We know the ages of most of the bottlenose dolphins in the Sarasota population.
Knowing the age distribution of a population is critical for conservationist.
Age can help us understand if the population is healthy or not, and whether it is likely to increase or decrease in the future.
Also, age is a crucial measure for determining how environmental contaminants accumulate over time in dolphins.
But how do we learn their ages? Often, we know it because we have observed new calves since our study began in 1970, and we’ve watched them grow up.
If we don’t know when a dolphin was born, we can estimate age by looking at one of its
100 or so teeth. This involves removal of a tooth under local anesthesia by a trained marine mammal veterinarian. Over the years, we have found this to be a simple and safe procedure.
This method has allowed us to estimate that Nicklo was 64 years of age in June 2014, and is the oldest documented bottlenose dolphin to date. A very few males, like Jimmy Durante, reach 50 years of age, and F154 was 51 years of age in June 2014.
An expert, such as Dr. Aleta Hohn of the National Marine Fisheries Service, prepares the tooth and carefully examines the dentine and cement through a microscope. Like the growth rings in trees, dolphin teeth have annual layers called “growth layer groups.” Annual layers are added from the outside in, gradually filling up the cavity in the middle of the tooth. The layers can be counted to estimate age. This technique was refined and validated with SDRP dolphins and is now used world-wide to estimate dolphin age.