Hunger Games: is honesty always the best policy for animals?
- Transfer
As a result of evolution, peacocks developed a complex tail for attracting females. Scientists use game theory to study the role of honesty and cheating in animal communication.
Imagine that you are an inexperienced peacock, which turned out to be weak as a result of poor heredity or nutrition. You hope to attract a female who is only interested in the length of your tail. Growing up a long tail would increase your sexual attractiveness, but this burden may prevent you from running away from a predator that a healthier male would avoid (and if they eat you, your chances of mating will drastically decrease).
Will evolution evolve you to honesty, with the result that you grow a small tail that reflects your actual physical condition? Or does it make you risk your life by growing extravagant plumage disproportionately to you?
The best strategy for peacocks - and other animals in the process of their communication, from gazelles demonstrating agility in front of lions, to chicks asking for a worm - can be determined using game theory, a mathematical discipline that studies how different decisions affect the outcome of a game. In an evolutionary game where the goal is to leave offspring, a notorious lie will not be the best strategy. If the tails of peacocks always lied, the females would stop paying attention to them. But crystal honesty, which has always been considered the best strategy, may also not be perfect - judging by recent evidence.
In a new studyGame theorists have shown that partial honesty can be the best animal communication policy. Thanks to computer simulations of evolving populations, the researchers found that over time a certain unchanging relationship between the amount of honesty and lies was established, where the “signaling devices” (peacocks) are not completely honest, and the “recipients” (females) are not completely trusting. “In fact, there is a stable situation in which communications are partly honest,” says Kevin Zolman of Carnegie Mellon University, lead author of the work.
Incomplete honesty works so well in theory that if biologists can observe it in practice in peacocks and other animals, this theory can replace the old, but not working, idea of how the animals communicate.
“An interesting idea, supported by a theoretical model, which you should try to apply to the asking behavior of meerkats,” wrote Marta Manser [Marta Manser], a biologist from the University of Zurich. “But such a test is not easy to conduct directly.”
As explained by Mancer, it is quite difficult to control all the factors of animal behavior - and therefore, check the predictions of the new theory and compare it with the old one.
Decades canonical explanation of animal communication was the principle of handicapfirst proposed by evolutionary biologist Amotz Zahavi in 1975. According to this principle, all signals among animals have their price, but animals are honest, because the cost of deception is too high. Weak peacocks do not grow long tails for the same reason that the poor do not buy Maserati: it is too expensive. The poor man risks becoming bankrupt, the peacock - to die.
In 1990, the game theorist Alan Grafen [Alan Grafen] mathematically provedthat the handicap principle is stable in terms of evolution. In a game in which a signal increases the attractiveness of a signaling device, but decreases its survivability (as in peacocks with huge tails), a balance between cost and benefits is achieved if all signaling devices are completely honest. And the liar who entered the game at this moment - a weak peacock with a long tail - cannot gain an advantage. And with the support of game theory, the handicap principle became a “panacea,” as Zolman says. When observing the communication of animals, scientists assumed that their behavior is costly.
But the problem was that sometimes there was no cost. “If the handicap principle is correct, people thought that they could see the cost of signaling in the various signal systems of nature,” says Michael Lachmann, a theoretical evolutionary biologist at the Institute of Evolutionary Anthropology. Max Planck. “But it didn't work out always.”
Consider a chick who wants to grow as large and strong as possible. He must beg for food from his parents, regardless of the feeling of hunger, unless begging is not expensive. But experiments show that for most species of birds, begging does not require any special expenses. “It’s easy to do, and it’s not attractive to predators,” says Zolman.
In the game with Grafen's alarm, the low cost of signals should lead to an avalanche-like increase in asking for from chicks, which, in turn, will lead to the disappearance of the meaning of such an action, and to the disappearance of the action itself. In order for the non-costly signals to remain stable, evolution must play a different game.
