Do Pubescent Seeds Encourage Secondary Dispersal by Dung Beetles

In tropical forests, primary dispersal by birds and mammals is a disproportionately important form of seed dispersal. Dung beetles are secondary seed dispersers attracted to mammal dung. When they bury dung of fruit-eating mammals they move seeds that are not too large, to new, possibly safer or better microclimates away from conspecifics, and potentially increasing rates of germination. We observed three species of dung beetles (Oxysternon conspicillatum, Canthon angustatus, and Can- thidium sp.), all treating the large (2 cm long) Spondias mombin seeds defecated by a brown-headed spider monkey (Ateles fusciceps fusciceps) as though the seeds were dung, even though S. mombin is approximately 1.6 times longer than the upper size limit of seeds normally included in either O. conspicillatum’s dung logs or Canthon angustatus’s dung balls. The seed’s soft hairs covering its surface hold a thin layer of dung and possibly "trick" the dung beetles into treating them as a dung ball, moving them away from other conspecific seeds. The dung beetle loses in this situation because they cannot eat the seed. At the genus level large, mammal-dispersed (endozoochorous), seeds are disproportionately pubescent. This may indicate that secondary dispersal by dung beetles can exert some selection pressure on mammal dispersed seeds.