Their race were present at Narnia's birth, and existed in it throughout all the ages until the end.
Among their favourite foods is thistles and carrots.
One donkey was mentioned bring present with the other first beasts who captured one of the first humans ever to enter Narnia, who was Andrew Ketterley.
While the Narnians were discussing over what Andrew was exactly, the donkey was described as speaking brightly, and who thought that Andrew might be an ordinary dumb beast who thought he was a Talking beast.
- "I tell you what! Perhaps it's an animal that can't talk but thinks it can."
- ― The first donkey of Narnia (Chapter 11) [src]
When the Narnians decided to keep Andrew as a pet, until Aslan could decide what was to be done with him, they kept him in a cage and fed him various foods. The donkey gave him a bunch of thistles, as that what was what his kind usually ate. Unfortunately, his good intentions were not appreciated by Andrew, who ended up accidentally sitting on them in his small cage.
Donkeys are presumed to have participated in all of the major events and battles of Narnia, but history only mentions two donkeys specifically.
Rabadash the Ridiculous
After Prince Rabadash's shameful attack on Anvard in the kingdom of Archenland, which he did in an attempt to later invade Narnia and capture Queen Susan to force her to be his bride, Aslan changed him into an ordinary dumb donkey as punishment for his actions.
Despite giving him able opportunity to redeem himself, Rabadash continued to act dishonorably in a shameful display of arrogance and pride, threatening everyone alike, until Aslan cursed him.
Because of the affair, the Calormenes called him "Rabadash the Ridiculous" behind his back and after his death.
Puzzle was a friend of Shift the Ape before and during the Calormene Conquest, during the reign of King Tirian. Because Shift was by far the cleverer of the two, he was able to convince the well-meaning Puzzle to participate in the False Aslan Affair by dressing up in a lion-skin and pretending to be Aslan.
Puzzle's conscience was uneasy, despite the Ape's persuasiveness, and he joined Tirian's side midway through the deception. When Aslan ended the Narnian world, Puzzle came in at the stable door to Aslan's Country with all of the other Narnians who loved Aslan. When he finally met the Lion, he was quite afraid and ashamed of himself.
- "The Lion bowed down his head and whispered something to Puzzle at which his long ears went down, but then he said something else at which the ears perked up again. The humans couldn't hear what he had said either time."
- ― The Last Battle (Chapter 16)