Did he have diarrhea? That would be my guess. Had the runs and it clumps on their tail. Hair falls out sometimes. Otherwise mom might be over cleaning. Probably diarrhea.
Interesting! That's the normal locations for scours "run off". Have you checked your herd for parasites? Have you seen mom over cleaning?
Moms (especially new moms) have been known to over clean. Because it's a heifer calf id bet that's what's happening.
IF that's what's going on then it will just sort itself out. Just watch for open sore/raw spots. Watch to be sure no one else has anything similar going on.
