Abstract

Age determination of bottlenose dolphins (Tursiops truncatus) is a valuable tool for stranding networks to continue conservation of this species. An aging technique assessing bottlenose dolphin pectoral flipper radiographs has been previously established. This technique is readily available, inexpensive, and non-invasive, but it has not been assessed for repeatability or agreement among users. Five observers of varying levels of experience, including a conservation marine mammal veterinarian, a board-certified veterinary radiologist, a certified aquatic veterinarian, a veterinary student, and a stranding technician, evaluated 114 bottlenose dolphin pectoral flipper radiographs from stranded dolphins in Mississippi. Each reviewer provided subjective scores for the 16 locations on the pectoral flipper identified previously to be associated with age. Agreement among the five observers was assessed by intra-class correlation (ICC) using PROC MIXED with SAS. The ICC was analyzed for each location and the sum score for all age classes. The individuals were then separated into perinates, calves, subadults, and adults and analyzed per age class. The results showed the level of agreement varied according to the age classes, as demonstrated previously with increasing root mean squared error in the older dolphins. High accuracy was observed in the perinate, calf, and subadult age classes. Of the 16 osseous locations, the delta bones had lower levels of agreement. We found that the aging technique benefits from some level of training, especially in older animals, but it is also yielding good results of repeatability and ease of useability by varying levels of expertise in younger animals.

Acknowledgements

This research was supported by the Mississippi Marine Mammal and Sea Turtle Conservation Recovery and Monitoring Program, which is funded by the National Fish and Wildlife Foundation under Mississippi Department of Environmental Quality Agreement No. 18-00081.

*Presenting author