I noticed the other day that my almost five year old female pig, Nicki, has a large area on her neck that is bald. She appears to be healthy otherwise, eating and pooping just fine. I have 3 other piggies, all female, and none have bald areas. Any ideas of what may be causing this. Kathy and the herd of 4 -- Nicki, Simone, Gretchen and Surprise.