Bad case of ear mites that was never taken care of would do it. Some type of head trauma could do it. An ear infection that wasn't taken care of could do it. They aren't normally deaf from birth if they aren't BEW. Of course being older could do it too. How old is your male? Have you checked his ears good? What made you determine that he might be deaf?
He's 18 months old. I know a dog with an ear infection or ear mites would shake their head a lot, wouldn't an alpaca do the same thing? I haven't seen him do that...but I'll check his ears.
If he's not facing me or the other alpacas when I call them he doesn't react at all. I have to walk out to him until he sees me out of the corner of his eye or wait until he turns around and hold up the grain scoop and THEN he comes running over.
Interesting. I would guess that something happened. Maybe he had oxygen deprivation or something at birth. He may or may not do a lot of shaking of the head with mites or infection.