J. Zool., Lond. (A) (1985) 207, 191-199
'Fingerprinting' snakes: a digital system applied to a population of Natrix maura
A. HAILEY* AND P. M. C. DAVIES
Department of Zoology, University of Nottingham, NG7 2RD
(Accepted 11 December 1984)
(With 1 plate and 3 figures in the text)
An identification system for individual snakes, Natrix maura, was developed, based on photographs of the pattern on the ventral scales. The patterns appeared to be constant, and contained sufficient information (allowing for non-randomness within the pattern) to render duplication unlikely, even in extremely large populations. After digitization, the patterns were compared for overall similarity by computer, and those which matched were checked visually. Using this system on a third of the scales, only 1% of known recaptures (those in which one of the compared photographs was of poor quality) were missed, and coding was reduced to 2.2 min. This sifting makes recognition by natural marks practicable in very large samples, and is robust enough to absorb considerable error in coding.
Contents
Introduction................................................................191
Identification method.......................................................192
Frequency of marks, information content, and reliability of identification..192
Factors influencing information content.....................................195
Matching the digitized patterns.............................................196
Increasing the efficiency of the system.....................................197
General considerations......................................................198
References..................................................................199