Nest defensibility decreases home-range size in central place foragers

Lameris, Thomas K.; Brown, Joel S.; Kleyheeg, Erik; Jansen, Patrick A.; Langevelde, Frank van


Variation in the home-range size of nesting animals is thought to be driven by nutritional requirements, food availability, and predation risk of the animals during foraging. Only few studies have considered that the risk of nest predation may also affect home-range size because nests become more difficult to defend as animals move further away. We used a theoretical model to explore the combined effects of nest defensibility, nest predation risk, and food availability on foraging distance from the nest, and hence home-range size. In our model, foragers adjust the foraging distance around the central place such that the required amount of food is collected within the available time with the lowest predation risk for the nest. We found that foraging distance decreased with food availability and the risk of nest predation during absence, but also with nest defensibility. When food was abundant, both nest predation risk and defensibility hardly influenced foraging distance. When food was scarce, animals able to deter predators foraged close-by, whereas animals less able to deter predators foraged further away. Likewise, animals that were themselves vulnerable to predation stayed closer to their nest if the nest provided safety, as is typical for central place foragers. This study is the first to assess the importance of nest defense and nest predation risk for foraging distance of central place foragers and provides a better understanding of the drivers of home-range size.