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.
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.