Go Go Gadget Accelerometer

It fits in the palm of your hand, looks straight out of a James Bond film, and promises to help solve a long-standing problem for marine mammal researchers. It’s called an accelerometer, and it’s revolutionizing the way scientists observe feeding behavior in marine mammals.
The foraging habits of mammals that feed at sea are notoriously difficult to study, particularly in low-visibility polar environments. Yet researchers require data on feeding behavior to determine the well-being of marine populations — especially those in serious decline, like certain groups of Steller sea lions in the North Pacific.
Fortunately, the accelerometer promises to solve this quandary. This tiny electronic device can measure and record the acceleration of head and jaw motion, which in a recent study of hooded and harbor seals was shown to be the most prominent indicator of prey capture events.
Marine Mammal Consortium researchers decided to see if the gadget could detect prey capture as successfully with Steller sea lions. The research team was comprised of Morgane Viviant and Cristophe Guinet of France’s Centre National de la Recherche Scientifique, Andrew Trites and David Rosen of the University of British Columbia, and Pascal Monestiez of the Institut National de la Recherche Agronomique. The results of their study were recently published in Polar Biology.

High-tech Pinniped
The study involved outfitting a Steller sea lion at the Vancouver Aquarium with an accelerometer temporarily placed on its head and another under its lower jaw. Since the lower jaw is the only mobile part of a sea lion’s skull, the researchers reasoned that its movement (relative to the skull) would be the only one detectable during prey capture.
The Steller sea lion was the envy of her low-tech pool-mates. As she swam after herring, the accelerometers recorded each opening and closing of her jaws. A video camera synchronized to the accelerometers allowed the researchers to confirm that the movements detected by the accelerometers corresponded with individual prey capture events.

Overall, the researchers found that the accelerometers were an accurate means of recording prey capture through jaw motions. However, they also found that a single accelerometer attached to the lower jaw worked just as well as two devices.
Oh, the Possibilities
While the accelerometers in this experiment could not record the precise number of herring consumed, they successfully measured the number and timing of prey encounters — all crucial details for the researchers. Accelerometers placed on the body can also measure flipper beat frequency, and 3D models can even record the animal’s turning angle. The team concluded that this tiny device will give marine mammal researchers an easy and accurate way to judge foraging success and resource quality.

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Prey capture attempts can be detected in Steller sea lions and other marine predators using accelerometers. Viviant, M., A.W. Trites, D.A.S. Rosen, P. Monestiez and C. Guinet. 2010. Polar Biology 33:713-719. abstract We attached accelerometers to the head and jaw of a Steller sea lion (Eumetopias jubatus) to determine whether feeding attempts in a controlled setting could be quantified by acceleration features characteristic of head and jaw movements. Most of the 19 experimental feeding events that occurred during the 51 dives recorded resulted in specific acceleration patterns that were clearly distinguishable from swimming accelerations. The differential acceleration between the head-mounted and jaw-mounted accelerometers detected 84% of prey captures on the vertical axis and 89% on the horizontal axis. However, the jaw-mounted accelerometer alone proved to be equally effective at detecting prey capture attempts. Acceleration along the horizontal (surge)-axis appeared to be particularly efficient in detecting prey captures, and suggests that a single accelerometer placed under the jaw of a pinniped is a promising and easily implemented means of recording prey capture attempts.