A camera on the back of an Adélie penguin documents its hunting strategy when it attacks a medium-sized fish, as well as the prey’s defense strategy. Analysis of the images shows that penguins could use an interception technique on this type of fleeing prey.
How would we react if a tyrannosaurus species attacked us as we were leaving for work? What would be its technique? To tire us out or intercept us? Would we be quick to flee or prone to prostration? The best way to study a predator and its prey is to attach a camera to the predator’s back and then view the images.
Soma Tokunaga, a Japanese behavioral biologist, and his colleagues have discovered, using footage of Adélie penguins hunting, that they intercept medium-sized fish during their flight. Video recordings taken below the water’s surface were recently published in the journal Ecology and suggest that Adélie penguins are moving toward the future position of the fish in the water to capture it. This technique differs from stalking, which consists of moving in the direction of the prey in a constant manner.
They support their hypothesis with two other elements, the environment is open, the fish are not constrained by obstacles, rocks or reefs, and the fish do not change direction while they escape. The penguins could therefore predict its course and intercept it.
This fish is an Antarctic notothenioid or ice fish, known for the physiological ability of its blood to resist freezing. The images show that 6 times out of 8 the intercepted fish adopts a C-shaped posture and does not struggle. In the case where the fish escapes from the bird’s beak, the images show that they keep this position.
The authors believe that “this behavior is a voluntary posture,” they write. This defensive posture would prevent the penguin from ingesting it, a reflex known in the aquatic larvae of stoneflies – a prey of salmon -, as well as in some marine fish.
The four hours of recordings were taken during the 2012-2013 austral summer and also described the collection of krill or small fish, while the penguins were diving, in open water or under the ice.
Camille Lin, PolarJournal
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