In a 1997 paper, the theorist biologist Carl Bergstrom [Carl Bergstrom] and colleagues uncovered another riddle: for honesty to be stable, the signal cost — even honest — must be so high that signalmen and signal-takers would be better off if that signal did not appear in the course of evolution. Scientists are not clear how this situation could arise. “A simple definition of an evolutionarily stable strategy is not enough to prove that evolution really went along with it,” said Bergstrom of the University of Washington.
In the January issue of Proceedings of the Royal Society B, Zolman, Bergstrom and Simon Huttegger of the University of California showed that the model of incomplete honesty solves both problems. It is evolutionarily stable for both costly and cheap signals, and its equilibrium point is reached in computer simulations.
In peacocks, it can work like this: high-quality males always grow long tails, but low-quality ones will be varied - some will grow long tails, some will be short. “If you see a peacock with a long tail, the probability of its high quality is greater, but there is no certainty,” says Zolman. And peacocks are not tempted by every long tail strolling nearby. "If she sees a long tail, she sometimes decides to mate with him, and sometimes she rejects."
Incomplete honesty works in a similar way in the case of inexpensive signals. Hungry chicks always ask for food, and not very hungry sometimes they also ask for it. “Parents should sometimes, but not always, feed the begging chick, and should never feed the chick who does not ask for anything,” says Zolman.
In theory, such a strategy is advantageous, but to find out whether real birds use it, further research is needed. Hugh Drummond, a biologist at the National Autonomous University of Mexico, who studies the interaction of chicks and parents in blue-footed booby, claims that parents-booby sometimes ignore active chicks up to 20 minutes and then suddenly burp a piece of food — and such the behavior seems to be consistent with the model of incomplete honesty. “The thing is the inconstancy of the responsiveness of the parents,” Drummond asks, “or are they just waiting for the food to digest enough before burping?”
Blue-footed booby
Biologists must unravel these subtle interpretations of animal behavior in order to answer more general questions about the evolution of honesty and deception. “Although the predictions of Zolman’s model are artificially cleaned,” says Drummont, “their checks can be bogged down in ambiguities.”
Imagine that you are an inexperienced peacock, which turned out to be weak as a result of poor heredity or nutrition. You hope to attract a female who is only interested in the length of your tail. Growing up a long tail would increase your sexual attractiveness, but this burden may prevent you from running away from a predator that a healthier male would avoid (and if they eat you, your chances of mating will drastically decrease).
Will evolution evolve you to honesty, with the result that you grow a small tail that reflects your actual physical condition? Or does it make you risk your life by growing extravagant plumage disproportionately to you?
The best strategy for peacocks - and other animals in the process of their communication, from gazelles demonstrating agility in front of lions, to chicks asking for a worm - can be determined using game theory, a mathematical discipline that studies how different decisions affect the outcome of a game. In an evolutionary game where the goal is to leave offspring, a notorious lie will not be the best strategy. If the tails of peacocks always lied, the females would stop paying attention to them. But crystal honesty, which has always been considered the best strategy, may also not be perfect - judging by recent evidence.
In a new studyGame theorists have shown that partial honesty can be the best animal communication policy. Thanks to computer simulations of evolving populations, the researchers found that over time a certain unchanging relationship between the amount of honesty and lies was established, where the “signaling devices” (peacocks) are not completely honest, and the “recipients” (females) are not completely trusting. “In fact, there is a stable situation in which communications are partly honest,” says Kevin Zolman of Carnegie Mellon University, lead author of the work.
Incomplete honesty works so well in theory that if biologists can observe it in practice in peacocks and other animals, this theory can replace the old, but not working, idea of how the animals communicate.
“An interesting idea, supported by a theoretical model, which you should try to apply to the asking behavior of meerkats,” wrote Marta Manser [Marta Manser], a biologist from the University of Zurich. “But such a test is not easy to conduct directly.”
As explained by Mancer, it is quite difficult to control all the factors of animal behavior - and therefore, check the predictions of the new theory and compare it with the old one.
