Male mice injected with estradiol deposit that chemical in female genitalia

Hormone Behavior has a special issue devoted to chemosignals. I thought this particular line was interesting;

Quote: systemic injection of tritiated estradiol (3H-E2) into a male mouse or bat has been shown to produce significant levels of radioactivity in the reproductive tissues and brain of cohabiting female conspecifics.

http://www.ncbi.nlm.nih.gov/pubmed/25125222

So inject a male mouse with a particular molecule and the exact same molecule winds up in the genitalia of the female mouse.