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Why females grey seals are getting photo identifications

14 December 2012 Last updated at 13:13 GMT

Photo ID is being used to keep track of a colony of breeding grey seals in the Outer Hebrides.

The system uses unique markings on females to identify and track them allowing researchers to monitor their population levels.

A senior research scientist at St Andrews' sea mammal research unit, Dr Paddy Pomeroy is involved in the study and explained how the system worked to BBC Radio 5 live Breakfast.