Habitat dimensionality and mean search distances of top predators: Implications for ecosystem structure

The foraging success of top predators may be influenced by the shapes of their habitats. We show here that when a two-dimensional habitat is restricted to a narrow strip or a three-dimensional system to a thin plate, then searching predators must travel further between prey items. This result holds when the width of the strip or thickness of the plate is narrower than twice the perception range of the predator, and when prey are not particularly abundant. If, as would be expected, travel time and energy expenditure increase with distance travelled, restricting the dimensionality of a habitat will decrease the net energy gain of a predator per prey consumed. This in turn may affect the size of a predator population that a given habitat can support, and ultimately determine whether the top predator species is viable in the habitat. This mechanism provides one explanation for observed relationships between the lengths of food chains and habitat dimensionality.