The researchers then released the animals into waters beneath the ice, and the camera-equipped seals recorded undersea activity as they swam to and from the site.
"The really wonderful thing about these animals," said Williams, "is that they are just so mild-mannered." When the seals resurfaced, the researchers removed the camera gear from them with minimal disturbance.
Underwater Cunning
Now, Fuiman's team has shifted to studying free-ranging seals, which the researchers locate through satellite and radio tags. Working with free-ranging animals is more of a gamble when it comes to getting the camera equipment back, said Fuiman, but it enables the researchers to observe the seals as they feed and interact with their own species wherever they roam.
"We need to understand the balance between predators and prey—we need to know who's feeding on what, and how much they are eating," said Williams. "These videos allow us to do this."
One of the most surprising findings for the scientists was the individual variation in hunting behavior. "Every animal seemed to have its own strategy for making a living," said Williams.
Yet how the seals are so skilled in finding food still remains a mystery. "It's cold and dark. The animals dive four to five hundred meters down while holding their breath, and are still efficient at finding food," said Williams.
Co-author Randall Davis of Texas A&M University in Galveston suspects that during summer, when the sun shines, the seals may find food by "silhouetting" prey. They dive down deep and look for prey that appear as dark silhouettes against the brighter underside of the ice.
But the seals also attack fish from above, Fuiman noted. He thinks the seals may detect prey by means of their whiskers, detecting the "wake" of fish as they pass by. "But this is a pure guess," said Fuiman. The video captured whisker movements as a seal pursued its prey.
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