Listen to part of a lecture in a biology class.

Listen to part of a lecture in a biology class.

Female: So last class we discussed how body parts of animals can have multiple functions. We focused on birds, how their feathers not only enable flight but also help regulate body temperature, and how beaks are used both for feeding and for sound production. Anyway, I wanted to give you one more example before we move on. It's from a recent study involving the mandibles or jaws of a species of ant from Costa Rica, the trap-jaw ant.

Female: Now, the trap-jaw ant gets its name from the way it uses its mandibles to capture prey. It brings its mandibles together in a very quick snapping motion. We've always known the mandibles snapped together very quickly, but a biologist named Sheila Patek figured out a way to measure the speed.

Female: Patek attached a high-speed camera to a microscope and placed some trap-jaw ants underneath the lens so she could videotape their jaws closing. And the tape showed that the mandibles moved at an incredible 233 kilometers per hour—no other predatory appendages are known to move that fast. But it gets more interesting: while doing some background reading to write up her research paper, Patek learned that people had observed trap-jaw ants leaping several centimeters into the air, apparently to escape from predators or other threats. Some people speculated that it was the ants' mandibles that enabled this jumping, but no one knew for sure since it happened so fast.

Female: Well, Patek did some calculations based on the speed of the mandibles and determined that by striking just one of its mandibles against the ground, a trap-jaw ant could generate a strike force in excess of three hundred times its body weight. Interesting, right? So to confirm her suspicions, she put some ants back under the microscope and filmed them again. And sure enough, it was the mandibles that were propelling the ants into the air. Trap-jaw ants actually employed two different types of jumps. In the first type, the escape jump, the ant strikes its mandibles against the ground, propelling itself vertically into the air and presumably out of a predator's reach. But a more common behavior is the bouncer defense jump, which might be used against an intruder approaching the trap-jaw ants' nest. Here, the ant strikes the intruder in a way that flings both insects away from each other in opposite directions. Interestingly, biologists who reported these jumps previously...um, they had speculated that the jumping might be an unintended side effect of the ants snapping their mandibles together, like especially with the escape jump, maybe the ant was trying to attack a predator but missed, and its mandibles hit the ground instead, flinging the ant into the air, um, unintentionally. But Patek’s videos suggest otherwise-they show the ants making a distinctive head movement before each jump, preparing for the jump, apparently.

Male: Wait, if the jaws move so fast, how would the ants avoid hurting themselves? Like when they're attacking another insect, what if the insect flew away and the mandibles slammed into each other at, what, 230 kilometers per hour? Couldn't that do a lot of damage to the ant?

Female: Patek wondered about this as well, but she discovered that the ants' mandibles actually begin to decelerate—slow down—just before they come together. To me, this suggests a type of self-protective mechanism. Like, if the mandibles were to miss their target, this built-in deceleration could prevent injury. Okay, so what have we got here? Insect jaws with two distinct functions: attacking prey and propulsion. But what can we safely conclude from Patek’s study- that the ants' jumping behavior is a genetic adaptation? Well, to draw this conclusion, we need to find out whether the escape jump really does help the ant avoid being eaten and whether the bouncer jump actually keeps intruders out of the ants' nest. It's certainly tempting to believe that jumping evolved to help the species survive, but we'll need some well-designed experiments to prove it.