1. A system configured to uniquely identify individual subjects from a group of subjects, the system comprising: electronic memory configured to store a plurality of records, wherein each record corresponds to an individual subject and comprises a feature of one or more characteristics of the individual subject; and one or more processors programmed with computer-executable instructions that, when executed by the one or more processors, program the one or more processors to: obtain a digital image of a current subject that captures a current feature of the one or more characteristics of the current subject; for each record of the plurality of records, compare the current feature of the one or more characteristics captured in the digital image and the feature stored in each record; responsive to a determination that the current feature of the one or more characteristics captured in the digital image does not match any of the features of the one or more characteristics stored in the plurality of records, create a second record corresponding to the current subject; and store the second record in the electronic memory such that the plurality of records includes the second record.