The carrying capacity of a fragmented landscape depends on the home-range size of a species

Population models have not considered the problem of home-range settlement when the grain of the landscape is smaller than the home-range size. We present an individual-based model addressing this problem that combines age-structured population dynamics, optimal foraging and habitat selection. During home-range settlement each juvenile tries to maximize her fitness, which depends on the proportion of high-quality habitat in her home range. We assume that home ranges do not overlap, which can happen because the home range is defended as a territory or because individuals avoid areas used by conspecifics. We show that the population supported by the landscape at equilibrium, the carrying capacity of the landscape, decreases with the amount of low-quality habitat cover. However, this decrease is non-linear, the carrying capacity starts to decline only below a critical habitat threshold. Furthermore, when the home-range size is larger than the grain of the landscape, the carrying capacity declines faster when the habitat is fragmented. Therefore species with small home-ranges persist in instances where species with large home-ranges go deterministically extinct. Species with large population growth rates have low critical habitat sizes, and are more resilient to habitat conversion.