014 (mean = 9.9 kg). The decrease in δ13C for both otariids reflected a more oceanic foraging; most likely associated with the decline in primary productivity in surrounding areas to the SBA, related to a higher SST caused by the 2015 ENSO, with a subsequent increase in foraging effort. These would explain the fewer observed individuals on land, especially pups, which showed diminished body condition (CSLs). This study highlights the importance of marine mammals as sentinel species that respond dynamically to changes in environment, providing valuable information on the effect of ENSO on pinnipeds in Mexican waters.
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The development of advanced technologies to enhance conservation science often outpaces the abilities of wildlife managers to assess and ensure such new tools are safely used in proximity to wild animals. Recently, unmanned aerial systems (UAS) have become more accessible to civilian operators and are quickly being integrated into existing research paradigms to replace manned aircraft. Several federal statutes require scientists to obtain research permits to closely approach protected species of wildlife, such as marine mammals, but the lack of available information on the effects of UAS operations on these species has made it difficult to evaluate and mitigate potential impacts. Here, we present a synthesis of the current state of scientific understanding of the impacts of UAS usage near marine mammals. We also identify key data gaps that are currently limiting the ability of marine resource managers to develop appropriate guidelines, policies, or regulations for safe and responsible operation of UAS near marine mammals. We recommend researchers prioritize collecting, analyzing, and disseminating data on marine mammal responses to UAS when using the devices to better inform the scientific community, regulators, and hobbyists about potential effects and assist with the development of appropriate mitigation measures.
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Since the turn of the century, emerging unmanned aircraft systems (UAS) have found increasingly diverse applications in wildlife science as convenient, very high-resolution remote sensing devices. Achieved or conceptualized applications include optical surveying and observation of animals, autonomous wildlife telemetry tracking, and habitat research and monitoring. As the technology continues to progress and interest from the wildlife science community grows, there may yet be much untapped potential for UAS to contribute to the discipline. We present a review of the published primary literature on the application of UAS in wildlife science and related fields. This is followed by a systematic review of the broader wildlife science literature published since the turn of the century to assess where UAS are likely to make important contributions going forward based on the trends that have emerged thus far. UAS, in particular small lightweight models, are generally well suited for collecting data at an intermediate spatial scale between what is easily coverable on the ground and what is economically coverable with conventional aircraft. They are particularly useful for monitoring wildlife and habitats in places that are difficult to access or navigate from the ground, as well as approaching sensitive or aggressive species.
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The California sea lion (CSL) and the northern elephant seal (NES) are the two most abundant pinniped species inhabiting the San Benito Archipelago (Baja California, Mexico). This study reports the results of the first survey to gather abundance information from continuous breeding seasons (2012-2015) and over the course of a single year (2014). Relative to the previous year, the abundance of CSLs declined in July 2014; however, based on historical censuses, the colony at the archipelago was catalogued as “stable”. Intra-annually, the CSL abundance was regulated by pups and adult females, which reached their peak during the breeding season (July). Moreover, we hypothesize that subadult males from the west coast of Baja California enter the Gulf of California. The NES fluctuations were most affected by the breeding season (February), when the number of pups and adult females peaked, and by the important presence of juveniles in May and September. The NES colony at the archipelago was catalogued as “in decline”, based on previous countings. This high-resolution survey complements past and future studies in the region, and adds another dimension to our understanding of these species, which is largely based on information from their main rookeries in California. © 2015 Universidad Autonoma de Baja California. All rights reserved.
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Regular monitoring of animal populations must be established to ensure wildlife protection, especially when pressure on animals is high. The recent development of drones or unmanned aircraft systems (UASs) opens new opportunities. UASs have several advantages, including providing data at high spatial and temporal resolution, providing systematic, permanent data, having low operational costs and being low-risk for the operators. However, UASs have some constraints, such as short flight endurance.We reviewed studies in which wildlife populations were monitored by using drones, described accomplishments to date and evaluated the range of possibilities UASs offer to provide new perspectives in future research.We focused on four main topics: 1) the available systems and sensors; 2) the types of survey plan and detection possibilities; 3) contributions towards anti-poaching surveillance; and 4) legislation and ethics.We found that small fixed-wing UASs are most commonly used because these aircraft provide a viable compromise between price, logistics and flight endurance. The sensors are typically electro-optic or infrared cameras, but there is the potential to develop and test new sensors.Despite various flight plan possibilities, mostly classical line transects have been employed, and it would be of great interest to test new methods to adapt to the limitations of UASs. Detection of many species is possible, but statistical approaches are unavailable if valid inventories of large mammals are the purpose.Contributions of UASs to anti-poaching surveillance are not yet well documented in the scientific literature, but initial studies indicate that this approach could make important contributions to conservation in the next few years.Finally, we conclude that one of the main factors impeding the use of UASs is legislation. Restrictions in the use of airspace prevent researchers from testing all possibilities, and adaptations to the relevant legislation will be necessary in future.
