SECTION 4—ASSESSMENT OF EXTINCTION RISK 4.1. Description of Extinction Risk Assessment Approaches

To assess extinction risks of loggerhead DPSs, we conducted two independent analyses. The first analysis used the diffusion approximation approach based on time series of counts of nesting females or nests (Lande and Orzack 1988, Dennis et al. 1991, Holmes 2001, Snover and Heppell 2009). This analysis provided a metric (susceptibility to quasi-extinction or SQE) to determine if the probability of a population’s risk of quasi-extinction is high enough to warrant a particular status listing (Snover and Heppell 2009). This approach is based on stochastic projections of observed trends and variability in the numbers of mature females at various nesting beaches. The second approach focused on determining the effects of known anthropogenic mortalities on each DPS with respect to the vital rates of the species. Anthropogenic mortalities were added to natural mortalities and possible ranges of population growth rates were computed as another metric of population health. This approach focused on how additional mortalities may affect the future growth and recovery of a loggerhead turtle DPS.