Let's Talk with Randy Davis about Photographing Weddell Seals from Below the Ice
Part of Hall of Ocean Life.
Randy is a marine biologist who made a major contribution to the study of Weddell seals in Antarctica–he developed a camera and monitoring equipment small enough to attach to the backs of the seals. With this tool, he and his team can record on video the behavior of the seals below the sea ice, where they spend 90% of their time. Before Randy's camera, researchers could only speculate about the lives of seals beneath the ice. The work of Randy and his team has recently been featured in Newsweek, The New York Times, Science, Nature, and on CNN.
AMNH: What's so important about your field of study in Antarctica?
Randy: In some ways, our work is a basic science study–we want to know about Weddell seals simply to know more about them. But our work does have real conservation applications too; knowing more about the seals can help us better manage and protect this species, as well as other Antarctic species. We need to know about their habitat and requirements for survival in order to protect them.
AMNH: And what have you discoverved about Weddell seals?
Randy: My interest extends to all marine mammals and birds, but I chose to focus on the Weddell seal for three reasons. First, because of their environment. They live for much of the time under sea ice! We work in the open ocean, so we can't control the seals' movements. The animal is free to go, and to move far, through very deep water; they travel as far as 600 meters from the breathing hole. Since they're mammals, they need to come up for air, and they have to come back to a very particular ice hole to breathe. That hole allows us to keep tabs on them. I also prefer to study the Weddell seal because it is a good diver–the Weddells make deep and long dives. Also, Weddell seals are quite large. On average, they can reach 1,000 pounds. We like to think the technology we're using is very advanced, but it is not as small as we would like it to be. We need a large animal so it will not be encumbered by our camera equipment. Ultimately, the technology will allow us to extend the use of this technique to a wider range of animals. Another good thing about Weddell seals is their mild temperament!
AMNH: And what does the camera you developed allow you to do?
Randy: Weddell seals spend about 90% of their lives submerged; these new cameras allow us to travel with them underwater. We can watch predator-prey interactions; we can track 3-D movements with other sensors. Combined, these are powerful tools–we can study both their hunting strategies and the senses they use to track prey under-ice and underwater. In fact, we just published a paper on our observations, called, "Hunting behavior of Weddell seals."
AMNH: Is it all about what you see through the camera?
Randy: In addition to the cameras, we use sensors to track them. We are logging a lot of variables when they dive: we measure depth, swim speed, flipper stroke frequency, heart rate, body temperature, compass bearing. We also record audio so that we can hear any noises made by the seals underwater or any noises they hear. We use standard dead reckoning to compute the dive path, making a picture of the path with computers. We record the time with all of these variables so we can synchronize them all; that way we know what's happening when, and can figure out how everything interacts.
Field of Study Marine biology, particularly Weddell seals underwater
Favorite Middle/High School Subjects Drama
Least Favorite Middle School Subjects Science, especially biology
Major Influences "I got my diving certification at fifteen. That opened up a whole new world."
AMNH: That's a lot of data.
Randy: And a lot of work. When we're observing a diving animal, we have two shifts of people who each work fifteen-hour days. Since we work at a remote field camp, we also have regular responsibilities like camp maintenance and cooking. We run non-stop and keep the camera going all the time, even when the animal is sleeping. While the camera is running, we are always getting new instruments ready to be deployed or we are downloading data. We can process the data quickly enough so we can look at profiles within one or two hours. It's great that we can look at a first cut of the data while the camera is still running. It tells us if we have any equipment failures. Measuring the data is quite a challenge, but integrating all the data is just as challenging. We measure environmental variables too, such as light level and current direction. Our hope is to create virtual aquatic environments using all the data we collect. This would allow us to create models to test how changes in specific variables would affect everything else. Using the recorded data for the animal, we can see them move through this virtual environment. Of course, the richness and complexity of the virtual environment will depend on how much we can measure in our field research.
AMNH: And there must be implications for other animal studies.
Randy: Definitely. It is almost impossible to directly observe animals who live much of their lives submerged in the waters around Antarctica. Not much sunlight penetrates the waters there, and the animals are almost invisible once they submerge. We know very little about natural history under water so far, but technology like our camera can help us learn more.
AMNH: Can you describe some of the Weddells' adaptations? How are they different from other seals?
Randy: Size can be an adaptation, and the Weddells are very large. On the other hand, one of the Weddell's ecological counterparts in the Arctic, is the very small Ring seal. Sometimes it is an advantage to have a large surface area to body volume ratio to limit heat loss. Weddells are not too different from other deep-diving seals. They have a very large blood volume. They have an increased number of red blood cells; these are called hematocryts. Hematocryts can carry ten times as much oxygen as human red blood cells; that's important when you're staying underwater for such long periods of time. In other words, deep-diving seals can hold a lot of oxygen when they dive. They maintain an aerobic metabolism when diving, meaning that they keep using oxygen even when they're under water. This is only possible because they carry extra oxygen. But it's funny–if you forget about the extremity of the Antarctic marine environment, it's really a very constant environment. It's very cold, actually, near freezing, but that doesn't change much. There is no thermocline, meaning there's no distinct change in temperature as you go deeper under water. There's also not much variation over the course of the year. Once these animals adapt to 2ºC, they're okay. Marine organisms need to thermally insulate against water that is 2ºC, but they don't need to adapt to face changes in that temperature. In some respects, the Antarctic environment is very constant. For example, McMurdo Sound, has almost no ocean currents with its ice cover; it is a very constant environment. Weddell seals are thermally neutral in that environment and don't need to adapt to changes. In some ways, the Antarctic environment is not as challenging as environments that are constantly changing. Humans have tremendous environmental changes to cope with.
AMNH: Speaking of tremendous environments, what do you like about working in Antarctica?
Randy: People seem to either love the place or hate it. I love it. It is incredible, exciting, pristine, and undeveloped. There's a whole variety of undisturbed wildlife. It's an adventure to go there. It's especially great if you like field research and to draw. You can see so many wild animals in their natural environment. And of course there is almost no set-up quite that good for studying diving behavior and physiology. Our only problem now is that we are too dependent on constraining the seal to come back to one specific hole; that ultimately alters the animal's natural behavior. Ideally, we don't want the animal's behavior disturbed. It's also a tough job for us For the technique to work, you need a single breathing hole in the sea ice within a three-mile radius. It takes a while to find a location–this year it took us about two weeks. But no matter what, it's always exciting. Every time we get an instrument back from an animal, we don't know what we're going to see. Almost anything is going to be a surprise. It's wonderful to look at the tape for the first time.
AMNH: It must be incredible to watch a dive. What about your own diving in Antarctica?
Randy: The first time I dove was incredibly exciting. It was in 1981 at White Island, and I had wintered over. I was doing a Weddell seal study then too. Wintering over was a wonderful experience. The water was remarkably clear. Diving under the ice is so exciting and being out on White Island in the middle of winter, to my mind, is as close as you can come to being on another planet. We were in a small field camp–six or seven miles from McMurdo. We made the trip to McMurdo every week and a half or two weeks, but other than that we were on our own.
AMNH: Diving can be scary, how did you get into it?
Randy: I started getting interested in marine animals at an early age–around ten or eleven. I kept a variety of reptiles and then got into marine aquaria. Then when I was fifteen, I got my diving certification. That opened up a whole new world. In graduate school, I had a lot of support from my graduate advisor, who encouraged me to study the shared characteristics of marine mammals and birds–and to use diving in my work.