title: Photographic identification of individuals of a free-ranging, small terrestrial vertebrate.
abstract: Recognition of individuals within an animal population is central to a range of estimates about population structure and dynamics. However, traditional methods of distinguishing individuals, by some form of physical marking, often rely on capture and handling which may affect aspects of normal behavior. Photographic identification has been used as a less-invasive alternative, but limitations in both manual and computer-automated recognition of individuals are particularly problematic for smaller taxa (<500 g). In this study, we explored the use of photographic identification for individuals of a free-ranging, small terrestrial reptile using (a) independent observers, and (b) automated matching with the Interactive Individual Identification System (I(3)S Pattern) computer algorithm. We tested the technique on individuals of an Australian skink in the Egernia group, Slater's skink Liopholis slateri, whose natural history and varied scale markings make it a potentially suitable candidate for photo-identification. From 'photographic captures' of skink head profiles, we designed a multi-choice key based on alternate character states and tested the abilities of observers - with or without experience in wildlife survey - to identify individuals using categorized test photos. We also used the I(3)S Pattern algorithm to match the same set of test photos against a database of 30 individuals. Experienced observers identified a significantly higher proportion of photos correctly (74%) than those with no experience (63%) while the I(3)S software correctly matched 67% as the first ranked match and 83% of images in the top five ranks. This study is one of the first to investigate photo identification with a free-ranging small vertebrate. The method demonstrated here has the potential to be applied to the developing field of camera-traps for wildlife survey and thus a wide range of survey and monitoring applications.
authors: School of Biological Sciences Flinders University GPO Box 2100 Adelaide South Australia 5001 Australia; Flora and Fauna Division NT Department of Land Resource Management PO Box 1120 Alice Springs Northern Territory 0871 Australia.
authors: Claire E
authors: 0000-0003-0525-7748
authors: CE
authors: Treilibs
authors: CSIRO Land and Water Flagship PO Box 2111 Alice Springs Northern Territory 0871 Australia.
authors: Chris R
authors: CR
authors: Pavey
authors: South Australian Museum North Terrace Adelaide South Australia 5000 Australia.
authors: Mark N
authors: MN
authors: Hutchinson
authors: School of Biological Sciences Flinders University GPO Box 2100 Adelaide South Australia 5001 Australia.
authors: C Michael
authors: CM
authors: Bull
keywords: Abundance; capture‐recapture; lizard; natural markings; non‐invasive