Relatively little is known about the cause of seed loss in the soil once initial dispersal has taken place. The vast majority of dispersed seeds fail to emerge as seedlings. Seeds buried in soil tend to have a more or less exponential decay (Roberts & Feast, 1973). Some may be eaten; others may be attacked by pathogens. Another possible fate is germination at depths that are too great to permit emergence. A large fraction simply may lose viability in the course of time and die of old age. We will examine each of these possibilities in turn.

Post-dispersal predation

Post-dispersal seed predators are typically granivorous mammals (e.g. rodents), birds (e.g. finches) and insects (e.g. beetles and ants), but the taxonomic range of seed-eating organisms is wide and includes slugs (Godnan, 1983), earwigs (Lott et al., 1995), fish (Kubitzki & Ziburski, 1994) and crabs (O'Dowd & Lake, 1991). Seed predation can be regarded as a specialized form of herbivory. Because it impinges directly on the capacity of plants to regenerate, it can play a key role in population dynamics. The proportion of seeds eaten varies greatly between species, locations and years, but it is often extremely high. For example, capuchin monkeys were recorded as eating 99.6% of the seeds of the wind-dispersed forest tree Cariniana micrantha at a site in Amazonia (Peres, 1991). In a Costa Rican tree, Ocotea endresiana, rodents ate 99.7% of the dispersed seeds within 12 months (Wenny, 2000b).