Birds of prey fitted with cameras show how they search for their prey with random head movements to try to outwit hiding creatures below.
The birds would turn their head at unpredictable points in a similar manner observed in primates, they found. The research is published in The Auk: Ornithological Advances.
Suzanne Amador Kane of Haverford College in the US worked with falconer Robert Musters to fit a goshawk with a cap with a tiny camera. Musters was able to take advantage of the fact that the bird is used to having a hood over its head.
"He was able to adapt the hoods to very light-weight fibreglass eye openings," Kane told IBTimes UK. Falconers use hoods over the birds' heads to keep them calm while they are being transported.
Shinta's every movement
The goshawk – called Shinta – allowed the researchers to study its behaviour while walking on the ground, flying or being led by the falconer on his fist. They also used footage from libraries of footage collected from other hunting birds. They found the same behaviour in Shinta and in the archive footage.
"Instead of having regular probability of switching, sometimes the changes in gaze were distributed randomly," says Kane. This element of randomness is a great help to predators, as it makes prey unable to predict when they're likely to look in a different direction, she says. If the movement was regular then the prey animal would be able to anticipate the change of gaze.
"It's a compromise – think of old time movies. They'd have a hero and a villain dodging around a table. If you don't know what side they're going to turn or when, then you don't know whether to run one way or the other."
Kane also found that the motions were not completely random. "The raptor is also taking in information from its environment in a steady stream and using that info constantly updating whether to change its direction of gaze," she says.