Penguins' efficient hunting techniques captured on cameras
Japanese scientists have filmed intimate details of Adelie penguins' feeding behaviour.
They have gained a unique insight into the birds' hunting techniques using video cameras and accelerometers attached to free-swimming penguins.
They found that Adelie penguins adopt different strategies depending on whether they were hunting fish or krill.
Although previous studies had examined Adelie penguin's (Pygoscelis adeliae) foraging style using video apparatus or sensor technology, results were limited.
The footage confirmed that penguins move their heads relative to their body when they capture prey, lead scientist Dr Yuuki Watanabe from the National Institute of Polar Research in Tokyo, Japan, told BBC Nature.
The penguins' foraging area is largely covered by marine ice and their primary food sources include two species of krill and Pagothenia borchgrevinki - a fish whose blood contains antifreeze proteins.
The Antarctic krill (Euphausia superba) is a shrimp-like crustacean that grows to approximately 6cm long. Antarctic coastal krill (E. crystallorophias) lives farther south than any other species of krill.
The show found that when capturing krill, the penguins swam upward then changed direction at the point of predation, making darting movements with their head.
The team discovered that Adelie penguins could catch krill at a rate of up to two krill per second, despite krill displaying escape behaviours.
They also found that the camouflage defence of the fish P. borchgrevinki didn't work with foraging Adelie penguins.
The penguins were regularly able to capture the fish from below - the direction from which the fish is camouflaged against the backdrop of marine ice.
The findings are published in the journal PNAS.