U.S. Department of Commerce


Date of this Version



Published in MARINE MAMMAL SCIENCE (2003), 19(4):630-649


Data gathered from 220 stranded bottlenose dolphins (Tzmiop tvuncatlls) in the Indian River Lagoon system, Florida, were used to derive a life table. Survivorship curves were fit to the data using Siler’s competing-risk model and a maximum likelihood approach. Population growth was estimated to be between r = 0.0 and 0.046 based on the observed numbers of stranded dolphins. Variance in survival rates was estimated using an individual-based, age-structured population projection model. We estimate that the overall annual mortality rate for this population was 9.8% per year. Sex-specific differences in survivorship were apparent with females outliving males. The overall mortality curve resembles that of other large mammals, with high calf mortality and an exponentially increasing risk of senescent mortality. The inclusion of live-capture removals of individuals from this population did not significantly affect the estimation of survival parameters for most age classes.