Just in time for holiday cookie season, we’ve discovered that the vanilla flavoring in your baked goods and candy could come from the anal excretions of beavers.

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.