I don't know what it is, but between a random video of a rat dying on youtube that said it was from this stuff, the fact that warfarin has been rat poison for at least 60 years and is really inexpensive, the mention that the dying animal gets thirsty, if I had to guess it is probably warfarin, a blood thinner. It causes whatever eats it to hemorrhage internally. I'm going to guess the rat does not dry up, and that the corpse will be toxic. Just be careful with the stuff and kids. It's what we use around the farm.