Evolution of natal and breeding dispersal: when is a territory an asset worth protecting?

Lay Summary Often offspring leave home-disperse-while their parents stay. Why exactly should individuals become more settled in adult life? Reluctance to move enables keeping hold of an asset (a territory) already owned. We show, however, that variation in the quality of locations and the accuracy of information about sites matters. Nonowners of territories possess "invisible assets" of being able to compete for sites more freely than owners, and this can make owners sometimes move more.Evolutionary models of dispersal frequently lack explicit reference to the age or sex of the individuals that disperse. This contrasts with reality where dispersal behavior strongly depends on individuals' state, including age. To study why natal dispersal occurs more commonly than breeding dispersal, we investigate the interplay of 2 categories of explanation: the asset-protection principle (APP) and the "multiplier effect" (ME). The APP states that adults in possession of territories should be more reluctant to disperse. According to the ME, the simple fact of being born tells individuals that the site is of high quality, which may promote philopatry. Our model is set in habitats of spatially varying quality and individuals express different dispersal rates depending on state (life-history stage, sex, and quality of residential habitat). The model considers the accuracy of information about habitat quality, the proportion of good quality habitat, and the magnitude of habitat quality variation. We show that the predictions of the APP hold, but only when the "invisible" asset of likely future prospects in the current habitat is taken into account. Effects of the ME are consistently harder to detect, mainly due to density dependency overriding the benefits of habitat quality. We predict higher natal than breeding dispersal when territorial vacancies are scarce, and more variable breeding than natal dispersal when they are common.