Elephant Seals Revealed

Small sensors attached to 85 southern elephant seals (Mirounga leonina) to track their movements and collect data about their marine environment have revealed that they adopt different strategies to find food.

The new sensor technology has allowed an international team to witness, for the first time, how elephant seals conduct themselves in the wild. The sensors, the size of a pack of cards, were attached to the seals' heads. UK scientists from the University of St. Andrews in Fife, Scotland, and the British Antarctic Survey published the research this week in Proceedings of the National Academy of Sciences. (The device is attached with glue but falls off when the seals molt. "They are small devices for such large and powerful animals, and have no impact," the university said in a statement.)

Elephant seals (Photo: Mike Fedak)

The seals were tagged at the islands of South Georgia, Kerguelen and Macquarie in the Southern Ocean, and at the western coast of the Antarctic Peninsula. The Southern Ocean is one of the most productive in the world, primarily as a result of short, intensive spring phytoplankton blooms.

The majority of the seals from South Georgia remained in the Antarctica Circumpolar Current, avoiding Antarctic waters such as the Weddell Sea, whereas seals from other locations preferred waters much closer to the Antarctic continent. Regions of upwelling of nutrient-rich deep waters were clearly favored, the university said.

Data was transmitted back to land via satellite. The sensors' conductivity-temperature-depth satellite relay data logger (CTD-SRDL) provided high-accuracy temperature and salinity readings via satellite. They were designed and built by the Natural Environment Research Council (NERC) Sea Mammal Research Unit at St. Andrews and and Valeport Ltd. UK, a Devon, England, maker of hydrometric and oceanographic instruments.

The Sea Mammal Research Unit at St. Andrews University led the research. Author Mike Fedak, a St. Andrews biology professor, said, “These data are really exciting. This new technology has allowed us to see where the seals go and understand their behavior in the context of different characteristics of water in the Southern Ocean. The majority of animals from South Georgia fed within the Antarctic Circumpolar Current, but seals from other locations had a very different strategy and visited colder waters nearer the continental shelf. This approach helps us to understand current population trends, where the animals forage and predict the availability of food under various climate change scenarios."

Mike Meredith, head of the Atmosphere and Ocean Group at British Antarctic Survey, said, “The Southern Ocean is the hardest place in the world to obtain oceanographic data, especially during the wintertime. The seals acted as ‘samplers’ to collect data from deep seas that we couldn’t ordinarily access due to their remoteness and harsh environments. Understanding how these animals respond to their environment is fundamental in predicting how they may respond to climate change and the consequent shifts in ocean circulation and ice dynamics.”

Sea temperature is predicted to increase by around 2°C in the next 100 years. If Antarctic animals can’t adapt, they are unlikely to be able to cope in warmer water or to compete with species that will inevitably move into the region as temperatures rise, the university said.

The research was funded by the NERC.

For more information ,visit: www.st-andrews.ac.uk/