Optimal floating and queueing strategies: The logic of territory choice

This is a response to a recent article by Hanna Kokko and William J. Sutherland, who consider evolutionarily stable territory acceptance rules for animals that face the decision between settling on a poor territory now (which is then retained for life) or waiting for better habitat to become available later (taking a chance of dying before reproducing). In contrast to these authors, we argue that the evolutionarily stable threshold quality above which territories are acceptable does depend on whether individuals compete for a single territory (queuing) or for multiple territories (floating) and also on whether access to territories is determined by a hierarchy among waiting individuals. More specifically, we show the following: First, if the choice is between floating and settling, the evolutionarily stable acceptance threshold is such that threshold territories yield an expected lifetime reproductive success (LRS) of 1 – mu(F), the survival probability of a floater. Second, if the choice is between queuing and settling, the evolutionarily stable threshold may correspond to any LRS between 1 – mu(F) and unity. Third, the number of nonbreeding individuals in the population is maximized at a threshold of unity. In other words, the evolutionarily stable threshold does not maximize the nonbreeding fraction of the population. We argue that models of territory choice should carefully specify the mechanism of choice because some choice processes (e.g., indiscriminate habitat use above the threshold) do not admit an evolutionarily stable acceptance rule.