We have three DSH sisters that we adopted from the animal shelter as kittens
back in 1996. We were told that the trio had been found in a utility shed;
no report on the whereabouts of their mother. They were just a few weeks old
when we got them, and had just been copy protected. They're wonderful little
girls, and we love them dearly, and they're pretty tolerant of us most of
the time.

Recently, they've all adopted a strange behavior, one after the other. A
couple times of day, and minimum, one of them will lie down somewhere comfy
and start trying to nurse on herself. Not off a teat, but usually on a
foreleg, or often a shoulder. They each have always enjoyed being scritched
along the spine, just above the tail; now doing this triggers very energetic
efforts of this sort.

The first one that started doing it, Purpy, will do the same thing to my
hand if I put it in the way of her forelegs. Pinky, the most aggressive of
the three girls, has actually worn away little bald spots on each foreleg,
and is rapidly thinning out a spot on each shoulder.

Has anybody seemed behavior like this from their cat companions? I will be
finitely grateful for any advice or suggestions.