You will be given your dog at the very start of the game. It will start out as a small puppy and wont grow up for about 3 months. Picking up your dog everyday will increase it's heart rating, as will whistling for it to come to you. Don't forget to bring it inside on rainy days, and when Won comes to your farm in Fall, buy the dog ball so you can train your dog. To do well in the Dog Races you will want to get your dog's heart rating up to 10 hearts.