The shape of an animal’s eyes can tell whether that animal is a predator or prey, a new study suggests.
An international group of researchers learned what clues an animal’s pupils can provide them with when studying its behavior. We know that felines and snakes have vertically elongated pupils, while herbivore species such as cows and sheep have horizontally elongated pupils.
Berkeley researchers said that they even have a theory on why that happens. They said that grazing species need a panoramic view of the environment while they feed to stay away from predators. Their pupils are designed to allow them stay focused on the ground while grazing, while they also provide them with a lateral view that keeps them alert when a predator comes closer.
The horizontally-elongated pupils of grazing animals reduces to a minimum the incidence of blind spots which may prove often fatal. Researchers also believe that the geometry of their eye helps hunted animals find quicker an escape route because they can see out of the corner of their eyes where to go next or what obstacles to avoid during chase.
During the study, researchers analyzed more than 200 vertebrate species’ eyes. The research team took a close look at cats, dogs, snakes, mongooses, lions, cows, horses, rhinoceroses and so on. The team planned to learn whether the shape of the animals’ eyes indicated the role those animals played in the natural food cycle.
They got the idea from a 1942 study on the animals’ eye geometry, which had suggested that vertical-slit pupils were linked to a different structure of muscles and more light entering the eyes.
During their latest research, scientists found a series of associations. They learned that predators that lurk in bushes and wait for their prey to distance itself from the larger group had pupils that narrow vertically. That was the case of night prowlers, who also need their pupils to narrow excessively to capture the dim light available during nighttime.
Researchers also learned that domesticated cats can narrow their pupils by 135-fold, while humans can only reduce pupils by 15 times.
On the other hand, lions and tigers are also predators but they have round eyes and rounded pupils. Researchers explained that these predators do not have to prowl to reach their prey. They walk tall and are active hunters. They do not wait for their meal, they hunt it down relentlessly, the group argued. So, they need to both focus on their dinner but have a binocular view of the environment to estimate distances accurately.
Image Source: UCSC
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