K. Ullas Karanth developed a photographic capture-recapture model approach for estimating tiger populations. A 1995 study used repeated camera trap sampling in Nagarahole, recognizing individual tigers across photographs instead of equating the photograph count with the number of animals.[ref]
The study reported photographic captures of individuals across nine sampling occasions. A model allowing animals to differ in capture probability was appropriate for those data.[ref]
Estimating tiger Panthera tigris populations from camera-trap data using capture-recapture models by K. Ullas Karanth. Abstract: sample counts and individual heterogeneity
The count of ten distinct photographed tigers and an estimate of the underlying population answer different questions. Repeated sightings identify recaptures, while unseen individuals require inference. Variation in how readily animals pass a camera trap matters even when their identities can be recognized accurately.
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