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Quantifying the distribution and abundance of predators is integral to many ecological studies, but can be difficult in remote settings such as Antarctica. Recent ad-vances in the development of unmanned aerial systems (UAS), particularly vertical takeoff and landing (VTOL) aircraft, have provided a new tool for studying the distri-bution and abundance of predator populations. We detail our experience and testing in selecting a VTOL platform for use in remote, windy, perennially overcast settings, where ac-quiring cloud-free high-resolution satellite images is often impractical. We present results from the first use of VTOLs for estimating abundance, colony area, and density of krill-dependent predators in Antarctica, based upon 65 missions flown in 2010/2011 (n = 28) and 2012/2013 (n = 37). We address concerns over UAS sound affecting wildlife by comparing VTOL-generated noise to ambient and penguin-generated sound. We also report on the utility of VTOLs for missions other than abundance and distribution, namely to estimate size of individual leopard seals. Several character-istics of small, battery-powered VTOLs make them par-ticularly useful in wildlife applications: (1) portability, (2) stability in flight, (3) limited launch area requirements, (4) safety, and (5) limited sound when compared to fixed-wing and internal combustion engine aircraft. We conclude that of the numerous UAS available, electric VTOLs are among the most promising for ecological applications.
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The standard procedure to count birds is a manual one. However a manual bird count is a time consuming and cumbersome process, requiring several people going from nest to nest counting the birds and the clutches. High resolution imagery, generated with a UAS (Unmanned Aircraft System) offer an interesting alternative. Experiences and results of UAS surveys for automatic bird count of the last two years are presented for the bird reserve island Langenwerder. For 2011 1568 birds (± 5%) were detected on the image mosaic, based on multispectral image classification and GIS-based post processing. Based on the experiences of 2011 the results and the accuracy of the automatic bird count 2012 became more efficient. For 2012 1938 birds with an accuracy of approx. ± 3% were counted. Additionally a separation of breeding and non-breeding birds was performed with the assumption, that standing birds cause a visible shade. The final section of the paper is devoted to the analysis of the 3D-point cloud. Thereby the point cloud was used to determine the height of the vegetation and the extend and depth of closed sinks, which are unsuitable for breeding birds.
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Aerial surveys of marine mammals are routinely conducted to assess and monitor species' habitat use and population status. In Australia, dugongs (Dugong dugon) are regularly surveyed and long-term datasets have formed the basis for defining habitat of high conservation value and risk assessments of human impacts. Unmanned aerial vehicles (UAVs) may facilitate more accurate, human-risk free, and cheaper aerial surveys. We undertook the first Australian UAV survey trial in Shark Bay, western Australia. We conducted seven flights of the ScanEagle UAV, mounted with a digital SLR camera payload. During each flight, ten transects covering a 1.3 km(2) area frequently used by dugongs, were flown at 500, 750 and 1000 ft. Image (photograph) capture was controlled via the Ground Control Station and the capture rate was scheduled to achieve a prescribed 10% overlap between images along transect lines. Images were manually reviewed post hoc for animals and scored according to sun glitter, Beaufort Sea state and turbidity. We captured 6243 images, 627 containing dugongs. We also identified whales, dolphins, turtles and a range of other fauna. Of all possible dugong sightings, 95% (CI = 90%, 98%) were subjectively classed as 'certain' (unmistakably dugongs). Neither our dugong sighting rate, nor our ability to identify dugongs with certainty, were affected by UAV altitude. Turbidity was the only environmental variable significantly affecting the dugong sighting rate. Our results suggest that UAV systems may not be limited by sea state conditions in the same manner as sightings from manned surveys. The overlap between images proved valuable for detecting animals that were masked by sun glitter in the corners of images, and identifying animals initially captured at awkward body angles. This initial trial of a basic camera system has successfully demonstrated that the ScanEagle UAV has great potential as a tool for marine mammal aerial surveys.
