OK, I'll try again. Here's what I'm wondering about. I live in sagebrush country, close to several tracts of public land that is covered in prairie grass and these little cacti, I think they're called prairie *****ly pears. They grow in the grass, in places the cacti grow in bunches close together. They have sharp, stiff little needles a half to one inch long. No person would even think about walking barefoot in this stuff.
I take my dog walking in it every day. He carelessly runs back and forth following his nose. If he finds something to chase he's off at full speed. He's almost never on a leash, same with other dogs I encounter.
Every once in a while he'll sit down and pick at a needle in a paw, sometimes he needs help. But I'm talking about once or twice a year maybe. As I said these cacti grow in the grass, they aren't easy to see. When they're covered in snow they're impossible to see.
So how do dogs avoid them? It seems impossible that their pads are so thick that they don't feel them. Are they?
Edited to say I found my problem. When I tried to post a photo I got the "failed to create a post" message. I'll try in a separate post.
Edited again to say "oh good grief", my OP was censored by Texags. I think these cacti are called Prairie P R I C K L Y pears.