Rockruff is a quadrupedal, canine Pokémon. It is primarily light brown with a darker brown muzzle, paws, and ear tips. It has large blue eyes, button ears, a short muzzle with a triangular pink nose, and a short tuft of fur on each cheek. Around its neck is a ruff of grayish-white fur stubbed with dark brown pebbles. The dark brown markings on its paws extend to a thin point on each wrist and ankle. It has a grayish-white tail that curls tightly over its back and is covered in fluffy fur.

Rockruff has an excellent sense of smell and will never forget an odor after smelling it once. There are tales of it reuniting with its Trainer after becoming lost by following the faintest traces of scent. It has lived with humans since ancient times. Rockruff is often recommended as a good Pokémon for beginner Trainers due to its friendly nature and ability to bond with Trainers easily. However, Rockruff is said to be a challenging Pokémon to raise, to the point where some Trainers abandon it due to being unable to handle it. This Pokémon is very sociable and will greet others by rubbing them with the rocks around its neck. As it ages, Rockruff becomes wilder and more independent. Once it is close to evolving, it will begin to howl when the sun goes down. It has been said to leave its Trainer's side and return once it has evolved. Despite becoming more vicious as it matures over time, Rockruff never forgets its master's kindness. Wild Rockruff travels in packs until it evolves. A persistent Pokémon, it will keep going until it outlasts foes that are even more powerful. Rockruff intimidates opponents by using the rocks on its neck to hit the ground. As mentioned in the anime, Rockruff trains itself by running around. It attacks foes the moment they flinch. It has been known to fight with Growlithe over territory.

Rockruff can evolve into Midday Form, Midnight Form, or Dusk Form .

(Source: Bulbapedia)