Quite unusual if this is the case. As Isabel said the males have HAVE to mark! My Marlin is guaranteed to water any and all vertical items: stop signs, utility poles, trees, even a person's legs if they stand still in one place too long!

It could be a problem, as if they don't drink enough they may develop crystals / bladder stones.

You can increase his fluid intake by adding some vegetable or chicken broth to his food daily. Not more than 1/4 cup.