Generation length and percent mature estimates for IUCN assessments of cetaceans

Abstract

We estimated generation length and percent mature for 58 cetacean species to assess theirstatus using criteria developed by the IUCN. We first reviewed the literature and types of dataavailable and then developed a set of simple rules to ensure consistent use of the best availabledata to estimate these parameters. The method we developed estimated percent mature for thecurrent population and the generation length for the pre-disturbance population using a simple 5-parameter demographic model based on age of first reproduction, inter-birth interval, maximumage of reproductive females, calf survival rate, and non-calf survival. When parameter estimateswere not available for a species, we used available estimates from congeners. The maximum ageof females was estimated based on the relationship between maximum length of females andmaximum age of females for all species with data available. Generation length and percentmature were not calculated if data for the first two model parameters were unavailable for anycongener (n = 29). Model-based estimates of these parameters were very close to the estimatesfor 6 species calculated from empirical data.