Are there particular health measures that can be used to predict how well a dolphin population is doing? Are some health values tightly linked to survival and reproduction? Do easy-to-measure health values correspond to other health values that are difficult to measure? The answers to these questions have far-reaching implications for many dolphin populations because they can help researchers target specific
, which may allow them to predict if a population is growing or declining, and if they should be concerned about its future. Using extensive datasets on Sarasota Bay dolphins, we looked at 47 different health measurements and their relationship with population-level survival and reproduction. We also explored the relationship between a measure of body condition, post-nuchal depression (also called “peanut head” because there is a divot behind the blowhole that makes an animal’s head peanut-shaped), and other health measurements. Post-nuchal depressions can be readily identified from photographs, so there is no need to handle the animal. Therefore, it has the potential to be a very useful measure of health in areas where animals cannot be captured.
The body-mass index (BMI, a value showing how far an animal is from the average mass for its length) is linked with survival. In other words, animals that are too skinny or too fat for their length have lower survival. The relationship was found using health samples from live, rescued, and dead animals as well as the long-term photo-ID data. Mother-calf separation was more likely when adult aldosterone levels where high. Unlike terrestrial animals, aldosterone may be an indicator of longer-term stress in marine mammals, indicating mothers and calves are more likely to separate after prolonged stress. Preliminary results show post-nuchal depression is not reliably related to poor health or body condition. Results emphasize the importance of collecting photo-ID data as well as data from dead and rescued animals.
This article appeared on page 5 of the 2018 SDRP Annual Report, Nicks n Notches.