Compensatory growth destabilizes adaptive personalities

Background/Question/Methods

Within a population individuals vary in their behavior.   Additionally, individuals are often consistent across time and between contexts in their behavior; this is known as personality.  One mechanism proposed to generate personalities arises from the fact behaviors are state-dependent on less labile traits, such as body size.  These traits could stabilize behaviour across time.  Additionally, positive feedback loops can  generate variation, for example by gape limitation since predation risk decreases as individuals become larger allowing them to forage more boldly in the presence of predation causing them to become even larger.  I suggest that canalized growth rates instead of compensatory growth rates will stabilize personalities, since compensatory growth allows individuals to greatly increase their growth rates in times of high resource availability.  This can lead to personalities converging, because individuals will converge in size.  In this study, I built a state variable model and used dynamic programing to solve how boldly individuals should forage and how much energy they should allocate to growth.  Using forward iteration, I performed experiments to see if the inability to perform compensatory growth stabilized personalities over the course of a life-time and between high and low predation environments.  

Results/Conclusions

I showed that compensatory growth destabilizes personalities due to individuals being able to quickly grow during periods of low predation risk.  This destroys the stabilizing effect of size on personality.   The experiments where individuals switched between high and low risk predation environments shows that personalities take less time to converge when individuals can complete compensatory growth.  I recommend that the study of compensatory growth and personalities should be integrated.  This work suggests that both differences in growth rates, and canalized versus compensatory growth is important for determining personalities.