This morning I was listening to a radio discussion about the multi-modal sensing used by dogs. It reminded me of one of our dogs from many years ago (oh boy, geezer reminiscing).

Koa was a pure bred German Shepherd. One of his favorite things were rocks; any rock (larger than a tennis ball) was fine with him. He would pile them up and lay by them, play with them and carry them around in his mouth.

The interesting part of Koa's rock love was his ability to find a rock you picked up and threw. He could find a rock that was thrown into tall weeds and trees, among many other rocks, as far as you could possibly throw it. Sometimes it would take him ten minutes to find that exact rock. He always brought it back to you and dropped it at your feet for another "toss". If you chose to throw a different rock, he would find that one as well. If another person threw a rock he would go find that one and bring it back to that person, too.

One day, I accidentally threw a rock into the river that flows by our property. Much to my surprise Koa swam out into the river and dove under multiple times until he found that exact rock. Underwater rock fetching became a favorite activity.

I assume then that Koa used several senses to find the rocks including:

Sight (seeing what the rock looked like and the direction it was thrown)
Sound (hearing the approximate direction and location where the rock landed)
Smell (smelling the "tosser" of the rock)
Rock sensor (well, no, but it did seem like that sense existed too)

Good dogs constantly amaze me.

I can understand how the dog can find a rock thrown into the forest due to the residual scent from your hand, or the dog's saliva from a previous retrieve.

I have also seen dogs do retrieves under water. In air, I can grasp how their nose can follow the scent molecules to the object. I CANNOT grasp how they do that in water, but they clearly have that capability.

I definitely want to thank the first human that tossed a bit of meat to the inquisitive wolf that approached his fire.

I currently have a German shepherd who retrieves whatever I throw including sticks, by scent. He does this for rocks underwater by submerging his nose. When a stick gets caught in a tree, he also finds it by scent and after realizing it up, he tries to jump and get it. His eyesight is not too great anymore, but his nose is phenomenal. He puts our other 4 German shepherds to shame in that respect, but each of our dogs has their own superpower. With 5 German shepherds, we sleep well at night, unless they hear something... I love this breed, but 5 large dogs in the house is a handful...

RAH, mixed sexes or all male or female?

The black-and-tans, and one silver are males. We bred the darker male with our silver female and kept a silver male and silver female. Momma dog had 13 pups! One of those pups had a moment of fame.

https://www.fox9.com/news/dog-wakes-up-owner-to-alert-her-to-husbands-heart-attack-saving-his-life

Both females are now spayed. Little girl survived a broken neck when she apparently ran head first into something that did not move. She is the one that is airborne in this pic. She is fearless.

Dogs amaze me. I had a Springer Spaniel that @ 30 pounds could flush a pheasant, and jump up about shoulder high in the air and grab the bird. Come back to the ground, put her paw on it, roll it around so she could grab it from the back so she didn't get spurred and bring it back alive, no puncture marks in the skin, and no broken bones on the bird. This same one would also dive under the water to bring back whatever you threw, or even if it was a waterlogged bird that sank.

They can also tell within about 5-10 feet of what direction a bird is moving, they don't back trail for very long at all. Just think about that for a minute, the scent discrimination that they have is amazing.