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California sea lions breed along the Pacific Coast of the United States, south to Baja California, Mexico, and throughout the Gulf of California. Although the population in the United States has been increasing over the last 15 years, the status in the Gulf of California is unknown. The last published census in 1994 yielded an estimate of 31,393 animals, but some rookeries have subsequently declined in abundance. The aim of this study is to provide a new estimate of population size for Califor- nia sea lions in the Gulf of California and to examine the relative risk of extinction among thirteen sites using census data from 1970-2004. Our initial population estimate for 2004 is 17,484 including 4,299 pups, and the total number of sea lions when correction factors were applied was between 24,062 and 31,159. Four of the thirteen rookeries exhibited increasing trends: the two northernmost (Consag and San Jorge), the southernmost (Los Islotes), and San Esteban in the central gulf. The re- maining rookeries were either stable or declining in abundance. During our analysis of total population and pup production trends, we identi- fied a group of sea lion rookeries that are growing in total numbers and pup production, and exhibit low probability of extinction. Another group shows total abundances decreasing, pup production declining, negative population growth, and a high probability of extinction. Finally, a third group of rookeries exhibit high fluctuations in abundance and no clear
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Thesis
Influencia del turismo sobre la conducta del lobo marino de California Zalophus californianus en la lobera Los Islotes, B.C.S., México.
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Summary. Recent work by Reiss and Ogden provides a theoretical basis for sometimes preferring restricted maximum likelihood (REML) to generalized cross-validation (GCV) for smoothing parameter selection in semiparametric regression. However, existing REML or marginal likelihood (ML) based methods for semiparametric generalized linear models (GLMs) use iterative REML or ML estimation of the smoothing parameters of working linear approximations to the GLM. Such indirect schemes need not converge and fail to do so in a non-negligible proportion of practical analyses. By contrast, very reliable prediction error criteria smoothing parameter selection methods are available, based on direct optimization of GCV, or related criteria, for the GLM itself. Since such methods directly optimize properly defined functions of the smoothing parameters, they have much more reliable convergence properties. The paper develops the first such method for REML or ML estimation of smoothing parameters. A Laplace approximation is used to obtain an approximate REML or ML for any GLM, which is suitable for efficient direct optimization. This REML or ML criterion requires that Newton–Raphson iteration, rather than Fisher scoring, be used for GLM fitting, and a computationally stable approach to this is proposed. The REML or ML criterion itself is optimized by a Newton method, with the derivatives required obtained by a mixture of implicit differentiation and direct methods. The method will cope with numerical rank deficiency in the fitted model and in fact provides a slight improvement in numerical robustness on the earlier method of Wood for prediction error criteria based smoothness selection. Simulation results suggest that the new REML and ML methods offer some improvement in mean-square error performance relative to GCV or Akaike's information criterion in most cases, without the small number of severe undersmoothing failures to which Akaike's information criterion and GCV are prone. This is achieved at the same computational cost as GCV or Akaike's information criterion. The new approach also eliminates the convergence failures of previous REML- or ML-based approaches for penalized GLMs and usually has lower computational cost than these alternatives. Example applications are presented in adaptive smoothing, scalar on function regression and generalized additive model selection.
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The first edition of this book has established itself as one of the leading references on generalized additive models (GAMs), and the only book on the topic to be introductory in nature with a wealth of practical examples and software implementation. It is self-contained, providing the necessary background in linear models, linear mixed models, and generalized linear models (GLMs), before presenting a balanced treatment of the theory and applications of GAMs and related models. The author bases his approach on a framework of penalized regression splines, and while firmly focused on the practical aspects of GAMs, discussions include fairly full explanations of the theory underlying the methods. Use of R software helps explain the theory and illustrates the practical application of the methodology. Each chapter contains an extensive set of exercises, with solutions in an appendix or in the book’s R data package gamair, to enable use as a course text or for self-study.
