https://www.yahoo.com/news/aliens-cold-hundreds-sheep-walk-185445715.html "Hundreds of sheep walked in circles for days in China with no explanation, a video shows. The mysterious sight has drawn many questions and speculations. The sheep in the northern Chinese region of Inner Mongolia walked in an endless circle for over 10 days, the People’s Daily reported along with a video on Wednesday, Nov. 16."
I saw someone say it's a semi-common behavior when sheep get bored. They get put into a small pen where they can't roam, so they just start walking. A circle is the most efficient way to do that. Even if it's not common, ants do the same thing when they accidentally start following one another and lose the real trail. Then they just follow one another in a massive spiral until they either die or something, like rain, comes along to disrupt the trail.
