Nicole Teutschel at Long Marine Lab, CA -- One of the best things about being a marine biologist is getting to ask questions about the oceans, and then figuring out how to get the answers. Many of the tags we deploy give us little clues, or puzzle pieces that we then get to put together in an attempt to discover the bigger picture. Professor Ken Yoda of the Graduate School of Environmental Studies at Nagoya University in Japan was scratching his head trying to figure out a way to learn more about one of the missing pieces in the elephant seal puzzle: foraging. Techniques like analyzing isotopes of tissues, blood and whiskers combined with scat samples gives us a rough idea of elephant seal diet. What we don’t know, is when the seals are eating.
Ken Yoda, PhD.

Learning more about the when and where of foraging can help us better understand why elephant seals travel so far, and how they’re able to gain so much weight despite their high activity level. They swim 10 months a year and travel more than 20,000 miles! Are seals foraging throughout their dive trip, or only when the reach the middle of the North Pacific? Do the seals eat as they dive to the depths of the ocean, or only when they get to a particular depth do they start to search for food? After we answer those questions, we can move on to other questions such as: Does location and depth of elephant-seal foraging change over time, age or sex? Do these locations pose a potential conservation problem? In other words, are they foraging where fish stocks are declining due to people overfishing them?

In the past. researchers have tried looking at time-depth-recorder (TDR) tag data to try and figure out foraging patterns. Yoda decided to do something a little different. He deployed accelerometer tags. Accelerometer tags measure the change in speed over time. They've been used to study locomotion on penguins (Yoda et al. 1999), salmon (Tanaka et al. 2001), flatfish (Kawabe et al. 2003), Weddell seals (Sato et al. 2003), and even the land-locked Baikal seal of Russa (Watanabe et al. 2004).

The E-Seal Team on the day we put out the first accelermeter (from Left): Randall Davis, Daniel Crocker, Jason Hassrick, Ken Yoda, Luis Huckstadt,   Cory Champagne, Nicole Teustchel, and Daniel Costa. We all look pretty happy because Yoda's study required us to find a seal that was especially skinny, signifying that she was ready to go...which could have been a daunting task! Yoda wanted that tag in the ocean as soon as possible to increase length of time that the accelerometer would be taking measurements. Luckily we found a the perfect skinny seal quickly, she was later named "Diel".

What makes this especially useful is that the tags are small enough to fit on the bottom of an elephant seal's jaw. The change in jaw speed can illustrate when the seal is opening and closing its mouth…such as when it's catching or eating squid.

Yoda glues an accelerometer onto Diel's lower jaw. This little device is so small that it won't get in the way of her looking for food or eating it. The tag was attached to a piece of mesh and glued to the fur using epoxy, the same way that satellite tags are glued on. This seal was also equipped with a GPS satellite tag, a time depth recorder (TDR) tag and a radio tag.

When the seals come back to the beach in April and May, we’ll recover the tags, and Yoda will check out the data to see if we can learn more about elephant-seal foraging behavior. We hope it will give us another glimpse into their secret lives at sea.