When a dog is afraid, he acts like a deer. Conversely, when a deer feels safe, she acts like a dog.
We can discern in the video the entire scope of behavior. First of all, all animals live by the same bios code, one which is predicated on emotion as a "force" of attraction. Emotion is the universal operating system of animal consciousness. There aren't different operating systems for different species just as there aren't different bios codes for different computers. The Golden is non-plussed by the deer because she fits wholly into this emotional template, she's wholly familiar to the dog because every frame of reference for him is the same. The deer fits into the flow of emotion he's engaged as he trolls the bottom of the stream for rocks. He's not judging that the deer is different from him, from humans, from other dogs. It all fits for him into one flow pattern. We will be misdirected if we judge behavior according to dogs as a separate species, a separate set of information, from deer, at the core level of the animal mind.
All behavior is a function of attraction and this video couldn't make it more obvious. Because the deer can't make direct and active contact with the dog, she then resorts to the zoomies, expressing the force of attraction through the locomotive rhythm; running here and there seemingly at random, but in truth according to a protocol which transfers force to other "objects of resistance" via laminar and turbulent transfers of momentum. When the Golden leaves we see the deer go to the place in the water where he had just been and she sniffs the surface of the water, ingesting by smell his essence and thereby completing the emotional circuitry of attraction. Meanwhile the Golden completes its emotional circuitry by finding an object-of-resistance he can almost ingest but can manage to accelerate (hence a transfer of momentum), a monster rock he fished out of the stream bed and then carries to "ground." Teeth all the worse for wear but mission accomplished. The universal code is satisfied.