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Several years of census at two colonies in the Gulf of California (Los Cantiles, situated in the northern portion and Los Islotes in the south) were used to define the reproductive period of the California sea lion (Zalophus californianus californianus) in this area. The pattern of births (the length of the breeding period and the mean date of birth) is described using two models: a direct model, based on cumulative counts, and an indirect model, which related the photoperiod and the implanting of the blastocyte. The results of both models show that births begin earlier at Los Cantiles and that synchronization among females was less pronounced at Los Islotes. The mean arrival time of females was similar at both colonies, but differences were observed among the males. This suggests the existence of distinct competitive tactics that may be related to geographic position and the size of the colony. When results are compared with those from San Nicolas (California), it is clear that at Los Cantiles, the reproductive period is more prolonged, begins earlier, and that the time between giving birth and copulation for Gulf sea lions (intervals >30 days) is greater than that estimated for California (21 days).
Article
Photographic and visual aerial surveys to determine current pup production of Northwest Atlantic harp seals were conducted off Newfoundland and in the Gulf of St. Lawrence during March 1999-Photographic surveys were conducted on all whelping concentrations between 14 and 24 March, whereas a visual survey was made of the southern Gulf concentrations on 14 March. Pup production was estimated to be 739,100 (SE = 96,300, CV = 13.0%) at the Front, 82,600 (SE = 22,500, CV = 27.2%) in the northern Gulf, and 176,200 (SE = 25,400, CV = 14.4%) in the southern Gulf (Magdalen Island) for a total of 997,900 (SE = 102,100, 10.2%). Changes in aerial survey estimates indicate that pup production has increased since 1994. A new method to correct for the temporal change in the proportion of pups present on the ice was examined by fitting the percentage of pups observed in three age-dependent stages to a Normal distribution. The results were compared to those obtained from a more complex model used previously. The Simple model produced slightly higher, and hence more conservative, estimates of the proportion of births that had occurred before the time of the survey than the Complex model. When using the Simple model fewer assumptions regarding the start date of pupping and the proportion of older pups remaining on the ice were required, the herd had to be followed for a shorter period, and a more convenient means of calculating confidence limits was available.
Article
Various techniques have been used to count northern elephant seals, Mirounga angustirostris, at rooker-ies in the United States and Mexico. Individuals are customarily counted by observers stationed in observation blinds or on walks atop cliff-tops, along the beach, or among the seals (Le Boeuf, 1974; Stewart, 1989; Stewart et aI., 1994; DeMaster et aLl). Some rookeries are counted from skiffs nearshore (Stewart et aI., 1994). Large-format (228-mm) black-and-white or small-format (35-mm) color-transparency aerial pho-tographs also have been used to count northern elephant seals (Bar-tholomew and Boolootian, 1960; Carlisle andAplin, 1966, 1971; Odell, 1971;Antonelis et aI., 1981; Stewart, 1989), In addition, counts from aerial photographs have been combined With information on the phenology of haulout behavior to estimate el-ephant seal abundance when they are not censused at peak haulout periods (Antonelis et aI., 1981; Stewart et al., 1994). In 1985, scientists ofthe National Marine Fisheries Service began to count northern elephant seals from vertical, color-transparency photo-graphs taken with a large-format camera. A 228-mm-format (carto-graphic) camera was used in 1985 and 1986, but an improved system was adopted in 1987 which used a 126-mm-format (military recon-naissance) camera adjusted for low altitude photography. This paper describes equipment and proce-dures used for counting northern elephant seals from photographs taken with these cameras. Counts of northern elephant seals are pre-sented for San Miguel Island (1985-95), San Nicolas Island (1988-95), Santa Rosa Island (1990-95), and Santa Barbara Is-land (1993-95) off the coast of southern California. The method used to obtain these counts was validated by comparing the preci-sion of counts ofnorthern elephant seals made by biologists on the ground with counts made from large-format aerial color-photo-graphs. The counts of pups that were obtained from photographs taken at each island were then used to estimate the number ofbirths for each year. These birth estimates were then compared with published estimates where other techniques were used in order to evaluate the results obtained by each technique.
