Ahead of the pack: seals with satellite tags could gather data from oceans where few ships venture. Credit: M. BIUW

Marine mammals are ready to start collecting data on the remote polar seas, say biologists. They have been tagging animals as part of their work for decades, and now they say the satellite tags are sophisticated enough to provide oceanographers with valuable data too.

Mike Fedak of the Sea Mammal Research Unit (SMRU) says he hopes the tags will bring together oceanographers and marine biologists. “One of the most exciting things is that we have something to talk about with oceanographers, and they actually want to hear it,” he says.

The standard probes used by physical oceanographers are called CTDs, because they record conductivity, temperature and density. When dropped on lines or towed behind ships, they allow researchers to calculate the salinity and depth of the surrounding water, to track the distribution and movement of water masses.

The problem is that researchers are largely limited to areas where ships already travel. When it comes to the remote polar regions, especially the Antarctic, there is a dearth of data.

“There are a few floats out there but not much else,” says Lars Bohme, an oceanographer who has been working with Fedak's team at the University of St Andrews, UK. “There's a need for real-time data from this area, to develop models that in the short term can help predict weather and in the long term, climate change.”

Fedak and his colleagues worked with engineers at the SMRU to develop satellite tags containing miniaturized CTDs that can be carried by whales and seals. After a preliminary test on two beluga whales (Delphinapterus leucas) in Norway, a larger study called SEaOS (Southern elephant seals as Oceanographic Samplers) has convinced the researchers that the data are good enough to meet oceanographers' exacting standards.

The fist-sized tags were attached to the heads of about 70 elephant seals (Mirounga leonina) at four breeding areas around the Southern Ocean over the past three years. During the Antarctic winter, the seals dive roughly 40 times a day to between 300 and 800 metres, to hunt for fish and squid. When the animal surfaces, data collected from its dive are transmitted to the Argos system of satellites. These relay the information to researchers in real time.

“The tags provide precise, accurate data,” says Bohme. He is using information from SEaOS to profile the Southern Ocean's currents, and says he is now popular with other oceanographers, who are keen for data from the under-sampled Southern Ocean.

“Oceanographers treated it with scepticism at first because it seemed wacky,” adds Fedak. “But tests of the tag's accuracy have shown this can work.”

Jamie Morison, an oceanographer at the University of Washington's Polar Science Center in Seattle is convinced. “This is a really useful idea,” he says, although he adds that seals will not be able to do everything. “I'm interested in processes underneath the ice,” he says. “These animals won't go where the ice is too thick for them to come up and breathe.”

SEaOS will finish collecting data in January 2006. Fedak hopes to work with researchers in eight other countries to use seal and whale species in hard-to-reach polar areas.