MARGINAL ATTACK RATE, K-VALUES AND DENSITY DEPENDENCE IN THE ANALYSIS OF CONTEMPORANEOUS MORTALITY FACTORS

1. Procedures for calculating the marginal attack rates and associated k-values from observed death rates are presented for contemporaneous predators or parasitoids that either do or do not discriminate against previously parasitized hosts. 2. The relationships among previous methods for quantifying contemporaneous mortalities are discussed. 3. Solutions to the problem of calculating marginal rates taken from human survival analysis are given under the assumption of proportional hazards. These calculations are easily extended to three or more contemporaneous sources of mortality. 4. The conditions under which proportional hazards can be expected are discussed. 5. These methods are compared to that of Varley et al., 1973 for assessment of density dependence among contemporaneous predators.