Article
Counts of California sea lions (Zalophus californianus) were obtained during the end of the breeding season in western Baja California, Mexico and in the U.S. Eight surveys were conducted at islands in western Baja California during 1989-2000; nine surveys were conducted at four of the Channel Islands in the Southern California Bight (SCB) during 1992-2000; and three surveys were conducted along the coastline and islands in central and northern California during 1998-2000. Sea lions were counted by biologists on the ground or in small vessels and from 126-mm-format aerial color photographs. During the 2000 census, 32,279 sea lions (13,611 pups) were counted at ten rookeries in western Baja California, 120,757 (49,335 pups) were counted at four rookeries in the SCB, and 17,546 (10 pups) were counted in central and northern California. Counts of pups since 1975 and of all age/sex classes since 1927 (obtained from the literature and from these surveys) were used to estimate average annual growth rates and population abundance. Declines in pup production occurred during 1992 in western Baja California (not all years were surveyed) and during 1983, 1992-93, and 1998 in the U.S., all of which corresponded to El NiZo periods. The average annual population growth rate derived from counts of sea lion pups in western Baja California using two methods was estimated to be 0.4% or 3.2% and in the U.S. it was estimated to be 5.8% or 6.1%. In 2000, the western Baja California population was estimated to be 75,000 to 87,000 individuals and the U.S. population was estimated to be 238,000 to 241,000 individuals.
Article
Unmanned aircraft systems (UAS) are remote-controlled devices capable of collecting information from difficult-to-access places while minimizing disturbance. Although UAS are increasingly used in many research disciplines, their application to wildlife research remains to be explored in depth. Here, we report on the use of a small UAS to monitor temporal changes in breeding population size in a Black-headed Gull Chroicocephalus ridibundus colony. This method makes it possible to obtain georeferenced data on nest locations without causing colony disturbance, which would not otherwise be possible via direct ground observations.
Article
Pup production on Sable Island, Nova Scotia, has been increasing exponentially since the early 1960s and by 1997 Sable Island was the largest gray seal colony worldwide. Using an aerial photographic survey, as in previous years, we estimated pup production in January 2004 to determine if this exponential rate of increase had continued. A total of 33,268 pups was counted on the color positives. When corrected for the proportion pups missed on the imagery (1.106 for the 12th; 1.527 on the 13th), the proportion of pups that died prior to the survey (0.031), and the proportion of pups born before the survey (east colony 0.966, west colony 0.962), estimated total pup production was 41,500 with SE = 4,381. The 2004 estimate indicates that pup production on Sable Island has continued to increase, but suggests that the rate of increase (r) may have declined (0.070 compared to previous 0.128). Females from the 1998–2000 cohorts were about 16 times less likely to give birth for the first time at age 4 yr and more than twice as likely at age 6 yr compared to those in the mid-late 1980s. The new estimate of pup production and observed changes in age of primiparity provide the first indication of changes in vital rates of this population. However, additional estimates of pup production and vital rates are needed to confirm this conclusion and to investigate the underlying mechanisms.
Article
Estimates of demographic parameters are essential for assessing the status of populations and assigning conservation priority. In light of the difficulties associated with obtaining such estimates, vital rates are rarely available even for well-studied species. We present the first estimates of age-specific birth rates for female California sea lions (Zalophus californianus) >10 yr of age. These rates were estimated from the reproductive histories of five cohorts of animals branded as pups between 1980 and 1984 at Los Islotes colony in the Gulf of California, Mexico. Age-specific birth rates varied among age classes and ranged between 0.06 and 0.80. The highest birth rates were observed for females between 10 and 15 yr of age, with decreased birth rates among older females. The effect of age, year, and resighting effort were explored using logistic regression analysis. Based on Akaike Information Criteria, birth rates were best explained by female age, while year and resighting effort did not have a significant effect. The odds ratio of producing a pup decreased with age but did not change significantly for middle-aged females. Our estimates of age-specific birth rates are consistent with general patterns observed for other large vertebrates.
Article
Estimates of Steller sea lion (Eumetopias jubatus) pup production are valuable for estimating population trend and size. Currently in Alaska, pups are counted by visiting rookeries, driving older animals into the water, then walking through the rookeries and counting the pups, a highly disruptive procedure. At smaller rookeries, with good vantage points, pups are occasionally counted from the periphery of rookeries without disturbing the sea lions. We evaluated counts made from medium-format, color, aerial photographs as an alternative to drive counts and peripheral counts. Neither the peripheral counts nor the aerial photographic counts disturbed animals on the rokeries. There were strong 1:1 linear relationships between photographic counts and drive counts (r2= 0.966, P < 0.001) and between photographic counts and peripheral counts (r2= 0.999, P < 0.001). Precision was similar for all three methods of counting. We suggest that medium-format, color, aerial photographs is appropriate for routine surveys of Steller sea lion pups in Alaska because it is not disruptive to the hauled-out sea lions and provides comparable estimates with similar precision to drive and peripheral counts. Large areas canbe rapidly surveyed during periods of good weather with a minimum of manpower.
