A preliminary assessment of using conservation drones for Sumatran orang-utan (Pongo abelii) distribution and density

Abstract

To conserve biodiversity scientists monitor wildlife populations and their habitats. Current methods have constraints such as the costs of ground or aerial surveys, limited resolution of freely-available satellite images, and expensive high resolution satellite images. Recently researchers started to use unmanned aerial vehicles (aka UAVs or drones) for wildlife and habitat monitoring. Here we tested whether we could detect nests of the critically endangered Sumatran orang-utan on imagery acquired from camera mounted drone to determine distribution and density. Our results show that the distribution of nests compares well between aerial and ground based surveys and that relative density (nest/km) shows a significant correlation between these two survey types. The results also indicate that both methods can be used to detect significant differences in relative density between previously degraded reforested and enriched areas. We conclude that orang-utan nest surveys from drones are a promising survey method to determine distribution and (relative) density of this and perhaps other ape species.

Assessment of Chimpanzee Nest Detectability in Drone-Acquired Images

“…An average of 10% of the nests observed from the ground were detected from the air, with improved nest detection in imagery with higher spatial resolution. Our overall detection rate was lower than that previously reported for chimpanzee nests in Gabon (39.9%) [46] and orangutan nests in Indonesia (17.4%) [45]. This discrepancy is likely due to methodological differences and our systematic approach.…”

“…These methods effectively demonstrated that it was indeed possible to detect chimpanzee nests from drones, although these specific approaches resulted in an increased probability of detecting a nest in the drone images for the first approach and on the ground for the second approach. Wich et al [45] used a buffer of 25 m around nests recorded on the ground to select which nest detected from the air would be included in the analyses, comparing the relative density of nests from the aerial and ground-based surveys. The smaller 15 m buffer used in our study could be associated with our smaller detection rate, i.e., we were more conservative regarding what constituted a match.…”

Drones count wildlife more accurately and precisely than humans

“…These benefits have led many practitioners to label RPA as a powerful tool for wildlife ecology (Chabot & Bird, ; Christie, Gilbert, Brown, Hatfield, & Hanson, ; Jones, Pearlstine, & Percival, ; Linchant, Lisein, Semeki, Lejeune, & Vermeulen, ; Watts et al., ). Consequently, RPA are being used for data collection in an increasingly diverse suite of ecological applications, including transect counts of African elephants Loxodonta africana (Vermeulen, Lejeune, Lisein, Sawadogo, & Bouche, ), monitoring for poaching activities (Mulero‐Pazmany, Stolper, van Essen, Negro, & Sassen, ), detecting reptile and arboreal mammal nests (Evans, Jones, Pang, Saimin, & Goossens, ; Wich, Dellatore, Houghton, Ardi, & Koh, ), and estimating the body condition of cetaceans and pinnipeds (Christiansen, Dujon, Sprogis, Arnould, & Bejder, ; Krause, Hinke, Perryman, Goebel, & LeRoi, ).…”

Drones count wildlife more accurately and precisely than humans

“…These benefits have led many practitioners to label RPA as a powerful tool for wildlife ecology Christie, Gilbert, Brown, Hatfield, & Hanson, 2016;Jones, Pearlstine, & Percival, 2006;Linchant, Lisein, Semeki, Lejeune, & Vermeulen, 2015;Watts et al, 2010). Consequently, RPA are being used for data collection in an increasingly diverse suite of ecological applications, including transect counts of African elephants Loxodonta africana (Vermeulen, Lejeune, Lisein, Sawadogo, & Bouche, 2013), monitoring for poaching activities (Mulero-Pazmany, Stolper, van Essen, Negro, & Sassen, 2014), detecting reptile and arboreal mammal nests (Evans, Jones, Pang, Saimin, & Goossens, 2016;Wich, Dellatore, Houghton, Ardi, & Koh, 2016), and estimating the body condition of cetaceans and pinnipeds (Christiansen, Dujon, Sprogis, Arnould, & Bejder, 2016;Krause, Hinke, Perryman, Goebel, & LeRoi, 2017).…”