Lampreys are parasites that look like slimy eels with mouths that are ringed with several layers of jagged teeth. In some areas, like the Great Lakes of the United States, they've become an invasive pest that kills local trout and other valuable fish.
So Michigan State researchers decided to come up with a foolproof lamprey repellant. After discarding several ideas, they hit upon the idea that nothing is scarier than smelling your own dead. So they whipped up a fluid that they describe as a "semiochemical mixture produced by the putrefying carcasses of sea lampreys." Yes, they liquified rotting sea lampreys and poured the goo into a bathtub full of perfectly innocent lampreys.
Above, you can see their reaction to the scent of their own species' rotting death. It's what you would do too, if you smelled the odor of a thousand zombies.
And here's an underwater view of the same panic response.
(Spotted on New Scientist)
Photo by Kurt Stepnitz