Precision and bias in estimates of apparent survival ( Φ ) and re-encounter rate ( p ). a) Estimates of Φ and p in relation to sub-sample size. In both parameters the variation of estimates strongly increased inversely to sub-sample size. b) Average estimates of apparent survival in relation to re-encounter probability. Small sub-samples were likely to give biased estimates of the re-encounter rate and in turn, local survival. Dot size and color indicate sample size categories (small light gray n ≤100, medium, gray n = 101 to 300, large, black n >300). The line gives the regression for samples of n <100 individuals. With large sample sizes the estimates converge to a narrow range and the correlation disappears.