One of the most common issues regarding horses, raised with Horsewatch is the plaiting of manes.
We usually ask for people to take photos of the plaits so we can look at them and make a note of when and where.
As for it being marker for theft or not, it is generally agreed amongst the Horsewatches around the country that its not the case although no one can really say 100% because we can't say whether the horses taken had plaits or not.
Over the years we have had lots of reports of plaits, a lot of which are likely wind plaits from the description but it does also include the neat plaits. We have a very very low level of horse thefts in the county which doesn't tally with the plait report numbers.
There are other potential reasons for the plaits but again there are differing opinions. Here are a few links to other organisations/media which may offer some insight/help.
The fact your horse has been plaited does mean that someone has been in your fields so any security measures you can take will all help. There are differing options depending on what your setup is. Unfortunately because there isn't any damage (only plaits) there is only the issue of trespass and that is only the case if there isn't a right of way.
As horse owners, we totally understand how upsetting it is to find neat plaits in your horses mane, whatever the intentions were.