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Tag: seals

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    Mapping the Oceans With Seals

    Elephant seals are harbingers — canaries in the coal mine — for climate change. A long-running experiment tracks northern elephant seal populations using a combination of sensor tags and field measurements. With the miniaturization of sensors, a tagged seal can provide a wealth of data for scientists: foraging paths, temperature and salinity data, behavioral patterns, ecological data, and even information on the species around the seal. This video delves into this treasure trove, explaining how and what we’re learning from this species, especially as they navigate our changing climate. (Video and image credit: Science)

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  • Hunting By Whisker

    Hunting By Whisker

    Seals and sea lions often hunt fish in waters too dark or turbid to rely on eyesight. Instead, they follow their whiskers, using the turbulence generated by a fish’s wake. The vortices shed by the fish cause the seal’s whiskers to vibrate, giving them sensory information. To better understand what a seal can derive from this, a recent experiment looked at what a thin whisker can pick up from an upstream cylinder.

    As expected, the strength of the whisker’s vibration fell off the farther away the cylinder was. But the researchers found that, if they moved the cylinder quickly — like a fish trying to dart away — the vibration of the whisker was stronger. They also found that the whisker was sensitive to misalignment. If the cylinder was placed ahead and to the side of the whisker, the whisker would still vibrate but would do so around a different equilibrium position. That result implies that a seal can get information both about the fish’s speed and direction, simply from the twitch of its whiskers. (Image credit: seal – K. Luke, illustration – P. Gong et al.; research credit: P. Gong et al.; via APS Physics)

    Illustration of a seal following a fish versus the experiment, a whisker following a cylinder's wake.
    Illustration of a seal following a fish versus the experiment, a whisker following a cylinder’s wake.
  • Meltwater Tracking Via Seal

    Meltwater Tracking Via Seal

    Monitoring meltwater from Antarctic glaciers is critical for understanding our changing climate, but such remote and inaccessible regions are tough to collect data in. So researchers are turning to local workers to help them gather data. By collecting and analyzing data from seal tags, researchers have mapped new seasonal variations in meltwater flows around Pine Island Glacier. Although the seals are somewhat tough collaborators — they rarely swim exactly where the researchers would like them to — their winter activities are revealing data researchers could never have collected on their own. (Image credit: Y. Rzhemovskiy; research credit: Y. Zheng et al.; via Gizmodo)

  • Wild Gray Seals Clap Back

    Wild Gray Seals Clap Back

    Here’s a paper that cries out for fluid dynamical/acoustical follow-up: wild gray seals have been observed signaling underwater by clapping their forefins. As you can hear in the video, the sound is quite loud and carries well underwater. The biologists who observed the behavior postulate that it’s used by males during breeding season to ward one another off and to signal strength to nearby females.

    Although many species (including humans) slap against the water surface to generate noise, we don’t know of other species producing such a loud clap entirely underwater. The clap resembles the motions used by seals for propulsion, though the results are obviously quite different. I know plenty of researchers already looking into seal propulsion — here’s your future work! (Image and video credit: B. Burville; research credit: D. Hocking et al.; via Gizmodo)

  • The Sensitivity of a Seal’s Whiskers

    The Sensitivity of a Seal’s Whiskers

    Harbor seals and their brethren have a superpower that lets them track their prey even without sight or sound. It’s their whiskers, which are sensitive enough to follow the trail left by a single fish thirty seconds earlier. The secret to the whisker’s sensitivity lies in its shape. Instead of a uniform, circular cross-section, the seal’s whisker is oval-shaped and its width varies along the length in a wavy pattern. So unlike a straight cylinder, which vibrates when towed through water, the seal’s whiskers are unperturbed by their own movement. They shed only weak vortices and do not vibrate as a result.

    But, if you expose the whiskers to any external turbulence, like the vortices trailing a fish, the whisker ‘slaloms’ back-and-forth in time with the wake. That motion gets transmitted to the nerves in the seal’s cheek, carrying potential information about both the size and speed of the wake’s originator. Researchers hope similar bio-inspired whiskers could help underwater vehicles track schools of fish or locate underwater drilling leaks. (Image credit: M. Richter; video credit: MIT; research credit: H. Beem and M. Triantafyllou; via the Economist; submitted by Russ A. and Kam-Yung Soh)