Castoreum's the name given to the exudate from the castor sacs of the mature North American Beaver Castor canadensis and the European Beaver, Castor fiber. Within the zoological realm, castoreum's the yellowish secretion of the castor sac in combination with the beaver's urine, used during scent marking of territory. Both male and female beavers possess a pair of castor sacs and a pair of anal glands located in two cavities under the skin between the pelvis and the base of the tail. The castor s… (More on Castoreum)