The body or nutritional condition of dolphins can significantly affect survival, reproductive success, and susceptibility to disease through impacts on immune function. In addition, it can be a sensitive indicator of prey abundance and individual feeding success, as well as the presence of disease. Thus, assessing the body condition of animals is critical for monitoring the health of dolphin populations. However, current methods of measuring body condition in free-ranging dolphins require capturing, restraining and sampling individuals directly through capture-release health assessments, which are expensive and logistically complex, and are not feasible in many situations. With a grant from the Association of Zoos & Aquariums Conservation Endowment Fund (through funding from the Disney Worldwide Conservation Fund), and a fellowship grant from the Morris Animal Foundation, we designed and built a low-cost remote-controlled unmanned aerial vehicle (UAV) to remotely measure the body condition of cetaceans at sea.
The UAV, which has a digital camera, is designed to be launched from a small boat and to hover precisely over individual animals and collect photographs for detailed measurements of body size and shape (a technique called aerial photogrammetry), which then can be used to derive indices of body condition. Initial field testing of the UAV system was conducted over bottlenose dolphins being temporarily held in large net corrals during capture-release health assessments in Sarasota Bay. These initial trials enabled us to compare measurements (such as total body length and girth) obtained from the aerial photographs with those obtained directly from the animals during capture-release events and, thus, assess the accuracy of our technique.
Our next step will be to use the UAV system to collect measurements of body condition from resident bottlenose dolphins during year-round boat surveys in Sarasota Bay, and to conduct comparisons based on the animals’ sex, age, and reproductive class, as well as comparisons between seasons and between healthy and unhealthy individuals. Our novel health assessment technique could be used in the future to help determine whether capture-release health evaluations of bottlenose dolphins are warranted in areas of concern. In addition, our methodology could be applied to a wide variety of marine mammal species that have yet to be studied in this manner.
This article was published on page 10 in the November 2014 issue of Nicks n Notches