The eye spots of many prey animals deter predators from attacking, such as those of the peacock butterfly. In a new study, researchers from the Max Planck Institute for Chemical Ecology and Newcastle University show that the pattern of eye spots has an impact on prey survival. The deterrent potential of eye spots is greatest when they appear to be looking directly at a predatory chick. The most effective deterrent are concentric circles which subjectively appear to maintain eye contact regardless of the perspective from which they are approached.
Look me in the eye: in nature a matter of life or death
Visitors to an art gallery may be familiar with this effect: they feel observed or even followed by the eyes of the person portrayed everywhere in the room. This is called the “Mona Lisa effect” from the best known portrait with the described effect, and is created because the painter has precisely centered the pupils of the person portrayed. Some animals, including many fish and butterflies, have paired circular spots on their bodies that look a lot like eyes. “It seems that nature also uses the Mona Lisa effect. But in the animal kingdom it can be a matter of life and death,” says Hannah Rowland, head of the Max Planck Research Group on Predators and Toxic Prey at the Max Planck Institute for chemical ecology in Jena, Germany.
The directions of the gaze matter
To test the effect of the Mona Lisa and rule out a general deterrent effect of overt patterns, Hannah Rowland and her colleague John Skelhorn of Newcastle University developed a behavioral experiment with newborn domestic chicks that they trained to attack artificial moths for a mealworm reward. When the chicks had learned to attack their prey, they were presented with one of three different artificial moths: one with eyes whose central circles looked to the left, one with “eyes” that looked to the right, and one with perfectly concentric circles; therefore, they seemed to be looking straight ahead or to either side. Then the researchers built mini walkways (or rather walkways) that led directly to the food or approached the prey from the side.
The results of the behavioral experiments were not ambiguous: “The chicks approached more cautiously from the left when the eye spots appeared to be looking left. The chicks who approached from the right showed similar caution when the eye spots were moved. right. However, when the chicks approached the artificial eyes from the opposite direction, they quickly attacked the artificial moth and ate the mealworm. The chicks approached the moths with concentric circular eyes from all directions only with great caution, “sums up John Skelhorn.
Chicks perceive eye spots as eyes
Behavioral observations confirm the prediction that chicks perceive artificial eye spots as eyes. “Eye spots with concentric circles appear to stare at potential predators, such as our chicks, from many directions, just like portraits that appear to maintain eye contact no matter where you are in the room. This probably also explains why, in nature, the spots eyepieces have evolved independently in different animals to successfully deter enemies, ”believes Hannah Rowland.
Hannah Rowland heads the Max Planck Research Group Predators and Toxic Prey at the Max Planck Institute for Chemical Ecology in Jena. She focuses on predator-prey relationships, which have long served as models for studying adaptation and fitness in natural environments, and provide some of the best examples of parallel evolution. Hannah Rowland and her team use tools from small molecule chemistry, computational biology, physiology, molecular and cellular biology, and behavioral ecology to answer these fundamental questions: How do new traits arise and establish in populations? How do traits vary between levels, that is, between individuals within populations and between populations? What are the factors that promote and maintain trait variability? The answers to these questions are useful for identifying the ecological and evolutionary processes that underlie the interactions between organisms. They also help understand the origins of biodiversity and local adaptation and how biological systems respond to challenges in their environment.
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