We are pretty sure our Bulldog runs on sight only - a rabbit crosses the road in front of us - dog hits the bush after the rabbit - hear that Bulldog start barking way deep in bush - then she comes back out, to where we think the rabbit started from - THEN she starts sniffing where that rabbit went - so all the rabbit has to do is hit the bush on the run, make a sharp turn and the Bulldog goes right past - chasing "something" - but then she comes back to check the scent trail - in mean time, the rabbit is probably 1/2 mile away telling his buddies about that stupid Bulldog back there! In Winter time, the dog has to about sniff every track on the snow - people, dogs, cats, etc. - has her nose down in the snow - not sure what she is sniffing for? We have seen her take on Momma Black Bears with cubs and antler-less whitetail deer on the road - she is NOT a "push-over"!