Estimation of Time-Specific Survival Rates from Tag-Resighting Samples: A Generalization of the Jolly-Seber Model

Abstract

The resighting, rather than recapturing, of individuals that were initially captured, tagged and returned to a population offers a means of circumventing the often traumatic and sometimes fatal effect of repeated capture and handling of wild animals in a tag-recapture study. The behavioral effect of initial capture and tagging, however, must often be accounted for in the model. If sighting records are restricted to tagged individuals, with no attempt made to estimate a tagged/untagged ratio in the population, the model requirements are simplified to include only the modeling of mortality among tagged individuals and to exclude recruitment parameters in the unobserved, untagged portion of the population. Shortterm capture/tagging effects of specified duration (i.e. lasting for only one time-period) are incorporated into the proposed model, and their biasing effects are thereby eliminated from estimates of time-specific survival rates. Standard error formulas and tests of the model are provided in this generalization of the Jolly-Seber method of tag-recapture analysis.