The acorn is the nut of the diverse oak tree family usually containing a single seed enclosed in a tough, leathery shell and borne in a cup-shaped cupule. They may take from 6 to 24 months to maturebr/br/Acorns are too heavy for wind dispersal so depend on biological seed dispersal agents such as various rodents and birds to collect, consume and disperse the seed. Acorns are attractive to animals because of their comparitive large size and high nutritional value; however the leaves and acorns of the oak tree are poisonous to cattle, horses, sheep, and goats in large amounts due to the toxin tannic acid.