2001 Antarctic Expedition

The Foraging Biology of Weddell Seals

Notes from the Field

  (from Terrie M. Williams, Ph.D.)
text and photos copyright to T.M. Williams

 Research Assistant Matt Rutishauser prepares to ride a snowmobile
during a day of science on the Antarctic sea ice.  The goggles and ski
    mask help to prevent frostbite when traveling.  (Photo by T.M. Williams)

WEEK 4 – LABORATORY ON ICE

Teamwork for Science and Survival

After weeks of working and living together the research team has learned that each member plays an important part in the science and in the every day tasks of living in a remote field site.  We have three major scientific tasks this week that we divide among the team members.  Randy Davis and Bill Hagey spend their time calibrating the many scientific instruments that will be used on the Weddell seals during the diving experiments.  Lee Fuiman and Jesse Purdy map out the local ice and sea conditions including taking measurements of the currents, light levels and temperatures of the sea beneath our camp.  Matt Rutishauser and I conduct seal surveys and thermal measurements on the Weddell seals that have hauled out near our camp.   

Randy and Bill calibrate a dive sensor using a pressure station while Jesse and Lee deploy a current meter (yellow ball) and I take measurements on an adult seal.  (Photos by T.M. Williams and R.W. Davis) 

In addition to the scientific goals there are the day to day operations that ensure our survival:  radio checks with McMurdo Station, fueling heaters and generators, cooking meals, and the never ending task of shoveling the drifting snow.  Too much snow around the camp is a problem as it causes the sea ice beneath us to bend - over time a snow drifted camp could sink.   Everyone on the team takes their turn shoveling snow. 

There are many instruments that must be calibrated before we can begin our experiments with the seals.  Because Weddell seals can dive 20 times deeper than a human diver using SCUBA we let the seals carry the instruments with them to depth.   Each diving seal will wear an instrument package called a VDAP (pronounced Vee Dap, for Video Data Acquisition Platform) as they hunt for food.  The VDAP was created by Randy Davis and Bill Hagey, and includes a video camera, mini computer and many types of sensors.   

 All of the instruments are placed in a reinforced metal container that looks like a small SCUBA tank.  The container must be exceptionally strong to withstand the tremendous pressures that occur as the seals dive to depths exceeding 500 meters. The instruments and camera allow the scientists to study what the seal sees as it dives.  At the same time we can monitor how the seal swims, what temperatures it encounters, sounds that the seal may hear and even the seal's heart rate when it chases a fish.  

 A camera mounted on the head of the seal gives us a "seal's eye view"
 of the world below the sea ice. (Photo by R.W. Davis) 

Live and Death in Antarctica

While many of the instruments are being prepared Matt and I survey the area for healthy, adult seals that will be used in our experiments.  Our job includes identifying the males and females, and taking thermal measurements with our infrared camera.  As we conduct our seal measurements at the ice crack we find that the iceberg, B-15, has created unanticipated changes in the behavior of the seals in McMurdo Sound (see Week 2).  Rather than swimming to their usual pupping sites, pregnant seals arrive at the ice crack near our camp.  Suddenly, our expedition finds itself in the middle of a Weddell seal nursery.  Three Weddell seal pups are born at the ice crack.  We can't imagine a more difficult entrance into this world!  Born at temperatures near -17^oC with blowing snow on the Antarctic sea ice.   

Each day we count the number of seals at the ice crack and look carefully for the moms and pups.  Only two pups and their moms can be found after several days of looking.  Late in the week a storm brings in blowing snow and nearly all of the adult seals leave to seek shelter in the calm water below the ice.  Too young to know how to swim, one of the pups is left by himself in the storm.  Only one adult can be seen in the blowing snow - it is one of the mother seals staying close to her pup.  

A dedicated mom (Photo by T.M. Williams) 

After the storm Matt and I continue our seal surveys only to discover that the cold temperatures and snow have taken a toll on the abandoned pup.   We find the pup alone, frozen in a snow drift.

On the other side of the ice crack we notice that the second pup is still with his mom.  They have weathered the storm together and both are in good health.  While mom stretches out in the sun the pup continuously nurses on her rich, fatty milk.  He grows larger, fatter and healthier each day with the dedicated care of his mom.  

The events of the week remind the members of the research expedition that the line between life and death can be drawn quite thin in the Antarctic- we try to be especially careful as we continue our science on the sea ice.     

 Next week - Diving Seals

You can write to members of our Research Team at williams@biology.ucsc.edu