Assessing the disturbance potential of small unoccupied aircraft systems (UAS) on gray seals (Halichoerus grypus) at breeding colonies in Nova Scotia, Canada

Abstract

The use of small unoccupied aircraft systems (UAS) for ecological studies and wildlife population assessments is increasing. These methods can provide significant benefits in terms of costs and reductions in human risk, but little is known if UAS-based approaches cause disturbance of animals during operations. To address this knowledge gap, we conducted a series of UAS flights at gray seal breeding colonies on Hay and Saddle Islands in Nova Scotia, Canada. Using a small fixed-wing UAS, we assessed both immediate and short-term effects of surveys using sequential image analysis and between-flight seal counts in ten, 50 m2 random quadrats at each colony. Counts of adult gray seals and young-of-the-year animals between first and second flights revealed no changes in abundance in quadrats (matched pair t-test p > 0.69) and slopes approaching 1 for linear regression comparisons (r2 > 0.80). Sequential image analysis revealed no changes in orientation or posture of imaged animals. We also assessed the acoustic properties of the small UAS in relation to low ambient noise conditions using sound equivalent level (Leq) measurements with a calibrated U-MIK 1 and a 1/3 octave band soundscape approach. The results of Leq measurements indicate that small fixed-wing UAS are quiet, with most energy above 160 Hz, and that levels across 1/3 octave bands do not greatly exceed ambient acoustic measurements in a quiet field during operations at standard survey altitudes. As such, this platform is unlikely to acoustically disturb gray seals at breeding colonies during population surveys. The results of the present study indicate that the effects of small fixed-wing UAS on gray seals at breeding colonies are negligible, and that fixed-wing UAS-based approaches should be considered amongst best practices for assessing gray seal colonies.

A convolutional neural network for detecting sea turtles in drone imagery

“…As a result, aerial surveys are commonly used to collect population data for these largely inaccessible species, and in recent years, researchers have turned to unoccupied aircraft systems (UAS, or drones) for these tasks (Johnston, ). Surveying populations using UAS can be less logistically challenging than traditional methods, and can also reduce costs and human risk (Arona, Dale, Heaslip, Hammill, & Johnston, ) without sacrificing data quality (Hodgson et al., ; Johnston et al., ). Such surveys have been successfully undertaken with a number of animals, including dugongs (Hodgson, Kelly, & Peel, ), seals (Johnston et al., ; Seymour, Dale, Hammill, Halpin, & Johnston, ), sea turtles (Sykora‐Bodie, Bezy, Johnston, Newton, & Lohmann, ) and several seabird species (Hodgson, Baylis, Mott, Herrod, & Clarke, ).…”

Drone Up! Quantifying Whale Behavior From a New Perspective Improves Observational Capacity

“…Importantly, the reduced noise level of UAS compared to planes and helicopters greatly minimizes behavioral impact on study species (Christiansen et al, 2016b;Smith et al, 2016). Although the potential of UAS technology to enhance marine megafauna behavioral studies has been recognized (Nowacek et al, 2016;Fiori et al, 2017;Rees et al, 2018), few behavioral studies have been conducted, with the exception of sea turtles (Bevan et al, 2016;Schofield et al, 2017), sharks (Rieucau et al, 2008;Gallagher et al, 2018), and assessments of disturbance response to UAS by marine mammals (Pomeroy et al, 2015;Arona et al, 2018;Domínguez-Sánchez et al, 2018) and seabirds (Rümmler et al, 2016;Weimerskirch et al, 2018). To date, no study has applied UAS to investigate the behavioral ecology of marine mammals.…”

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

“…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). Several studies suggest that UAS result in reduced disturbance to marine mammals when compared with traditional research methods (Acevedo-Whitehouse et al, 2010;Moreland et al, 2015;Arona et al, 2018). Therefore, it is important for researchers to develop effective strategies to safely apply UAS to monitor wildlife species to minimize the risk of negative impacts (Chabot and Bird, 2015;Vas et al, 2015;Smith et al, 2016).…”

“…A wide range of species has been documented to exhibit disturbance behaviors to UAS operations in response to UAS (e.g., seabirds, crocodiles, sea turtles, terrestrial and marine mammals; Rümmler et al, 2016;Brisson-Curadeau et al, 2017;Mulero-Pázmány et al, 2017;Bevan et al, 2018). Among marine mammals, pinnipeds exhibited rapid group dispersal following multi-rotor UAS approaches (Pomeroy et al, 2015;Sweeney et al, 2015), but were largely unaffected by fixed-wing UAS flying at high altitudes (Arona et al, 2018), where aircrafts may be relatively undetectable by most wildlife. Multi-rotor UAS operated at altitudes of 9-200 m did not elicit observable behavioral responses in studies of toothed whales (e.g., sperm whales Physeter macrocephalus: Acevedo-Whitehouse et al, 2010; killer whales Orcinus orca: Durban et al, 2015) and baleen whales (e.g., blue whales Balaena mysticetes; gray whales Eschrichtus robustus: Acevedo-Whitehouse et al, 2010; humpback whales Megaptera novaeangliae: Christiansen et al, 2016a).…”