Once you've begun clicker training animals, you'll find that they are very keen indeed to continue the clicker game! They become keen students and this can present a hazardous situation. In my case, I have three donkeys loose together.
Several things can happen:
1. they might rush up to you, overjoyed to see if you want to train/play with them
2. they might crowd you
3. they might mug you or your pockets for treats
4. or they might pin their ears at one another, or kick or bite and you might be in the way
This is what happened to me today. Dorica got so mad at the other two for crowding her space that she whirled and kicked and yours truly was in the line of fire. I didn't get hurt, luckily but one can never take safety for granted.
Then Deenah rushed Dorrie and kicked her in the gut full on - I heard the smack. The fault was mine, I was in a bit of a hurry, it was late in the day and I thought I could get a bit of clicker work "in" without being organized. WRONG!
Don't do this ever. Remember that you are always training, any time you are with your animals - they don't understand that "now we're having a lesson, now we're not" - they are learning all the time. Before you do any training, be organized, use halters or separate animals and work one on one.
As soon as my donkeys hear even a quiet "click" sound that I might make, even if some are a ways away, up go the ears and they appear, anxious to play. I have to be ready for that and not take safety for granted.