The first thing I found was an article about Beaver excretion called Castoreum used for Raspberry, Vanilla and Strawberry Flavoring. It's FDA approved and often referenced as a "natural food" flavoring in ingredients lists.
Before you freak out however, you should know that the average consumer is unlikely to be exposed to these Beaver secretions. Mostly because it's hard to milk a Beaver. But you may be thinking that might be the safer option after learning that strawberry flavor is made up of over 50 different chemicals - at least Beaver puss is natural.
So this is whats in Strawberry Flavoring:
Amyl acetate, amyl butyrate, amyl valerate, anethol, anisyl formate, benzyl acetate, benzyl isobutyrate, butyric acid, cinnamyl isobutyrate, cinnamyl valerate, cognac essential oil, diacetyl, dipropyl ketone, ethyl acetate, ethyl amyl ketone, ethyl butyrate, ethyl cinnamate, ethyl heptanoate, ethyl heptylate, ethyl lactate, ethyl methylphenylglycidate, ethyl nitrate, ethyl propionate, ethyl valerate, heliotropin, hydroxyphenyl-2-butanone (10 percent solution in alcohol), a-ionone, isobutyl anthranilate, isobutyl butyrate, lemon essential oil, maltol, 4-methylacetophenone, methyl anthranilate, methyl benzoate, methyl cinnamate, methyl heptine carbonate, methyl naphthyl ketone, methyl salicylate, mint essential oil, neroli essential oil, nerolin, neryl isobutyrate, orris butter, phenethyl alcohol, rose, rum ether, g-undecalactone, vanillin, and solvent.
Some of these chemicals are used in nail varnish remover and are preservatives used in soaps and detergents - oooohhh delicious!
I don't think I have to point out the obvious here - natural is best!
Schlosser, Erica. Fast Food Nation; The Dark Side of the All-American Meal, page 126, Houghten Mifflin Company