Use of unmanned aerial vehicles (UAVs) for mark-resight nesting population estimation of adult female green sea turtles at Raine Island

Abstract

2Nester abundance is a key measure of the performance of the world's largest green 3 turtle rookery at Raine Island, Australia. Abundance surveys have been undertaken in waters 4 adjacent to Raine Island reef using mark-resight counts by surface observer (SO), underwater 5 video (UWV) and unmanned aerial vehicle (UAV) (since 1984, 2013 and 2016 respectively). 6UAV and UWV may provide more cost-effective and less biased alternatives, but estimates 7 must be comparable with the historical estimates. Here we compare the three methods. 8The relative likelihood of resighting a marked turtle was significantly higher by SO 9 than the other methods, which led to lower mark-resight population estimates than by UAV 10 or UWV. Most (96%) variation in resighting probabilities was associated with survey period, 11 with comparatively little variation between consecutive days of sampling or time of day. This 12 resulted in preliminary correction factors of 1.53 and 1.73 from SO-UWV and SO-UAV, 13 respectively. However, the SO and UWV estimates were the most similar when turtle 14 densities were the lowest, suggesting that correction factors need to take into account turtle 15 density and that more data are required. 16 We hypothesise that the UAV and UWV methods improved detection rates of marked 17 turtles because they allowed subsequent review and frame-by-frame analysis, thus reducing 18 observer search error. UAVs were the most efficient in terms of survey time, personnel 19 commitment and weather tolerance compared to the SO and UWV methods.20This study indicates that using UAVs for in-water mark-resight turtle abundance 21 estimation is an efficient and accurate method that can provide an accurate adjustment for 22 historical abundance estimates. Underwater video may continue to be useful as a backup 23 alternative to UAV surveys. 26

Drone‐based thermal remote sensing provides an effective new tool for monitoring the abundance of roosting fruit bats

“…In addition, we show that semi‐automatic CV and OBIA workflows generate results that are comparable to manual point counts of thermal orthomosaics of colonies, providing an efficient alternative to manually assessing the number of flying‐foxes in thermal orthomosaics. Drones equipped with thermal cameras have previously been recommended as a powerful tool for the remote detection of animals (Burke et al., 2019) and have been used to help determine population sizes of several species (Dunstan et al., 2020; Lhoest et al., 2015; Seymour et al., 2017). Our results add to this field of research, demonstrating that drone‐acquired thermal remote sensing can be used as an effective tool for monitoring colonies of the Vulnerable grey‐headed flying‐fox.…”

An analytical view on Unmanned Aircraft Systems

“…In 1951, after WWII; the development work of vehicles such as TB-4 continued for civilian use and in 1955, the Model 1001 was developed by Beechcraft for the US Navy [9]. The US Air force in 1959 were concerned in case of losing the pilots over a hostile territory and hence the force started to plan the usage of uncrewed force [15]. In 1960, after the Soviet Union shot down a U-2, the planning intensified.…”

Mitigating the effects of climate change on the nests of sea turtles with artificial irrigation

“…During the 1980s, hatching success was high and consistently above 75% (Limpus et al., 2003). Since then, hatching success has decreased to 33% in some years (Dunstan & Robertson, 2017). Thus, this population is in the early stages of a major decline in reproductive adults (Dunstan & Robertson, 2019), corresponding to declines in hatchling production first reported in the 1990s (Limpus et al., 2003).…”

“…Since then, hatching success has decreased to 33% in some years (Dunstan & Robertson, 2017). Thus, this population is in the early stages of a major decline in reproductive adults (Dunstan & Robertson, 2019), corresponding to declines in hatchling production first reported in the 1990s (Limpus et al., 2003). Population PSR and ASR are estimated to be 99% and 87%, respectively (Jensen et al., 2018).…”

“…Population PSR and ASR are estimated to be 99% and 87%, respectively (Jensen et al., 2018). High‐density nesting leads to nest destruction by subsequent nesters or reduced PO 2 and high incubation temperatures (Dunstan et al., 2020a). Traditional methods to combat elevated temperatures, such as shading, are not feasible because of the lack of trees, large area to be covered, and a large seabird colony.…”