Drones Minimize Antarctic Predator Responses Relative to Ground Survey Methods: An Appeal for Context in Policy Advice

Abstract

Unoccupied aerial systems (UAS) have become common tools for ecological monitoring and management. However, UAS use has the potential to negatively affect wildlife. Both policy makers and practitioners require data about the potential impacts of UAS on natural biota, but few studies exist and some of the published results conflict. We conducted two experiments to assess the responses of chinstrap penguins (Pygoscelis antarcticus), Antarctic fur seals (Arctocephalus gazella), and leopard seals (Hydrurga leptonyx) to UAS overflights. First, to provide a baseline for assessing disturbance from UAS operations, we compare behavioral responses from UAS flights to those from traditional, ground surveys. Second, to inform users and policy makers about preferred flight methods, we assess behavioral and physiological responses to UAS flown at specific altitudes, during different stages of breeding chronology, and with other site factors. Between January 2017 and March 2018 we conducted 268 UAS flight approaches and 36 ground-based surveys at Cape Shirreff, Antarctic Peninsula. We applied generalized linear mixed effects models and Kruskal-Wallis tests to 10,164 behavioral scores obtained from three independent observers. When directly compared, behavioral responses by all species to UAS overflights at 30 m were not different from control periods, while responses to ground surveys were significantly more intense. Behavioral responses generally increased as UAS flew lower, and for penguins those increases intensified as the breeding season progressed (i.e., guard and molt stages). We argue that results from UAS wildlife response studies need to be assessed relative to the impacts of alternative methods, and within the ecological context of the target species. Finally, we suggest data-driven best practices for both UAS use and for the design of future UAS-wildlife response studies.

An automated work-flow for pinniped surveys: A new tool for monitoring population dynamics

“…We did not observe any clear disturbance to the seals by the drones at 40 m altitude while collecting orthomosaics or during zoom-photo/video surveys at 100 m altitude. The sizes of the drones used and altitudes of flight have shown to cause low disturbance to marine mammals, such as harbour seals (Duporge et al, 2021;Palomino-González et al, 2021;Krause et al, 2021). Counting pups with telescopes on islands with complex topography requires that observers drive near Skerries by boat and count seals as they escape into the water, which can lead to unnecessary short-term stress both to lactating mothers and pups.…”

“…We performed manually operated flights remotely from islands without haul-out sites to avoid seal disturbance (Krause et al, 2021). The flight altitude was 100 m and the vertical distance to the seals when photographed by this method was between 100 and 150 m. Observations were made using a x30 optical zoom camera (DJI, Zenmuse-Z30) mounted on a quadcopter drone (DJI,.…”

“…Orthomosaic collection can be easily replicated with low-cost drones, by providing high-resolution mosaics (1 cm/pixel) to count pups and older seals as well as documenting their spatial location, which could be important when revisiting colonies. In addition to population surveys, drones with zoom-video cameras can provide new information on seal behaviours, such as mother and pup interactions during lactation, or response to disturbance (Krause et al, 2021). Orthomosaics with the location of each individual older seal and pup can be used to understand how groups are distributed across skerries and islands and the impact of human presence, weather patterns, spread of infectious diseases, etc.…”

A review of leopard seal (Hydrurga leptonyx) births and pups using a standardised age-class classification system

“…Or, if possible, photogrammetry can be used from the ground, or low-disturbance unoccupied aerial systems (UAS e.g. Krause et al 2021) can accurately obtain SL (Krause et al 2017) or photo and video evidence of birth attributes could be gathered. Such data would substantially aid in the classification of leopard seal records when considering the birth/newborn/ pup age classes and together with the use of the SACCS, comparisons can be made between regions, populations and studies.…”

Surveying cliff-nesting seabirds with unoccupied aircraft systems in the Gulf of Alaska

“…For many species, UAS represent a new form of aerial disturbance that can elicit as-yet uncharacterized species-specific responses to different types of exposure (Smith et al 2016). UAS appear to cause less disturbance than conventional aircraft or ground-based surveys for a range of species (Moreland et al 2015;Borrelle and Fletcher 2017;Sweeney et al 2015;Krause et al 2021), but in some cases UAS appear to elicit stress behaviors or physiological responses that may impact breeding success and reduce fitness (Grémillet et al 2012;Ditmer et al 2015;McEvoy et al 2016;Smith et al 2016;Vas et al 2015;Weimerskirch et al 2018;Rush et al 2018). Furthermore, many incidents of wildlife harassment by recreational UAS users have already been documented (Rebolo-Ifrán et al 2019).…”