Satellites, the all-seeing eyes in the sky: counting elephant seals from space.

• Published in: PLoS ONE
• Main Authors: Clive R McMahon, Hamish Howe, John van den Hoff, Rachael Alderman, Henk Brolsma, Mark A Hindell
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library of Science (PLoS) 2014
• Subjects: Medicine; R; Science; Q; Elephant Seals; Macquarie Island; Mirounga leonina
• Online Access: https://doi.org/10.1371/journal.pone.0092613; https://doaj.org/article/2c7c1f3dea98497894a07f6bd53f5880

Regular censuses are fundamental for the management of animal populations but, are logistically challenging for species living in remote regions. The advent of readily accessible, high resolution satellite images of earth mean that it is possible to resolve relatively small (0.6 m) objects, sufficient to discern large animals. To illustrate how these advances can be used to count animals in remote regions, individual elephant seals (Mirounga leonina) were counted using satellite imagery. We used an image taken on 10/10/2011 to count elephant seals (n = 1790 ± 306 (95%CL)) on the isthmus of Macquarie Island, an estimate which overlapped with concurrent ground counts (n = 1991). The number of individuals per harem estimated using the two approaches were highly correlated, with a slope close to one and the estimated intercept also encompassing zero. This proof of concept opens the way for satellites to be used as a standard censusing technique for inaccessible and cryptically coloured species. Quantifying the population trends of higher order predators provides an especially informative and tractable indicator of ecosystem health.