FIT and Mark-Recapture
To census or monitor individuals in a small population, a comprehensive collection of footprints can be undertaken to ensure that prints are collected from all animals. However, research/study areas are often too large for this to be practicable, and footprints must then be collected by sampling of a subset of the area rather than a comprehensive collection over the whole area. Mark-recapture studies are often used alongside camera-trapping, where the image of the animal acts as a mark.
Footprint identification can also be employed as a recognition technique in mark-recapture studies and as such provides an opportunity to study species with identifiable tracks that are reclusive, nocturnal, or otherwise difficult to observe directly. Footprint identification also offers the considerable advantage of not requiring handling or marking of study subjects and reduces interference with their behaviour and at the same time can provide important information on population distribution and ranging of individuals.
Collection of footprints must of course satisfy the protocols required for the intended mark-recapture study, e.g., partitioning footprint collection effort into discrete time sets that can be interpreted as capture events, duration of study, intensity of sampling relative to data needs. These considerations will depend on the nature of the subject animal and the terrain they inhabit.
The important question of reliability of identification is not unique to footprint identification but is equally relevant to any technique of recognition, e.g., camera traps, but has received most attention in the literature in the context of recognition by genetic techniques. No doubt, the development of mark-recapture theory with an estimated error rate for identification will continue to develop. We have successfully employed mark-recapture in a short-term study of a closed population of white rhino; even with a low rate of error, further studies will help clarify the kind of misidentifications footprint identification is likely to produce and their impact on mark-recapture estimates.