Mike get a pair of BRT's lol. We have talked before about this, if you have the willingness to train to at least CD level with them.
But yes Irish Wolfhounds would keep coyotes away too. I love them too, but 7-8 yrs is a heartache I just can't go to.
TEll me what else, are you looking to keep the bigger dog(s) outside in kennel type arrangement?
I am trying to think of something that is good with Yorkies, easily trained, and okay indoors or out.
Many guard breeds could be good, but the same criteria would apply as to the BRT;s.
What about a pair of border collies? BUt sheesh they might have too much prey drive for the Yorkies; not sure about that.
I can tell you a Tibetan Mastiff would scare not only coyotes away but wolves and even cougars. Not sure where you live, but I just heard from my camping friends, cougars have now been sighted in near North Ontario.
