A viral video currently doing the rounds shows a large herd of sheep mysteriously walking round and round in a large circle. The unusual phenomenon was captured at a farm in the Inner Mongolia region of Northern China and had reportedly been going on for at least 10 days, according to the Chinese newspaper People's Daily.
The media in China said that the behavior, shown in the black-and-white CCTV footage (video below), had no clear explanation, leading internet users to develop their own juicy theories. In between ideas of alien invasions and doomsday omens, many were speculating that the behavior may have been caused by the bacteria Listeria monocytogenes.
When farm animals eat food infected with this germ they can develop a disease called listeriosis, which can affect their nervous systems. The infection can take root in just one side of the brain stem, resulting in one side of the animals’ faces becoming paralyzed and their heads tilting at an angle. This titled head causes them to walk in a circle, hence the disease is sometimes nicknamed "circling disease".
While this is a pretty reasonable guess, some experts suspect something other than listeriosis is going on in this video.
"They'd show a variety of circling and other neurological conditions and they'd get quite sick – some would die," Andrew Fisher, a professor of cattle and sheep production medicine at the University of Melbourne, told ABC News.
"The way it usually manifests is not in half the flock – it's sort of between 1 and 10 percent might be affected."
Instead, others are hypothesizing as to whether the animals in the video are showing signs of stereotypic behavior. This is when an animal exhibits a repetitive behavior pattern with no obvious goal or function, often in response to stress, frustration, or boredom. Perhaps the most obvious example of this is a caged animal at a zoo pacing up and down its enclosure.
"It looks like the sheep are in the pen for long periods, and this might lead to stereotypic behavior, with the repeated circling due to frustration about being in the pen and limited [as to where they can go]. This is not good. Then the other sheep join as they are flock animals and bond or join their friends," Matt Bell, a professor and director of the Department of Agriculture at Hartpury University in England, told Newsweek.
With this in mind, it’s also likely the sheep are practicing their well-known tendency to follow the herd. Recent research has shown that this behavior is surprisingly democratic and much more than just blindly following the leader. But regardless of its complexities, it does appear sheep rely on the self-organizing “hive mind” of the flock to dictate some of their movements.
So, if a significant block of the herd starts to wander around in circles due to frustration, it makes it likely that the rest will follow suit. Whether or not this can explain this circling behavior going on for over a week is another question. However, it’s safe to say that nothing too "X-filesy" is going on in Inner Mongolia at the moment, and it's more likely to just be some very bored sheep.