Beaver butts secrete a goo called castoreum, which the animals use to mark their territory. The U.S. Food and Drug Administration lists castoreum as a “generally regarded as safe” additive, and manufacturers have been using it extensively in perfumes and foods for at least 80 years, according to a 2007 study in the International Journal of Toxicology.
“I lift up the animal’s tail,” said Joanne Crawford, a wildlife ecologist at Southern Illinois University, “and I’m like, ‘Get down there, and stick your nose near its bum.’”
“People think I’m nuts,” she added. “I tell them, ‘Oh, but it’s beavers; it smells really good.’”
Castoreum is a chemical compound that mostly comes from a beaver’s castor sacs, which are located between the pelvis and the base of the tail. Because of its close proximity to the anal glands, castoreum is often a combination of castor gland secretions, anal gland secretions, and urine.