Sealed and delivered
Long-term population study of Weddell seals makes some 'super' discoveries
Posted February 10, 2012
Thierry Chambert and Jesse DeVoe maneuver their snowmobiles over the fast ice close to the coast of Ross Island’s Hut Point Peninsula, making a series of turns as if climbing mountainous switchbacks but on a flat, if irregular, surface.
The trail they’re following is nearly invisible to the first-time visitor, with an occasional tattered flag on a bamboo stick the only indication that there’s any rhyme or reason to each right and left turn.
But they’ve been to this place called Hutton Cliffs dozens of times over the last two months to count and weigh Weddell seals, and they are intimately familiar with every crack and bump in this ever-evolving icescape — the fast ice attached to the coast reshaped by tidal forces.
“We go there every day, so we know where to step,” said Chambert, a thick French accent drawing out each word, as if in added emphasis.
But the 2011-12 field season for the researchers involved in the Weddell seal population dynamics project — now in its 44th year as one of the longest such mammalian studies in the world — started out in unfamiliar territory.
Large cracks in the dynamic first-year sea ice forced the crew to move its base camp south of the Erebus Ice Tongue, a glacier that extends about 10 kilometers into McMurdo Sound. Several times early in the season, some team members even had to leap across the crack by helicopter to access the northern colonies of what’s known as the Erebus Bay region.
The addition of bridges for light vehicles like snowmobiles eventually solved the problem, according to Robert Garrott , a co-principal investigator, along with fellow Montana State University (MSU) professor Jay Rotella , on the long-term study.
In more than four decades since Don Siniff , now a professor emeritus at the University of Minnesota , helped pioneer the study of Weddell seals, researchers have carried out their annual census despite lean budget years, summer storms and other wild extremes that come with working in Antarctica.
More than 20,000 Weddell seals have been tagged and more than 180,000 re-sightings have been logged in the project database. All the pups that have been born into the Erebus Bay population since 1973 have also been tagged, meaning about 80 percent of the seals found grunting and growling as they roll around on the sea ice are tagged. About 65 percent are of known age.
Siniff had originally pioneered the use of radio transmitters in the late 1960s (post-vacuum tubes) to gain insight into seal behavior. The first radio transmitters were put on the colony at Hutton Cliffs, about 13 kilometers from McMurdo Station . From the radio signals, the researchers learned, for example, how long the seals spent on the surface versus in the water.
Eventually, the techie part of the project was discontinued, and Siniff focused on the population dynamics, producing one of the longest running datasets on a long-lived mammal. Weddell seals can live for 30 or more years. [See sidebar — Getting techie: Weddell seal population dynamics study employs different technologies.]
Siniff’s legacy goes beyond mere data, however. “The project has a history of training some very successful professionals,” noted Garrott, himself a former graduate student under Siniff.
A professor in MSU’s Ecology Department , Garrott competed for the opportunity to take over the long-term study a decade ago, recruiting colleague Rotella, also a professor in the Ecology Department. The duo added a new dimension to the study to understand how the ecosystem affected the seal population, which can swing wildly from one year to the next.