Elephant seals are in it deep due to climate change … deep in the ocean, that is. Elephant seals from Marion Island in the southwest Indian Ocean are swimming farther beneath the surface as their prey also moves into cooler, deeper waters.
"This prey is moving down to greater depths, presumably due to the increasing water temperatures, and this is forcing the seals to follow them," explained Horst Bornemann from the Alfred Wegener Institute, in a =6&cHash=6b674bb25e532fc802459386909f1b51']press release.
Bornemann and colleagues from the Mammal Research Institute fit more than 30 southern elephant seals (Mirounga leonina) with satellite transmitters. The transmitters are glued like beanies to the seals' heads. They measure dive depth, water temperature, and salinity on every dive, then beam that information to the marine biologists via satellite.
The results show that the seals dive deeper in warmer water.
"We therefore assume that the animals will find less prey in warmer water masses," explained Joachim Plötz, another biologist from the Alfred Wegener Institute involved in the study, in a press release.
Diving deeper means the seals have less time to feed, since they can only hold their breath for so long.
The next step of the study will be to prove that the seals are indeed feeding at greater depths. A follow-up study will fit the seals with a sensor that will record when they open their mouths.
The biologists noted that the Marion Island seals already live near the northern end of southern elephant seal territory. Further warming could put their survival on the island in jeopardy, though the massive marine mammals are listed as of Least Concern to the IUCN.
Male elephant seals are up to six times larger than females and rule over large harems of females. But some females have found a way to strike a blow for aquatic feminists by mating out at sea, where the sexes are on more equal terms, reported Discovery News.
Southern Elephant Seal on Macquarie Island. (Credit: Mbz1, Wikimedia Commons).
An elephant seal with a sensor on its head. (Credit: Joachim Plötz, Alfred Wegener Institute).
After placing the sensor on the animal's head, the biologists measure its body size. (Credit: Joachim Plötz, Alfred Wegener Institute).