Summary is a bit inaccurate, leading to uninformed comments and questions on this thread. From the article,
The researchers found that the rats chew the bark of the poisonous tree and lick themselves to store their poisonous spit in specially adapted hairs.
They do not eat the plants. They chew it. This is the same way people chew certain herbs and then apply it to wounds to numb the pain. They don't eat those plants - if they did they'd be in poor health indeed.
In every hierarchy the cream rises until it sours. -- Dr. Laurence J. Peter