The average life of a dog is between 12-15 years. Their age can be converted into human age. Five dog days are equivalent to one human day. Therefore, a 3-year-old dog is equivalent to a 28-year-old human, a 9-year-old dog has entered the middle age of humans, and a 13-year-old dog is already a 71-year-old senior citizen. Therefore, dogs after the age of 10 are already Senior dogs.