My friends yorkie started doing this out of nowhere. She noticed her doing it one night that her anal glands emptied while she was humping her toy. She immediately stopped and hasn't done it since. I think she was trying to releive her anal glands. She talked to her vet and the vet says it was only a dominance thing and had nothing to do with the glands. But it seems so coincidental that she stopped as soon as she was able to empty the glands. Though the vet did tell her to make her stop and not let her keep on, because she could hurt her back, if she continued. Luckily I have never had that problem with any of my dogs, I pray that my good luck continues.
__________________  Dena,  Ava  Obie |