The Brazil nut tree encloses its seeds in a hard indehiscent pod that falls intact. Agoutis have the incisors and the persistence to open it. Having done so, they eat some seeds immediately and scatter-hoard the rest in shallow single caches across the forest floor.
Radio-tracking and camera studies in Panama and Amazonia show these caches are repeatedly stolen and re-buried by other agoutis, sometimes moving a seed dozens of times and hundreds of metres from the parent tree. This serial re-caching, rather than a single burial, does much of the dispersal work. Seeds left in an unopened pod on the forest floor almost never germinate successfully.
The relationship is often summarised too neatly. Agoutis are the principal disperser of Brazil nut and several other large-seeded species, but the Brazil nut work concerns Amazonian Dasyprocta species rather than this Central American one, other scatter-hoarders including acouchis and squirrels contribute, and the mix varies by site. Brazil nut regeneration also depends on pollination by large-bodied bees, which is a separate constraint.