Although recent advances in animal tracking technology have revealed large-scale movements of marine animals, little is known about fine-scale aspects of their behavior and ecology. Accelerometers represent a recent and likely transformative tool to study animal behavior by recording the frequency and force of swimming movements as well as the animal?s body orientation. These data can be used to quantify specific behaviors (e.g. resting, swimming, feeding, mating, escape responses, etc.) using wave-analysis techniques, and thus compile a continuous picture of an animal's activities for days at a time. Additionally, overall dynamic body acceleration (ODBA) has been shown to correlate strongly with oxygen consumption in a broad range of vertebrates, meaning acceleration may serve as a proxy for energy expenditure.
Despite the exceptional promise of accelerometers, controlled studies are required before they can be utilized to their full potential. This project will develop and refine the use of accelerometry on a large marine species that is amenable to captive experiments and that can be observed behaving naturally in the wild: the nurse shark, Ginglymostoma cirratum. Captive experiments will be used to evaluate different attachment methods and analyses for quantifying behaviors, tailbeat kinematics, and energy expenditure. Field experiments will be conducted to validate the results of captive trials and identify patterns of behavior and relative energy expenditure of wild animals.
This study will provide a methodological and analytical guide for the use of accelerometry to quantify behaviors and energy expenditure in large marine animals. It will also support a postdoctoral scholar and provide research opportunities for a graduate student and two undergraduate interns at Mote Marine Laboratory (MML) and Swansea University. A unique collaboration with Untamed Science will allow the project to be filmed and used to illustrate concepts for chapter-specific videos distributed with science textbooks to millions of K-12 students nationwide.
Although recent advances in animal tracking technology have revealed large-scale movements of marine animals, little is known about fine-scale aspects of their behavior and ecology. Accelerometers represent a recent, and likely transformative, tool to study animal behavior by recording the frequency and force of swimming movements as well as the animal’s body orientation. These data can be used to quantify specific behaviors (e.g. resting, swimming, feeding, mating, escape responses, etc.) using wave-analysis techniques, and thus compile a continuous picture of an animal’s activities for days at a time. Additionally, overall dynamic body acceleration (ODBA) has been shown to correlate strongly with oxygen consumption in a broad range of vertebrates, meaning acceleration may serve as a proxy for energy expenditure. This project developed and refined the use of accelerometry on large marine species and produced several key findings to advance the use of this technology to study marine vertebrates. We assessed the relationship between tailbeat frequency, acceleration amplitude, and ODBA, and determined that some species of sharks (such as blacktip sharks) increase their energetic expenditure primarily by increasing their tailbeat frequency and maintaining constant amplitude, whereas species such as the nurse shark show much more variability in tailbeat amplitude. Our results also show the need for high sampling rates in order to provide the best estimate of energy expenditure (ODBA). Tag attachment location and methodology were also tested, showing that attaching tags to the second dorsal fin produces larger changes in ODBA than when tags are attached to the first dorsal fin, but first dorsal fin mounted tags produce more precise measurements of body pitch. Attachment location should be determined by the primary question being addressed and the fin morphology of the given study species. We developed and refined a new technique for attaching and retrieving these data loggers from sharks and fishes, and also developed an attachment technique for ray species and showed how acceleration data can potentially be used to detect prey excavation behavior in rays. Our field experiments applying these new techniques to wild nurse sharks during the mating season showed that these animals exhibit repetitive yo-yo diving behavior when traveling, mate in deep (20-30m) water, and that some events in these deeper areas begin in midwater or near the surface. ODBA analyses showed that despite the fact that male nurse sharks spend more time swimming than females during the mating season, they do not expend significantly more activity-based energy than females. Females showed higher acceleration amplitude in their tailbeats than males, and this is likely due to the female mode of reproduction and the fact they are at their heaviest (full of ripe ova) during the mating season. This extreme difference in energy expenditure between males and females may explain why females seek refuge from males in shallow water rather than trying to continuously evade them at depth. This study supported a postdoctoral scholar and provided research opportunities for a graduate student and eight undergraduate interns at Mote Marine Laboratory (MML) and Swansea University. It produced a published book chapter on the application of accelerometers to elasmobranchs, three journal manuscripts in preparation, an undergraduate thesis, five scientific presentations at national and international conferences, and over 13 educational presentations given by the PI to the public and students ranging from elementary school through college. A unique collaboration with Untamed Science allowed the project to be filmed and published online to illustrate concepts for chapter-specific videos distributed with science textbooks nationwide.
