Resolving feeding dynamics of marine predators using a multi-sensor biologging approach

Foraging- an organism's process of hunting, capturing, and consuming food- provides essential nutrients and energy needed for survival. Predator-prey interactions are key in structuring the trophic hierarchy in ocean biomes. Since quantifying the foraging process in free-ranging animals remains challenging, developing a biologging technique that measures feeding in freeranging marine predators could greatly advance our knowledge of trophic dynamics and ecosystem structure. While the methodological, analytical, and technological limitations to quantifying predator-prey interactions in the ocean are daunting, the physical act of a predator attempting and successfully foraging on a prey item can be readily measured in jaw movements. In this study, we developed a biologging approach that combines accelerometer and magnetometer sensors to measure feeding events. A magnet was affixed to the dorsal surface near the upper mandible, and the magnetic field strength could be used as a robust proxy for jaw angle. We conducted a series of multi-day trials on captive smooth dogfish (Mustelus canis) and collected (n=60) feeding events and conducted a field test on two wild animals. We found that this approach successfully resolved distinct feeding events and facilitated analysis of fine-scale kinetic variations, such as jaw angle, prey-handling, recovery time, and bite frequency. This research represents a crucial step toward accurately identifying and quantifying feeding events in wild marine predators, enhancing our understanding of predator-prey dynamics and feeding hotspots in marine ecosystems.