Nature
PUBLISHED
Tiger beetles run so fast their vision cannot keep up. A study of how they respond to this challenge could help explain other animal behavior, as well as provide tips for robot vision.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.If you thought the fastest animal on land was a cheetah, you'd only be partly right. The tiger beetles can't manage the same absolute speed, but certain species can travel 120 to 170 times their body length per second, not far behind the peregrine falcon. This is often considered a record, although earlier this year a faster relative speed was reported.
The beetle's eyes aren't large enough to take in the light required to produce clear images at such speeds. Even if they did, their brain might not process it. This raises a problem: How do they know when to pounce on their prey when they can barely see? If potential dinners would run in a straight line through an obstacle-free landscape that might not be a problem, but they don't.
Earlier this year, Cornell researchers demonstrated the beetle's antennae form part of the answer, but there is more to it than that.
Tiger beetles capture their prey with terrifying mandibles. But running with mouthparts wide open in a cluttered environment is hazardous. Therefore, they need to open their mandibles only when they are getting close to their goal.
“We're asking in what situations do the mandibles open and close," says Dr. Daniel Zurek of the University of Pittsburgh. "They're trying to catch something, so they want to be sure that their jaws are open and close on contact."
Zurek dangled a piece of plastic on a string and had the beetles chase it. After filming their behavior in super slow motion he reported in Biology Letters that the beetles open their jaws when the target, blurred as it may be, expands rapidly in their field of view, indicating they are getting close.
If the prey starts to get away from them (easier for an item on a piece of string than a smaller insect) the beetles close their jaws again.
Zurek concludes that the beetles operate on visual rules that apply even in dynamic environments, and this could be useful for programming machines that will interact with moving objects.
