Fetal survival of common bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida

Reproductive success is an important aspect of dolphin population health as it is an indicator of the trajectory for the population into the future. Concerns about potential reproductive impacts of environmental contaminants have stimulated increased interest in measuring reproductive success in wild dolphin populations. One measure of reproductive success is the survival of fetuses to parturition. Pregnancy determination for wild dolphins, including differentiation of pregnancy stage, is possible during capture-release health assessments through application of diagnostic ultrasound to evaluate fetal development and viability, estimate gestational age, and measure anatomical structures. As a first step toward understanding reproductive success in utero, we combined pregnancy detections during health assessments with subsequent observational population monitoring to examine and evaluate pregnancy outcome for well-known, long-term resident common bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida. In total, 0.83 (95% CI = 0.52 to 0.99) of detected pregnancies were documented as resulting in live births. The use of ultrasound for systematic pregnancy determination provides a useful tool for measuring an important component of reproductive success. Application of this approach for conservation of wild populations benefits from the establishment of baseline values such as the estimates provided herein for the reference population of bottlenose dolphins residing in Sarasota Bay, Florida.