Looking Without Landing—Using Remote Piloted Aircraft to Monitor Fur Seal Populations Without Disturbance

Abstract

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.

Remotely piloted aircraft improve precision of capture–mark–resight population estimates of Australian fur seals

“…4. Furthermore, georeferenced spatial data, which can be difficult or near-impossible to obtain in the field for some fauna (Sarda-Palomera et al 2012, McIntosh et al 2018a, may also be collected as part of RPA surveys. A random sampling technique was implemented, and the number of marked vs. unmarked pups for each sample area (n = 100,000) is presented.…”

“…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). A quadcoptertype RPA (DJI Phantom 4 Pro, D a-Ji ang Innovations (DJI), Shenzhen, China) equipped with an in-built 20-megapixel, 84°field-of-view camera was flown by a licensed RPA operator.…”

“…This mosaic was then sliced into a series of smaller sub-images for ease of counting (McIntosh et al 2018a). This mosaic was then sliced into a series of smaller sub-images for ease of counting (McIntosh et al 2018a).…”

Challenges of collecting blow from small cetaceans

“…) and pinnipeds (McIntosh et al. ), acquire photographic images to estimate population size (Colefax et al. , Hodgson et al.…”

“…Remotely piloted aircraft (e.g., drones) are increasingly being used as the platform of choice to monitor wildlife in many different circumstances (Linchant et al 2015, Gonzalez et al 2016 and have enabled the collection of data that were previously difficult if not impossible to collect. In studies of marine mammals, drones have been used with thermal imaging to assess populations (Seymour et al 2017), determine body condition and identify individual whales (Dawson et al 2017, Christiansen et al 2018, count dugongs (Hodgson et al 2013) and pinnipeds (McIntosh et al 2018), acquire photographic images to estimate population size (Colefax et al 2018, Hodgson et al 2018, record behavior (Goebel et al 2015, Fiori et al 2017, Torres et al 2018, and collect blow samples from whales (Pirotta et al 2017, Dom ınguez-S anchez et al 2018. The collection of biological samples is of particular interest, as drones are potentially a noninvasive tool with minimal impact on the animals (Christiansen et al 2016).…”