A new "critter cam" has captured the speedy dives of Antarctic penguins as they hunt for prey.
The videos, captured by cameras attached to the birds, reveal that when going for fish, penguins use shallow dives, but may plunge deep into the frigid Antarctic waters to capture their favorite food, tiny shrimplike crustaceans called krill.
While studies of penguins' stomach contents have revealed fish and krill, exactly how the best-dressed animals capture them has remained a mystery.
Yuuki Watanabe and Akinori Takahashi of the National Institute of Polar Research in Tokyo wanted to understand exactly how penguins hunt. To do so, they attached critter cams to 11 Adélie penguins that live in Lützow-Holm Bay, Antarctica. The critter cams recorded about 85 minutes of activity from each animal as they held their breath and dived for prey. The findings were published today (Jan. 21) in the journal Proceedings of the National Academy of Sciences.
The team found that the penguins stuck to shallower waters to hunt a small, silvery fish called Pagothenia borchgrevinki, but made both shallow and deep dives for krill. That makes sense because "krill form swarms in the water column and appear in a highly variable density," the authors wrote in the paper.
While dives for fish produced a steady supply of food, dives for krill were more unreliable. [Image Gallery: Private Sex Lives of Penguins]
"This difference indicates that the success of penguins feeding on krill during a foraging trip depends on a small number of very successful dives, rather than a number of typical dives."
All in all, the penguins were impressive hunters, with no divers coming up empty-beaked. During about 88 minutes of diving (many individual dives), the Antarctic birds devoured 244 krill and 33 Arctic fish. The cameras also revealed that the penguins turned their heads quickly to engulf prey.
"Our movies showed that the foraging behavior of Adélie penguins is remarkably fast and efficient," the researchers wrote.
The findings could help explain why the population of a penguin colony of Adélies doesn't seem to change with the amount of time the birds hunt.