Kevin The Herbivore.

[AChimp]

Hmm... I heard somewhere that they once created a virus that would attack the Y chromosome in rabbits, thus crippling their ability to breed within a few generations; a kind of population control.

But then they realized how easy it would be to turn it into a weapon, and they voluntarily destroyed their work. Not sure if it's true, though... it sounds more like a biology/genetics urban legend.