Washington, February 22 : Zoologists at the University of Cambridge have found evidence against the 150-year-old theory that circular markings on creatures, such as butterflies, are effective against predators because they mimic the eyes of the predators' own enemies.
A study carried out by them instead suggests that circular spots, also known as 'eyespots', are protective because they are conspicuous features.
During the study, the researchers tested the response of wild avian predators to artificial moths, created from waterproof paper.
The research team had printed specific patterns-such as intimidating eyespots of different shapes, sizes and number, and with different levels of eye mimicry-on to the paper using a high quality printer.
Such paper moths were than pinned to trees of various species at a height of one to three metres in the mixed deciduous Madingley Woods in Cambridgeshire, UK.
To attract woodland birds, the researchers also attached an edible mealworm to each of the artificial moths.
The researchers observed that artificial moths with circular markings survived no better than those with other conspicuous features. They also noticed that the features of eyespots that most encouraged predators to avoid them were large size, a high number of spots, and conspicuousness in general.
"The birds were equally likely to avoid artificial moths with markings such as bars and squares as they were to avoid those with two eye-like markings. This leads us to conclude that eyespots work because they are highly conspicuous features, not because they mimic the eyes of the predators own enemies," said Martin Stevens, a member of the research team.
"This suggests that circular markings on many real animals need not necessarily, as most accounts claim, mimic the eyes of other animals," he added.
The study has been reported in the journal Behavioral Ecology.