I've had a fair number of donkeys, minis to mammoths, that are terrified of horses. I doubt those would want a stallion near them, especially if they aren't in a full blown "take me now!" heat. We've also bred quite a few jennets that are in heat ONE day and ONE day only. Just like women are different, so are donkeys. Donks usually seem to be in heat fewer days than a mare, for sure tho. I'd say three days is the most. I have a coming 3 year old open jennet out in my pasture that is in heat AGAIN. She comes in heat probably every 18-19 days. My poor jack is so frustrated! But no romancing until April.