Evaluation of survival and cause-specific mortality rates using telemetry data

Methods are presented for estimating survival and cause-specific mortality rates from radiomarked animals. Time is partitioned into intervals during which the daily rates are assumed to be constant. The rates are estimated from the number of transmitter-days, the number of mortalities due to particular causes, and the number of days in the time intervals. Potential biases arising from combining data from several individuals marked at different times within an interval or from combining rates from different intervals are identified. Variances and confidence intervals for the estimators are presented. Hypothesis testing and sample-size considerations are also illustrated. Simulation showed that the influence of errors in date of death was small, but misdiagnosis of fate had serious consequences. A microcomputer program is available for performing the analyses.