Effects of Permanent Trap Response in Capture Probability on Jolly-Seber Capture-Recapture Model Estimates

The Jolly-Seber model (Jolly 1965, Seber 1965) is probably the most important open population model for use in capture-recapture experiments. Because of its importance and wide use, it is desirable to have knowledge of the effects of deviations from underlying model assumptions on resulting parameter estimates. Previous investigations have considered the effects of heterogeneity of capture probability (Carothers 1973, Gilbert 1973), tag loss (Arnason and Mills 1981), temporary emigration (Balser 1981), and age-specific differences in mortality rates (Manly 1970). Trap response refers to the situation in which marking an animal causes a change in its capture or survival probability for some time after its initial capture. Robson (1969), Pollock (1975), and Brownie and Robson (1980) have generalized the JollySeber capture-recapture model to permit temporary (e.g., one or more time periods after initial capture) trap response in survival and capture probability. Although a temporary trap response seems reasonable for survival rate and in some instances for capture probability, a permanent trap response in capture probability seems likely in many situations. In this paper we examine bias in Jolly-Seber estimates of survival rate and population size resulting from permanent trap response in capture probability.