Decades canonical explanation of animal communication was the principle of handicapfirst proposed by evolutionary biologist Amotz Zahavi in 1975. According to this principle, all signals among animals have their price, but animals are honest, because the cost of deception is too high. Weak peacocks do not grow long tails for the same reason that the poor do not buy Maserati: it is too expensive. The poor man risks becoming bankrupt, the peacock - to die.
In 1990, the game theorist Alan Grafen [Alan Grafen] mathematically provedthat the handicap principle is stable in terms of evolution. In a game in which a signal increases the attractiveness of a signaling device, but decreases its survivability (as in peacocks with huge tails), a balance between cost and benefits is achieved if all signaling devices are completely honest. And the liar who entered the game at this moment - a weak peacock with a long tail - cannot gain an advantage. And with the support of game theory, the handicap principle became a “panacea,” as Zolman says. When observing the communication of animals, scientists assumed that their behavior is costly.
But the problem was that sometimes there was no cost. “If the handicap principle is correct, people thought that they could see the cost of signaling in the various signal systems of nature,” says Michael Lachmann, a theoretical evolutionary biologist at the Institute of Evolutionary Anthropology. Max Planck. “But it didn't work out always.”
Consider a chick who wants to grow as large and strong as possible. He must beg for food from his parents, regardless of the feeling of hunger, unless begging is not expensive. But experiments show that for most species of birds, begging does not require any special expenses. “It’s easy to do, and it’s not attractive to predators,” says Zolman.
In the game with Grafen's alarm, the low cost of signals should lead to an avalanche-like increase in asking for from chicks, which, in turn, will lead to the disappearance of the meaning of such an action, and to the disappearance of the action itself. In order for the non-costly signals to remain stable, evolution must play a different game.
In a 1997 paper, the theorist biologist Carl Bergstrom [Carl Bergstrom] and colleagues uncovered another riddle: for honesty to be stable, the signal cost — even honest — must be so high that signalmen and signal-takers would be better off if that signal did not appear in the course of evolution. Scientists are not clear how this situation could arise. “A simple definition of an evolutionarily stable strategy is not enough to prove that evolution really went along with it,” said Bergstrom of the University of Washington.
In the January issue of Proceedings of the Royal Society B, Zolman, Bergstrom and Simon Huttegger of the University of California showed that the model of incomplete honesty solves both problems. It is evolutionarily stable for both costly and cheap signals, and its equilibrium point is reached in computer simulations.
In peacocks, it can work like this: high-quality males always grow long tails, but low-quality ones will be varied - some will grow long tails, some will be short. “If you see a peacock with a long tail, the probability of its high quality is greater, but there is no certainty,” says Zolman. And peacocks are not tempted by every long tail strolling nearby. "If she sees a long tail, she sometimes decides to mate with him, and sometimes she rejects."
Incomplete honesty works in a similar way in the case of inexpensive signals. Hungry chicks always ask for food, and not very hungry sometimes they also ask for it. “Parents should sometimes, but not always, feed the begging chick, and should never feed the chick who does not ask for anything,” says Zolman.
In theory, such a strategy is advantageous, but to find out whether real birds use it, further research is needed. Hugh Drummond, a biologist at the National Autonomous University of Mexico, who studies the interaction of chicks and parents in blue-footed booby, claims that parents-booby sometimes ignore active chicks up to 20 minutes and then suddenly burp a piece of food — and such the behavior seems to be consistent with the model of incomplete honesty. “The thing is the inconstancy of the responsiveness of the parents,” Drummond asks, “or are they just waiting for the food to digest enough before burping?”
Blue-footed booby
Biologists must unravel these subtle interpretations of animal behavior in order to answer more general questions about the evolution of honesty and deception. “Although the predictions of Zolman’s model are artificially cleaned,” says Drummont, “their checks can be bogged down in ambiguities.”