Ninken

are essentially dogs that have heightened senses and abilities, and as such, are able to work and be summoned alongside shinobi. Although the dogs belonging to the members of the Inuzuka clan are ninken, the phrase is usually used in reference to the pack of eight ninken summoned by Kakashi Hatake.

Kakashi's ninken have shown the ability to use human language, walk on water, develop combat strategies, and track down targets through their enhanced smell. They are supposed to be quite dangerous in combat, as Kakashi notes in the anime that they can tear their opponents apart on his command. He can summon them separately, as he commonly does so with Pakkun, or all together. He can also summon them for special purposes, like he does with his Summoning: Earth Release: Tracking Fang Technique. With this technique, the dogs can travel through the ground following the scent of their target, emerging when the target is found and holding them in place. They all have a face-shaped design on their backs called — which is the sound made when all the characters in the face are put together. Appropriately enough, children use this design as the face for their scarecrows, which is "kakashi" in Japanese.

In Naruto Shippūden the Movie: The Will of Fire, Ni had two ninken-like beasts at her disposal, that appear to have been mutated through the Chimera Technique.

Inuzuka Clan's Ninken

 * Gaku Inuzuka's ninken (unnamed)
 * Mimi Inuzuka's ninken (unnamed)
 * Gaku Inuzuka's ninken (unnamed)
 * Mimi Inuzuka's ninken (unnamed)
 * Gaku Inuzuka's ninken (unnamed)
 * Mimi Inuzuka's ninken (unnamed)
 * Mimi Inuzuka's ninken (unnamed)

Others

 * Giant Multi-Headed Dog (summoned through Pain's Animal Path)
 * Hōzuki Castle's Ninken
 * Ni's Dogs

Trivia

 * They seem to live longer than regular dogs. Akamaru is at least 25 in the New Era, which is 6 years past the average dog's lifespan.
 * In Naruto: Ultimate Ninja Online, Kakashi's ninken are also summoned by Azure Fang and Midnight Blade.