Answer:
In the Amazon rainforest, the agouti (a small rodent) and the brazil nut tree are very dependent on each other. The brazil nut tree drops its pods when they ripen, but they would not split open if it were not for the agouti's sharp teeth - the only forest animal which can split the tough pods. The agouti benefits by eating the brazil nuts, but like squirrels, agoutis hide and bury surplus nuts - and many of these take root, thus replenishing stocks of brazil nut trees.
