title: Satellites, the all-seeing eyes in the sky: counting elephant seals from space.
abstract: 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.
authors.affiliation: Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia.
authors.forename: Clive R
authors.initials: CR
authors.lastname: McMahon
authors.affiliation: Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia.
authors.forename: Hamish
authors.initials: H
authors.lastname: Howe
authors.affiliation: Australian Antarctic Division, Channel Highway, Kingston, Tasmania, Australia.
authors.forename: John
authors.initials: J
authors.lastname: van den Hoff
authors.affiliation: Threatened Species & Marine Section, Department of Primary Industries, Water and the Environment, Hobart, Tasmania, Australia.
authors.forename: Rachael
authors.initials: R
authors.lastname: Alderman
authors.affiliation: Australian Antarctic Division, Channel Highway, Kingston, Tasmania, Australia.
authors.forename: Henk
authors.initials: H
authors.lastname: Brolsma
authors.affiliation: Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, Australia.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Hindell
mesh_terms: D000818:Animals; D001315:Australia; D005260:Female; D005843:Geography; D006801:Humans; D008297:Male; D011156:Population Density; D011157:Population Dynamics; D063809:Satellite Imagery; D046048:Seals, Earless; D062206:Spatial Analysis