Dolphin Longevity and Long‐Term Site Fidelity in the Mississippi Sound: Insights From a 1982 Health Assessment

ABSTRACT

Due to its stable and safe environment, The Mississippi Sound (MSS) is home to one of the densest populations of common bottlenose dolphin ( Tursiops truncatus ) in the Gulf of Mexico. Being apex predators and sentinel species, the bottlenose dolphin acts as an ecological indicator within the MSS. In 1982, a health assessment was initiated to monitor the health of the dolphins and the MSS. Individuals were freeze branded and tracked in a long‐term mark‐tracking study. To monitor these individuals after the study, the Institute for Marine Mammal Studies (IMMS) conducted photo identification surveys to observe the dolphin population within the MSS. From the 50 dolphins originally freeze‐branded, 10 have been observed from 2011 to 2026. Seven are currently over 30 years old, and one is confirmed to be 47 as of 2026. Additionally, of the seven live dolphins, two have shown evidence of long‐term site fidelity. As some of the 1982 dolphins have confirmed re‐sightings 29 years after the initial freeze branding, it is vital to continue this monitoring effort through photo identification to accurately record dolphin longevity, long‐term site fidelity, and other dolphins that may be resident or transient. However, given the limitations of mark‐tracking studies, continued efforts are needed to confirm site fidelity and longevity. Ultimately, this study aims to create a better understanding of not only the dolphin's health in the MSS, but also the health of the ecosystem they live in.