The Animal Path (畜生道, Chikushōdō) grants a Rinnegan user the ability of summoning various animals and creatures to aid it in battle. These creatures appear to be immortal, as they were killed and later summoned again. Worthy of note, summoning creatures through the Animal Path require no blood sacrifice or hand seals. The Animal Path can also summon people; that of which requires hand signs, as in the case of Nagato's Paths and Konan. Tactics wise, the Animal Path's primary role in battle appears to consist on overwhelming multiple opponents with a barrage of summons.
In the case of Nagato, having originally channelled the Animal Path through the corpse of a Fūma clan shinobi and then the corpse of a young woman in life, the creatures summoned appeared to underwent the same modifications as his Paths of Pain, having chakra receivers embedded in their bodies. As they also display the Rinnegan, the creatures serve as extensions of Nagato. During the Fourth Shinobi World War, Nagato used his summons for transport before being rejuvenated to move on his own power.
Buddhists believe that animals inhabit in a different dimension sepparated of the humans not spatially but mentally, an unhappy plane of rebirth which revolves around fear, instinct, survival of the fittest, suffer by those animals that work for humans and above all suffer of ignorance and not having clarity to what is happening to them.