This is one of the topics least thought of by many owners, Philly has many great parks and I see a lot of people at them, but it seems no one really knows that much about it.
But it is the ONE thing that any hunting breed dog thinking about almost every minute of the day.
Love or hate him, Caesar Milan is 100% right about the order that dogs use to decide an appropriate plan of action. They use SMELL, SIGHT then sound. And that is often the order of the sensitivity or selectivity of their senses.
Where as humans use SIGHT, then maybe sound and smell usually well behind most other senses.
There is much debate about how this evolutionary trait occurred and there are exceptions but they are far and few between. Looking at the domestic dogs ancestors and working your way forward makes as much as anything.
Evolution from the wolf was relatively recent, so it’s a good idea to start there. Wolves are a pack animal and a scavenger. To survive they must have a tight pack unit and hunt regularly. They were often found to be living in woods, where direct sight lines can be difficult and short winter days (little light) meant that they needed a super sensitive nose to pick up tracks. While their eyesight is exceptional at night time, not all animals are nocturnal, so hunting in all environments in all types of weather and light conditions meant that the sense of smell was one thing they strongly relied upon.
Like wolf cubs, dog puppies are born blind and bond with their mother through the sense of smell, not sight. If a puppy gets separated from its mother, it doesn’t stand much of a chance if she can’t recognise it among her other puppies, or cant track where it has wandered or been taken to. For this she uses the sense of smell to define each puppy.
You may think that the dogs ancestral reliance of smell is enough to understand why it is so important, but it still plays a very big part of a domestic dogs life if you will let it.
Testing of the area of a dogs brain that deals with smells coupled with the massively more complex and large area evolved for pig dog smell ability in another blog.