The reasons why one rabbit’s ears stand up and the other hangs down:

1. Ear mites. If a rabbit's ears stand up and the other droops, it is very likely that one of the ears has ear mites, which makes it uncomfortable.

2. Trauma. If the rabbit's ears are hit by something or hit something sharp, one may stand upright and the other may hang down.

3. It may be normal, but the rabbit is too bored and is playing with itself or listening to some sounds.

Solutions to the rabbit’s ears that stand upright and droop:

1. If there are ear mites in the rabbit’s ears, you need to check them immediately and apply ear drops. Clean the outer ear with oil, then clean the inner ear with ear mite treatment.

2. If there are obvious ulcers, redness, or papule-like lesions on the surface of the rabbit's ear skin, it may be infected, and you should go to the hospital for treatment as soon as possible.

3. If after careful inspection, you find that there is no problem, spend more time with the rabbit and play with it, and it will not behave strangely.