Smell information:

There are two "anal glands" near the dog's anus at 4 and 8 o'clock. The main function of the anal glands is to secrete fluid with the dog’s own special odor. In addition to the anal glands, the dog's paws also secrete sweat and other liquids with their own odor. Dogs use each other's scent information to determine their gender, health, estrus, etc.

Tail movements:

The first is the height of the tail. The higher the tail is, the better the mood is; keeping the tail level with the ground means it is in a good mood or is interested in someone. Something shows curiosity; a tail hanging down or even between the legs indicates that the dog is scared or admits to a lower status. (Except for breeds with drooping tails, such as huskies and golden retrievers)

Sound information:

Different calls also represent different messages. For example, the howl of a husky usually informs other dogs, "There is danger/food/I am here", while roaring and low humming respectively mean "Don't mess with me" and "I surrender/ I'm not happy" and so on.

Expression information:

After tens of thousands of years of domestication and companionship by humans, dogs have truly become spirits. They are one of the few animals that can read human expressions. So naturally, because of convergent evolution, dogs themselves will have different expressions. Although it is very basic, such as grinning when angry, closing eyes when happy or relaxed, they all express different emotions of dogs.