Testing a visual illusion in toads

Along with a research team at Purdue University, I decided to test the motion dazzle effect, which is a visual illusion that makes animals with high-contrast coloration (like black and white stripes) more difficult to capture while fleeing than solid-colored animals. This effect has been used to explain the evolution of complex color patterns in zebras and many other animals. However, the effect had previously only been tested in humans and birds, and never with live prey animals.

We decided to test the motion dazzle effect with cane toads as predators and house crickets as prey. Toad vision is highly attuned to small moving objects, which made us think that they might not succumb to this illusion as easily as birds and mammals.

Photo by Geena Darnell

Figure by Jimmy Peniston

To conduct our experiment, we first painted the crickets with either solid, striped, or clear patterns and then presented them to the toads either individually or in mixed-pattern groups to determine which ones were most likely to get eaten.
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Unlike previous tests of the motion dazzle effect, the toads in our experiment had equal capture success for solid and striped prey. However, since toad vision is highly specialized for detecting moving objects, we decided to also measure how much time each cricket spent jumping around rather than sitting still. We found that the toads' ability to capture prey was highly dependent on prey movement, regardless of the prey's color pattern. Overall, our study revealed the importance of considering the predator's unique visual system when studying the evolution of their prey species. ​