Steller Sea Lions Say Ahhh for Science
INTRO: Steller sea lion populations in western Alaska have declined by some 80 percent since the 1960s. Scientists trying to understand why believe the sea mammals may not be getting enough fish to eat. To test the theory, one scientist first had to get the sea lions to open wide and say ahhh. Doug Schneider has more in this week’s Arctic Science Journeys Radio.
STORY: Russ Andrews studies animals that live mostly out of view to people. Animals like sea lions and elephant seals dive too deep for scientists to follow. To learn more about them, he needed special instruments that monitor their activities. Such instruments are available for land animals, but not for animals that dive hundreds, even thousands, of feet deep in the ocean. So, Andrews taught himself a bit about electronics and set to work building the instruments he needed; soldering together bits of wire, computer chips and circuit boards.
ANDREWS: “Mostly I’ve had to do it just because there were certain biological questions that I wanted to ask and then I realized that the tools I needed just didn’t exist. I had to do this, even though I wasn’t naturally inclined to do. I didn’t have any experience. I didn’t take any classes. I learned the hard way.”
Andrews is a marine biologist at the Alaska SeaLife Center in Seward, Alaska, and a researcher at the University of Alaska Fairbanks School of Fisheries and Ocean Sciences. One of the questions he’s trying to answer is whether sea lions are finding enough food to eat. But since Andrews can’t follow a sea lion around and watch it catch prey, he came up with a device that--in a roundabout way—does.
ANDREWS: “The stomach temperature monitor allows us to roughly quantify how much food they eat each day.”
About the size and shape of a hot dog bun, the temperature sensor Andrews built is pushed down into the stomach of an anesthetized sea lion. The device sends continuous readings to a small recorder inside a waterproof container that’s glued to the sea lion’s back.
ANDREWS: “Sea lions are like most mammals. It has a warm body temperature. We call them an endotherm or a homeotherm, meaning that they generate their own body heat. But they’re living in this cold ocean eating fish that are the same body temperature as their surroundings. When a warm blooded sea lion ingests a cold fish, its stomach temperature has to drop. So if I put this stomach temperature recorder in, whenever it is swimming around and catches a cold fish, its stomach temperature goes from about 37 Celsius to about 30 Celsius. And then depending on how big that fish is (the stomach) will warm up really quickly or it will warm up more slowly (as the food is digested). So I can compare those curves, that is how quickly the temperature drops and how quickly it warms back up to get a rough idea of how much fish was ingested.”
Along with the stomach temperature sensor, other devices he makes or adapts tells Andrews where, when, how deep and how fast the sea lion is diving to find food. Over time, he’s able to build a profile of what life is like for sea lions.
Andrews put the stomach temperature recorders in female Steller sea lions from a declining population around Seguam Island in the Aleutians, and a relatively stable population around Lowrie Island in Southeast Alaska. He says that in this very limited experiment, which sampled only a few animals during one summer month, sea lions from both groups often had a cold stomach—meaning they’re getting enough to eat.
ANDREWS: “Are sea lions having a hard time finding fish? Basically, what we found in this one small study where we could do everything identically was that it didn’t seem to be the case at all. Both populations were having no problem finding fish.”
It’s too soon to say whether sea lions overall are finding enough to eat, however. Anderson would like to extend his studies to a larger number of sea lions in different locations. Ideally, he says it would be nice to know not just when and how much fish they eat, but also what kind of fish the sea lions are eating. Are sea lions eating relatively lean pollock or fatty salmon, for example? Knowing this may help scientists gauge the health of sea lions. A device that measures pH in a sea lions stomach might work, but so far he hasn’t been able to build a reliable one.
ANDREWS: “That might have been something that would have given us a little clue to at least the type of fish, but not necessarily the exact species. Some species are more difficult to digest are more fatty and cause the stomach to respond differently. But they’re much more complicated than just a simple temperature sensor.”
Andrews admits to being a bit of a techy when it comes to his scientific contraptions. He says he next plans to mount small cameras on Stellers to see exactly what kind of fish they’re preying on.
OUTRO: If you’d like to learn more about Russ Andrews’ research or Steller sea lions, come to our Web site at www.asjnews.org This is Arctic Science Journeys Radio, a production of the University of Alaska Sea Grant Program. I’m Doug Schneider.
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Thanks to the following individual for help preparing this script:
Russ Andrews, Marine Biologist
Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks. The shortcut to our ASJ news home page is www.asjnews.org.
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