Hawk

Hawk is one of the two contrasting behavioral strategies in John Maynard Smith’s hypothetical Hawk–Dove game, not a characterization of an individual animal. A Hawk escalates a contest and retreats only when seriously injured; its apparent strength gives it an advantage against a Dove, which threatens conventionally but does not inflict harm. Yet that advantage is conditional: as Hawks become common, the costs of Hawk-versus-Hawk contests make the strategy less successful. The model’s central point is that no strategy can be assessed apart from the population in which it operates.

Definition and Model

In the model, an animal is treated as following a pre-programmed behavioral policy, not as consciously calculating or choosing tactics. Hawk is the policy of fighting as hard as possible and withdrawing only when seriously injured. Dove, by contrast, engages in ritualized threat and eventually backs down without harming its opponent. The names are conventional labels for the model’s strategies, not claims about the actual behavior of the birds.

The contestants cannot identify one another’s strategy in advance and have no memory of earlier encounters with particular rivals. Each learns the opponent’s disposition only through the contest itself. This makes the outcome depend on the strategies present in the population, rather than on recognition, reputation, or deliberate planning.

Payoffs and Changing Advantage

The model assigns 50 points for winning, zero for losing, minus 100 for serious injury, and minus 10 for the time spent in a prolonged contest. These are illustrative values, treated as a proxy for contribution to gene survival; their purpose is to make the costs and benefits of alternative strategies explicit.

In a population made up entirely of Doves, contests end without injury. A winner receives 50 points but loses 10 for the time spent posturing, for a net score of 40; the loser also incurs the 10-point time cost. Since each Dove is expected to win half its contests and lose half, the average return is 15 points per contest. The peaceful strategy appears to work well while it is shared by the population.

A mutant Hawk entering this all-Dove population meets only Doves. It wins every contest and earns an average of 50 points, far above the Doves’ average of 15. Hawk genes consequently gain an advantage and spread. But their success changes the conditions that produced it: a Hawk can no longer count on facing a Dove as Hawks become numerous.

If the population consists entirely of Hawks, contests between them impose a serious cost. Each Hawk is expected to win half its contests for 50 points and lose half with a penalty of 100, giving an average return of minus 25. A Dove in this Hawk-dominated population loses every contest but avoids injury, earning zero. Dove genes therefore gain an advantage when Hawk becomes too common. The reversal is built into the payoff structure: Hawk excels against Dove, but its prevalence exposes it to costly competition from its own kind.

Stable Population Balance

The model does not require a continual, unlimited oscillation between the two strategies. With the stated point values, the stable population consists of five-twelfths Doves and seven-twelfths Hawks. At that ratio, the average payoff is equal for both strategies, so selection favors neither over the other. If the proportion of Hawks rises above seven-twelfths, Doves gain a relative advantage and the population tends back toward the stable balance.

This equilibrium is not evidence that the population has been organized for a shared good. The average payoff of an individual in the mixed population is 6.25, whether that individual is Hawk or Dove; by comparison, a Dove in an all-Dove population receives an average of 15. The hypothetical population could collectively do better if everyone remained Dove, but an individual Hawk could invade that arrangement and gain more. The model thus distinguishes a stable strategy balance, maintained by individual advantage, from a collectively more beneficial outcome.

Significance and Scope

Hawk illustrates the difference between winning a particular encounter and being successful across generations. Against Dove it wins outright, but the strategy’s payoff changes as its frequency changes. The game-theoretic analysis therefore replaces a simple ranking of aggressive and non-aggressive behavior with a question about the composition of the population and the costs attached to each kind of contest.

The book presents the examples as illustrations of individual behavior, not as sufficient evidence for a general biological claim. Its broader argument is that both apparent selfishness and apparent altruism can be explained through gene-level selection; the Hawk–Dove model contributes a separate demonstration of how strategic interactions can produce a stable population pattern without group selection. Hawk is neither an unconditional winner nor a moral type: it is a conditional strategy whose success is limited by the behavior it helps make common.