Bottlenose Dolphins and Antillean Manatees Respond to Small Multi-Rotor Unmanned Aerial Systems

Abstract

Unmanned aerial systems (UASs) 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 toward 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 to 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.

Challenges of collecting blow from small cetaceans

“…Nonetheless, research efforts should be mindful of minimizing the disturbance on dolphins in any attempts to obtain samples (Hodgson and Koh , Ramos et al. ).…”

Use of Drones in Fishery Science

“…), with no or limited disturbance (but see Ramos et al. ). However, the count data collected through UAS surveys only provide information about how many, when, and where surface‐associated wild animals are spotted; these data offer limited to no information about how the organisms react to biotic (e.g., predators, human disturbances, or fisheries activities) or abiotic factors at different temporal and spatial scales.…”

“…Recent technological advancements have allowed researchers to expand the range of questions being addressed using UASs-in particular, the development of novel image processing techniques that not only improve the quality of the data but can also be done in a timely manner, allowing for aerial surveys at ever finer scales. Traditionally, aerial surveys using UASs equipped with high-resolution video cameras have been used in studies of marine wildlife to assess their distribution, density, and abundance Kiszka et al 2016;Rieucau et al 2018), with no or limited disturbance (but see Ramos et al 2018). However, the count data collected through UAS surveys only provide information about how many, when, and where surface-associated wild animals are spotted; these data offer limited to no information about how the organisms react to biotic (e.g., predators, human disturbances, or fisheries activities) or abiotic factors at different temporal and spatial scales.…”

“…Marine mammals (specifically cetaceans, sirenians, and pinnipeds) show a broad range of responses to different platforms, approaches, and proximities. Ramos et al (2018) noted that common bottlenose dolphins Tursiops truncatus exhibited mixed responses to UASs at altitudes of 11-30 m, but Antillean manatees Trichechus manatus manatus fled from overhead flights ranging from 6 to 104 m. Common bottlenose dolphin behavioral responses were highly variable and brief, and they typically reverted to the preresponse state or changed activities. Antillean manatees, however, displayed strong disturbance responses, fled from the aircraft, and actively evaded if pursued.…”

Using small drones to photo-identify Antillean manatees: a novel method for monitoring an endangered marine mammal in the Caribbean Sea

“…Manned aerial surveys can cover larger areas and fly longer compared to small drones, but lack the maneuverability of multirotor drones and the potential of drones for extensive sampling in small areas and at low altitudes (Colefax et al 2018). Drones have been successfully used in a broad range of applications including the detection and counting of marine megafauna (Hodgson et al 2017); photogrammetry to assess cetacean body condition (Durban et al 2015, Christiansen et al 2016; collection of exhaled breath condensate from large baleen whales (Domínguez-Sánchez et al 2018), and behavioral studies (Ramos et al 2018, Torres et al 2018. Drone-based photo-ID studies of bow head whales Balaena mysticetus (Koski et al 2015), killer whales Orcinus orca (Durban et al 2015), and seals (Pomeroy et al 2015) have confirmed the efficacy of this method for identifying numerous marine mammals, but its ap plication to sirenians has not been thoroughly examined.…”