Using photo ID technology is an important way for researchers to track animals over long stretches of time. It is a strategy used with the unique pattern on humpback whale flukes, with the particular dorsal fin notches and shapes of individual great white sharks, and researchers have even come up with a barcode-like system for cataloging and reading the individual stripe patterns on individual zebras. As technology advances, so too do the opportunities researchers have to use images for identifying individuals within a species, and to have the images in an automated system to make recognition fast and easy. However, the "mug shot" strategy being used for grey seals underscores some problems that can arise -- and how technology can overcome these problems.
University of St Andrews reports on the automated system that scientists at the University of St Andrews, Conservation Research Ltd and Durham University are using to identify the unique coat markings on female grey seas to identify them. It allows them to monitor seals and learn important information without having to actually handle the animal, which puts undue stress on the seal."The automated system uses a form of pattern-recognition to match key identifying marks with thousands of images held in a digital catalogue...Female grey seals have unique coat markings that remain the same during their adult years. This allows any seal, whose image has been captured in photographs, to be identified repeatedly throughout her lifetime."
But what happens when an image of a grey seal is taken when their coat is wet versus dry? Or when patches of dry sand obscure markings on a resting seal? What about when a seal is facing a different angle to the camera, or if it is photographed while swimming versus on land?
"We've built a photo-ID system that allows comparison of seal coat patterns and crucially, takes into account some of the complications arising from data of this type which had been overlooked previously." Lex Hiby, of Conservation Research Ltd, said in the University of St Andrews article. The automated system incorporates the "failure to match" factor and so can still provide the researchers with accurate data using years of accumulated images. It also allows images of seals taken at different locations to be analyzed, allowing researchers even more insight into the movement of the seals and tracking them over years.
The ability to accurately identify grey seals is helping researchers understand their population trends. You can listen to a short explanation of the system and its use on BBC.