The body or nutritional condition of dolphins can significantly affect individual survival and reproductive success. In addition, it can be a sensitive indicator of prey abundance, feeding success, and the general health of an individual. 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, 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 dolphins at sea. The six-rotor UAV, which has a digital camera mounted below it, is designed to be launched from a small boat and to hover precisely over individual animals to collect photographs for detailed measurements of body size and shape (a technique called aerial photogrammetry). Initial field testing of the UAV system was conducted in 2014 over dolphins being temporarily held in large net corrals during capture-release health assessments in Sarasota Bay.
More recently, in response to FAA restrictions and uncertainties regarding deployment of UAVs, we have been using a pole-mounted camera system to collect overhead images of Sarasota Bay dolphins. The pole camera was constructed by engineers at Woods Hole Oceanographic Institution under the guidance of Michael Moore. It makes use of a long carbon fiber pole that was previously used to deploy tags on large whales. With the pole camera mounted on the SDRP’s pontoon boat R/V Challenger, we collected overhead images of more than 60 dolphins this summer both during capture-release health assessments and during boat-based surveys while animals were free-swimming in the bay.
The images will enable us to compare body size and shape measurements (such as total body length and girth) obtained from the aerial photographs with those obtained directly from the animals being temporarily restrained during capture-release events, to assess the accuracy of our technique. The images will also allow us to compare measurements based on the animals’ sex, age, and reproductive class, as well as between healthy and unhealthy individuals. Our novel health assessment technique could be used to help determine whether capture-release health evaluations of bottlenose dolphins are warranted in areas of concern, and it could be applied in the future to a wide variety of marine mammal species that have yet to be studied in this manner. This system was used to provide body condition data for treatment of a stranded bottlenose dolphin undergoing treatment at Mote’s dolphin hospital.
This article appeared on page 21 in the December 2015 issue of Nicks n Notches.