I talk to them alot when we are out for a hike. Not really a conversation, but I try to make some noise regularly---it's good bear protection. If a bear hears us coming, he is much more likely to keep his presence hidden!

On the sled, I speak only to give commands and the occasional bit of praise. If you talk too much to a working sled dog, they stop listening--which can be a problem when you need a response to a command!