We are combining and examining the unique, long-term data sets collected by SDRP to determine and model how reduced prey affects foraging behavior, physiology, health, survival, and reproduction in bottlenose dolphins. The results of our efforts will help conservation managers predict how reduced foraging caused by human activities (such as noise exposure) will affect dolphin populations.
When individual animals respond to a stressor (anything that may cause an animal to change its physiology or behavior), what impact will such changes have on an entire population, and how will those changes occur? Those are two questions that have become increasingly important for conservation as the threats to marine mammals have become ever more subtle and pervasive. In addition, there is a need to know how exposure to multiple, seemingly-benign stressors can accumulate in an animal’s body and eventually affect reproduction and even survival. In particular, the Office of Naval Research (ONR) is interested in understanding how exposure to noise affects individuals, and how those effects are carried over into the population. To that end, the ONR-sponsored PCAD (Population Consequences of Acoustic Disturbance) working group developed a framework that helps us understand the links between different processes in individuals that lead to population-level changes (see figure). The framework is not limited to acoustic disturbance and recognizes that some types of disturbance are acute, causing almost immediate death or loss of young, or chronic, reducing the health of individuals over time which eventually reduces reproduction and survival.
To determine the relationships that link the processes together, we need an understanding of a species’ foraging patterns, behavior, energetics, health, survival, and reproduction. Therefore, it is essential to use well-studied species and populations to validate the approach. The long-term, extensive data collected by SDRP provide a very unique opportunity to study all aspects of the framework for a wild cetacean. By combining photo-ID, health assessment, necropsy, and behavioral data, we have started to piece together how health (such as white blood cell count and body mass index) affect survival and reproduction, which behavioral and physiological changes are linked to changes in health, and how different types of disturbance bring about changes in behavior and physiology. One of the critical behavioral changes we might see in animals exposed to sound is reduced foraging. While we do not want to perform experiments that would actually produce lower reproduction or survival, we can use data about natural disturbances that may create the same effect. In Sarasota Bay, we are investigating how red tide (which reduces prey) affects dolphin behavior, physiology, health, survival, and reproduction.
The results of these studies will aid in understanding the relationships we might see for species, or even other bottlenose dolphin populations, for which we have very little data. In addition, the results of these studies may aid in determining the most effective type of data to collect to determine the population consequences of disturbance.
This article was published on page 8 in the November 2014 issue of Nicks n Notches