Abstract
A stochastic simulation model is investigated for the evolution of anti-predator behavior in birds. The main goal is to reveal the effects of population size, predation threats, and energy lost per escape on the evolutionary dynamics of fearfulness and boldness. Two pure strategies, fearfulness and boldness, are assumed to have different responses for the predator attacks and nonlethal disturbance. On the other hand, the co-existence mechanism of fearfulness and boldness is also considered. For the effects of total population size, predation threats, and energy lost per escape, our main results show that: (i) the fearful (bold) individuals will be favored in a small (large) population, i.e. in a small (large) population, the fearfulness (boldness) can be considered to be an ESS; (ii) in a population with moderate size, fearfulness would be favored under moderate predator attacks; and (iii) although the total population size is the most important factor for the evolutionary dynamics of both fearful and bold individuals, the small energy lost per escape enables the fearful individuals to have the ability to win the advantage even in a relatively large population. Finally, we show also that the co-existence of fearful and bold individuals is possible when the competitive interactions between individuals are introduced.
Highlights
Individuals within a single local population of the same vertebrate species differ in their propensity to take risks [1,2], and these differences in a range of correlated behavioral traits have been labeled as animal personality [2,3], or behavioral syndromes [4,5]
Ji et al found that the simple coexistence of two pure strategies is surprisingly impossible, and a small population is favorable to fearful individuals, while boldness is preferred in a large population [16]
In this paper, we develop a stochastic simulation model with overlapping generations to investigate the evolution of fearfulness and boldness, and our main goal is to illustrate the effects of population size, predation risks and energy lost per escape on evolutionary dynamics of fearfulness and boldness
Summary
Individuals within a single local population of the same vertebrate species differ in their propensity to take risks [1,2], and these differences in a range of correlated behavioral traits have been labeled as animal personality [2,3], or behavioral syndromes [4,5]. Two theoretical evolutionary game models are developed to explain how birds respond to the predation threat, i.e. the evolution of fearfulness and boldness [15,16]. Ji et al showed that the existence of a mixed ESS strategy is impossible [16] They explained that such phenomenon may ascribe to the ‘dilution effects’, i.e. individuals are safer because each individual in a large population has a relatively smaller chance of being the one attacked [17]. In this paper, we develop a stochastic simulation model with overlapping generations to investigate the evolution of fearfulness and boldness, and our main goal is to illustrate the effects of population size, predation risks and energy lost per escape on evolutionary dynamics of fearfulness and boldness. Since the maintenance of variation in personality in natural populations are still largely unknown [18], a possible mechanism for the coexistence of fearfulness and boldness will be developed through introducing the interactions between individuals
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