sauron wrote on Aug 6, 2012, 15:47:

Blue wrote on Aug 6, 2012, 14:41:

sauron wrote on Aug 6, 2012, 13:39:
This behavior is male territoriality (try saying that after 2 pints of beer!), so I'm assuming he's entire?

In a younger dog, getting him fixed might solve the problem, but in older males like the Gunnar-man it probably won't help - too late for it to make a significant difference.

He is, as they like to say "intact." I've seen it argued both ways whether this contributes to the tendency to mark, but most seem to agree that it does, which also seems the intuitive answer. But even those who feel that neutering helps with marking seem to agree that by the time he's all grown up this horse is out of the barn, so while we may be tempted to castrate him as a punishment, it doesn't sound like it will solve our issue.

Yes, neutering wouldn't help at all at his age.

If it were me, I'd use judicious use of the word 'No' while showing him the 'incident' so he knows the context. I also mentioned before you can combine this with a gentle smack with a rolled-up sheet of paper/newspaper. The latter is just to make noise, for reinforcement of the message.

Hopefully, he gets it eventually. Good luck!