Article
Counts of Steller sea lion (Eumetopias jubatus) pups and non-pups (adults and juveniles) from aerial photographs of rookeries at Año Nuevo Island between 1990 and 1993 were significantly higher than those made on the ground. Based on regression of natural logs of photographic counts versus year, the number of pups declined at a rate of −0.099yr while non-pup numbers declined at −0.315/yr. Examination of ground count data for the same period revealed a significant decline in non-pups (−0.139/yr), but no trend was detected in the ground counts of pups. The regression coefficients from photographic and ground counts of non-pups did not differ significantly. Power analyses using the program TRENDS indicated that detectable rates of change in abundance from four annual surveys were much lower for counts of pups than counts of non-pups where sampling precision was based on fits to linear models.
Article
Pups on San Nicolas Island were counted by two methods; counts by observers on the ground were compared to counts from aerial photographs taken with a 126-mm-format camera with image motion compensation. No difference was detected between photographic counts and ground counts (P= 0.367) when ground counters had unobstructed views. However, ground counts were significantly lower when areas with obstructed views were included in the analysis (P < 0.001). For areas with unobstructed viewing conditions, no difference was detected between counts by the two methods for rock substrates (P= 0.140), sand substrates (P= 0.468), or mixed rock-and-sand substrates (P= 0.968). No differences were found among three replicate aerial photographic censuses (P= 0.432), but a significant difference was found between two replicate ground censuses (P= 0.037). Total counts obtained from the aerial photographs were more precise (CV = 0.042) than counts obtained on the ground (CV = 0.078). Less variability in counts was found between photographic counters than for ground counters.
Article
Recent work by Reiss and Ogden provides a theoretical basis for sometimes preferring restricted maximum likelihood (REML) to generalized cross-validation (GCV) for smoothing parameter selection in semiparametric regression. However, existing REML or marginal likelihood (ML) based methods for semiparametric generalized linear models (GLMs) use iterative REML or ML estimation of the smoothing parameters of working linear approximations to the GLM. Such indirect schemes need not converge and fail to do so in a non-negligible proportion of practical analyses. By contrast, very reliable prediction error criteria smoothing parameter selection methods are available, based on direct optimization of GCV, or related criteria, for the GLM itself. Since such methods directly optimize properly defined functions of the smoothing parameters, they have much more reliable convergence properties. The paper develops the first such method for REML or ML estimation of smoothing parameters. A Laplace approximation is used to obtain an approximate REML or ML for any GLM, which is suitable for efficient direct optimization. This REML or ML criterion requires that Newton-Raphson iteration, rather than Fisher scoring, be used for GLM fitting, and a computationally stable approach to this is proposed. The REML or ML criterion itself is optimized by a Newton method, with the derivatives required obtained by a mixture of implicit differentiation and direct methods. The method will cope with numerical rank deficiency in the fitted model and in fact provides a slight improvement in numerical robustness on the earlier method of Wood for prediction error criteria based smoothness selection. Simulation results suggest that the new REML and ML methods offer some improvement in mean-square error performance relative to GCV or Akaike's information criterion in most cases, without the small number of severe undersmoothing failures to which Akaike's information criterion and GCV are prone. This is achieved at the same computational cost as GCV or Akaike's information criterion. The new approach also eliminates the convergence failures of previous REML-or ML-based approaches for penalized GLMs and usually has lower computational cost than these alternatives. Example applications are presented in adaptive smoothing, scalar on function regression and generalized additive model selection.
Article
This article describes flexible statistical methods that may be used to identify and characterize nonlinear regression effects. These methods are called "generalized additive models". For example, a commonly used statistical model in medical research is the logistic regression model for binary data. Here we relate the mean of the binary response ¯ = P (y = 1) to the predictors via a linear regression model and the logit link function: log
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