When my brother and I were young, we were very careful to share the last bit of dessert equally. It's not that we were particularly magnanimous. In their wisdom, my parents instituted a rule in our house: one of us would divide the snack in half, and the other would select his half. "You cut, I choose" was a common phrase in the Goldman household throughout the 1990s. The rule ensured that we'd each be as equitable as possible when in the role of divider. The kitchen ruler was retrieved on more than one occasion. If I thought I could have gotten away with scarfing down the last cookie without him noticing, I'm sure I would have done it. And I would not have been sorry.
Imagine, however, what would have happened if my brother had decided to keep the entire last cookie for himself and run into the living room with it. Here's one way he might have kept me from snatching my fair share of the snack: find a decent hiding spot, and if I got too close, he could run back into the kitchen. Once back in the kitchen, if I got too close to him, he could have gotten up and run back to the living room. This is called a "stimulus-response rule." Eventually, being the bright child that I was, I would have caught onto the pattern and found a way to block his path from one room to the other, increasing the chance of getting some of the dessert.
Here's a better method that my brother could use to protect his treat: keep his eyes on me the entire time, always moving away from me so that the distance between us was, on average, fixed. If I go right, he goes left. If I move towards him, he backs up. Short of backing him into a corner, my efforts would be futile. That's because instead of using a small set of predictable actions, my brother could call upon a wider range of behaviors. Its much harder for a thief to learn how you protect your food if your behaviors are variable than if they are predictable. This is called a "cybernetic rule."
Last year, Heather C. Bell and colleagues from the University of Lethbridge showed that rats use a pattern of "robbing and dodging," respectively, in order to steal or protect food. The defender, who has in his or her possession a small bit of food, dodges the robber's incursions through a combination of lateral motion and in-place pivoting. Rats accomplish this by using a cybernetic rule. They maintain a constant distance between themselves and other rats, freeing them up to use a nearly infinite combination of movements. The rats are playing constant defense rather than waiting to defend their food from an impending theft.
Bell then turned her attention to the field cricket, Teleogryllus oceanicus.
If you wanted to choose two different species for studying to uncover parallels when it comes to decision-making, you might pick Asian and African elephants, for example, separated by thousands of kilometers and approximately seventeen million years of evolution, but roughly anatomically equivalent. Or maybe wolves and their domesticated cousins, dogs. Or meat-eating chimpanzees and fruit-eating bonobos, two species of apes closely related to humans with vastly different social structure and diet. Or chimpanzees and bottlenose dolphins, with nearly identical social structure but tremendously different sorts of habitats.
You might not think to pair rats with crickets. But these two animals may have more in common than it seems, according to a new article published this month in the journal Animal Behaviour.
First, the researchers needed to be sure that the crickets who were assigned the role of robber would be sufficiently hungry, and therefore motivated to steal the food, and that the crickets assigned the role of defender would be motivated to protect theirs. They did this by not feeding them for six days (crickets can survive without food for up to seven days), and by keeping them isolated from eachother. Then, on the seventh day, a pair of crickets - one robber and one defender - were placed into a small, dark enclosure. The researchers placed a tiny bit of food in front of the defender. Then, the fight began.
Welcome to Cricket Fight Club. The first rule of Cricket Fight Club is: you do not talk about Cricket Fight Club. The second rule of Cricket Fight Club is: you do not talk about Cricket Fight Club.
The trial began when the defender picked up the food, and ended when one of the crickets ate it. Each pair was tested three times. Then, the researchers used their video recordings to analyze the actions of each cricket to determine how she guarded her snack.
Just like rats, the crickets kept their food away from interlopers by using a cybernetic rule. In fact, they used the same exact rule: move so that the other crickets are always a fixed distance away. Rather than escaping from robbing attempts, both rats and crickets continuously attempt to avoid the possibility of robbery in the first place.
Arthropoda, the phylum to which crickets belong, and Chordata, which counts the rat among its members (as well as humans, and all mammals, birds, fish, amphibians, reptiles, and more) diverged some five hundred million years ago. Rats have some fifty-six million neurons, while crickets have around a hundred thousand. Rats have four legs, crickets have six. Rats maintain their hold on food with their two front paws, which means that they're limited to the use of their hindlegs for defense. In contrast, crickets hold their food with their mandibles, a pair of jaw-like structures that they use to hold, crush, or cut food, freeing up all six legs for defensive maneuvering. Despite such enormously different body plans and nervous systems, food guarding in these two divergent species is governed by the same rules. That two different organisms, each with its own unique quirks complexities, are in some ways indistinguishable speaks to the efficiency - and beauty - of evolution.
For more from the cricket fight club:
Heather C. Bell, Kevin A. Judge, Erik A. Johnson, William H. Cade, & Sergio M. Pellis (2012). How is a cricket like a rat? Insights from the application of cybernetics to evasive food protective behaviour Animal Behaviour, 84, 843-851 DOI: 10.1016/j.anbehav.2012.07.005
Bell, H., & Pellis, S. (2011). A cybernetic perspective on food protection in rats: simple rules can generate complex and adaptable behaviour Animal Behaviour, 82, 659-666 DOI: 10.1016/j.anbehav.2011.06.016