Prior to our research on bottlenose dolphin milk, so little was known that researchers were unable to even determine if milk composition changed over lactation as it does in other mammals. Our research on captive dolphins has demonstrated that the milk of dolphins does in fact change as lactation progresses. We have also completed the analyses of milk samples collected from wild dolphin mothers in Sarasota Bay, Florida. Our data indicates that milk composition is similar between wild and captive dolphins although milk protein levels were consistently higher in the wild dolphins. For the first time, our team has also applied a novel biomarker technique to study foraging in wild dolphin calves. We have learned that calves of at least one and a half years of age ingest solid food along with their mother’s milk, indicating that they have at least acquired rudimentary foraging skills by this age. It is likely that mothers are actively training their young in the school of prey capture.
We have made significant strides to broaden our understanding of dolphin calf nutrition but our findings emphasize a number of questions that remain unanswered. For example, we are especially interested in learning how much, or the quantity of milk dolphin calves need to survive. This has not previously been determined in a cetacean, but is necessary information to fully address the energetic costs of lactation. How dolphin nutrient stores change over the course of lactation is also unknown. We only have minimal data available on the balance between food intake and nutrient depletion while feeding young dolphins. Much is yet to be learned about the volume of milk ingested by calves and the transfer of energy from the mom to the calf.
To date, the novel biomarker technique has only been applied to a few marine mammal species. We have been able to confirm that calves of at least one and a half years actively forage, but the precise age calves begin to forage remains unknown. Access to fresh carcasses of young dolphin calves combined with the application of this technique should allow for a precise age determination in the future.
Research on marine mammals not only helps us gain a better understanding of dolphin biology, but is a reflection of the status of marine ecosystems. Dolphins are large and conspicuous animals that feed at high levels in the oceanic food web. There remains a great deal to be learned about these magnificent species and how we can best act to protect marine mammals and their environment.