Typically they have dug up and eaten the tasty-smelling tuber. The most daring cow chowed it while the others goggled, and remembered the smell forever after.
I was on one of those investigative rabbitholes and stopped in at various rodent traps. One of the antiques was this contraption with eight holes, in a line, in which rats could stick their heads and be swiftly killed via your basic spring-loaded spinal injury.
Anyway, you could have seven dead or dying rats, heads in, and another rat would clamber over the victims, both the twitching and the finally-still, just to stick its head in the only open hole. The presence of kin corpses and dying nestmates was an insufficient deterrent.