I see only the donkey laughing. How come?

On visit to the zoo a man observed that all the animals were laughing, with the exception of the donkey. Three days later, the man went to the zoo again and noticed only the donkey laughing. The man could not understand this and went to the manager and said, “When I came here three days ago, I found all the animals laughing, except the donkey. Now, three days later, I see only the donkey laughing. How come?”

The manager told the man that three days ago when the rabbit told a joke, the donkey couldn’t understand it and hence didn’t laugh. It is only now that he has understood it and is laughing.