Coyotes learn through experience and example from their elders. I get my dogs out in it ASAP in their youth. I am careful about how much and where because if they get covered, it could end up killing them. I have had a couple friends who have lost dogs that way and it is slow. It messes with their immune system. They HAVE to learn to not be crazy in field just because they are chasing a rabbit. My previous dogs and my gsp know to sit and wait for me to come over to pull the ball of spines (or just spines) out using a comb and tweezers. If a trail is covered with small spines, best to avoid it or the offending spot.

We were going out after quail in Arizona near Lake Roosevelt. Tica is 10 months old and it is the first time for her with shotguns so we are trying to take it easy on her. Within 2 min of getting out of the Jeep, she has a big Teddy bear cholla ball stuck to her front leg. She hasn't quite figured out to just wait yet so I run over and pop it off with the comb. She gives this thing a "look" then attacks it! I'm pulling spines out of her mouth for the next 30 min. Good news is that she has NEVER done that again. She is fine now and avoids the visible stuff even if it is dense.

You have a lot of cacti in Canada?