Seed defences shift granivore satiation across seed densities

Predator satiation is typically viewed as a function of seed abundance, yet plants also vary widely in seed defences that shape handling costs. Whether such traits modify satiation dynamics remains unclear, despite the role that predator satiation plays in the evolution and ecological consequences of masting.

We experimentally manipulated seed density and spatial distribution using two oak species that differ in mechanical defence and tracked removal and post‐dispersal fate by scatterhoarding rodents. We also measured the force required to pierce acorn shells to quantify differences in mechanical resistance between species.

In the well‐defended species ( Quercus rubra ), key components of seed fate shifted with increasing density: removal and consumption declined and dispersal distance shortened. In the less defended species ( Quercus robur ), these responses showed little change across densities. These contrasting patterns coincided with a nearly fourfold difference in acorn shell mechanical resistance between species.

Synthesis . Our results show that predator satiation is not determined by seed abundance alone: mechanical seed defences can shift the density at which consumers become satiated, shaping density‐dependent seed predation and dispersal. Thus, the effectiveness of masting depends on both seed abundance and seed traits.