Circular markings on creatures such as butterflies are effective against predators because they are conspicuous features, not because they mimic the eyes of the predators own enemies, according to research published today in the journal, Behavioral Ecology. Zoologists based at the University of Cambridge challenge the 150-year-old theory about why these markings are effective against predators.
Many animals possess protective markings to avoid predation, including patterns to reduce the risk of detection (camouflage), to indicate that the animal is toxic or inedible (warning colours), or to mimic another animal or object (mimicry and masquerade). In addition, many creatures such as butterflies, moths, and fish possess two or more pairs of circular markings, often referred to as eyespots. Many eyespots are effective in startling or intimidating predators, and can help to prevent or stop an attack. For the past 150 years it has been assumed that this is because they mimic the eyes of the predators own enemies.
However, recent work by University of Cambridge zoologists, Martin Stevens, Chloe Hardman, and Claire Stubbins, indicates that this widely-held hypothesis has no experimental support.
Stevens, Hardman, and Stubbins tested the response of wild avian predators to artificial moths, created from waterproof paper. Specific patterns, such as intimidating eyespots of different shapes, sizes and number, and with different levels of eye mimicry, were printed on to the paper using a high quality printer. These moths were then pinned to trees of various species at a height of one to three metres in the mixed deciduous Madingley Woods in Cambridgeshire, UK. Attached to each of the artificial moths was an edible mealworm as a temptation for woodland birds such as the blue tits, great tits, blackbirds, and house sparrows.
The zoologists discovered that artificial moths with circular markings survived no better than those with ot
|Contact: Martin Stevens|
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