Data and Code for Uncovering the process of sexual segregation early-life individual strategies shape its onset and affect life-history in a large mammal

Sexual segregation is widespread in vertebrates, yet little is known about the mechanisms driving subadults males to leave female groups to join adult males, including life-history impacts. Using longitudinal data from 144 fallow deer males tracked from birth to adulthood, we investigated how early-life behaviour and state influenced segregation processes and outcomes. We identified two key stages: when (and why) a male leaves the female group for the first time and whether (and why) a male revisits the natal area multiple times before completing sexual segregation. Path analysis revealed that heavier and bolder males left earlier, revisited less, and had higher survival rates to adulthood. Males who revisited more often had reduced survival; the surviving ones however recovered their initial body condition disadvantage later. Our study details for the first time the sexual segregation process in a large mammal, enhancing understanding of this key ecological and evolutionary phenomenon in vertebrates.