A Generalized Population Model based on Indian River Lagoon Dolphins

For over a decade, researchers at Harbor Branch Oceanographic Institute have conducted
surveys of the population of bottlenose dolphins, Tersiops truncatus, in Indian River Lagoon
along the east coast of Florida. I have constructed a detailed 4-stage population model using the
statistical program R. The model is used as a tool for conducting a viability analysis that projects
the dolphin population into the future by analyzing the relationship between birth, calf survival
and adult survival rates. The model also includes a power analysis, which compares survey
frequency to expected confidence intervals in estimating abundance. The model shows a strong
chance of viability over a 50 year time span, primarily due to the large population size of
approximately 700 adult dolphins. The population is vulnerable to long periods of decline if
birth, calf or adult survival rates fall below certain thresholds. The sensitivity analysis, based on
the partial derivatives of the eigenvalue with respect to each matrix element, shows that the
population is most sensitive to changes in adult survival, followed by birth rate and calf survival.
Overall, the model simulates the future impacts of demographic change, and thereby provides a
tool for conservation efforts.