Children of the Moon

"The true Children of the Moon rarely move in packs, and they are never much in control of themselves."

- Edward on werewolves.

Children of the Moon are creatures similar to the traditional werewolves of myth, not to be confused with shape-shifters.

Physiology
"Full moon, yes. Silver bullets, no—that was just another one of those myths to make humans feel like they had a sporting chance."

- Edward

Children of the Moon change form only at night, and during the fullest phase of the moon. While in their werewolf form, the Children of the Moon lose their human consciousness; they are feral rather than rational. Usually, they run alone, or with one companion of the opposite gender. Children of the Moon cannot breed in their animal form; they can spread their species only by infecting other humans through a bite. Infected humans who have children do not pass their abilities to their offspring.

In their animal form, Children of the Moon have heightened strength and speed that make them both deadly and difficult to kill; contrary to legend, these werewolves cannot be killed with a silver bullet, nor does silver repel them. Their amplified abilities make them capable of destroying a lone vampire while it took several shape-shifters to kill Laurent, a nomad. One advantage the werewolf has in both his/her human and animal forms is immunity to vampire venom, both the transformative properties and the pain-producing properties.

In their changed form, they do not entirely resemble actual wolves: Their forelegs are more powerful than their hind legs, and they still have usable hands with opposable thumbs. In addition, their stance is more upright, making their movement somewhat ape-like, rather than entirely canine.

Because vampires and Children of the Moon share the same food source and because each is an exception to the other's near indestructibility, they are natural enemies. Over time, however, the vampires have hunted the once populous werewolves into near extinction.

History
Not much is known about the Children of the Moon's history. It is known that Caius, one of the Volturi leaders, is terrified of them after he was nearly killed in a fight with one two thousand years ago. Aro and Marcus knew about Caius' encounter, and since werewolves pose a threat to vampires everywhere, they initiated a war against them, resulting in the near extinction of the werewolves in Europe and Asia. It is not known if they are found anywhere else in the world. In Eclipse, it also stated that James hunted one across Siberia though unaware of what it was.

The Volturi refuse to tolerate truces or alliances between werewolves and vampires, under likely punishment of death. This was something that Caius tried to stress when the Volturi put the Cullen family on 'trial' for creating an immortal child. But the werewolves the Cullens had allied with were really shape-shifters in wolf forms, and so the law did not apply.

Quileute shape-shifters
Due to the Volturi's initial assumption that the La Push shape-shifter were Children of the Moon, the two groups probably look very similar in their wolf forms.

While the shape-shifters run in hierarchy and organization, Children of the Moon rarely form packs, and they only run with one companion of the opposite gender. However, in Breaking Dawn, it was commented that true werewolves are disorganized compared to the shape-shifters.

It has been confirmed that they cannot breed in animal form, nor do they pass their abilities to their offspring. Like vampires, they change people into werewolves by biting them, infecting them with their poison. Unlike the legendary version they're based on, they are not vulnerable to silver bullets. Shape-shifters, however, pass their powers to their offspring, but they remain dormant until the carrier comes across a vampire, which will activate his gene, gradually building up his physical stature until he is ready to transform.

Like the shape-shifters, werewolves probably have enhanced strength and speed, rapid healing, and heightened senses. In addition, they are immune to vampire venom in both human and animal incarnations, and their stance is more upright, making their movement somewhat ape-like, rather than entirely canine. However, shape-shifters have a deadly response to vampire venom, while venom alone is not fatal, it can be with addition to serious injuries.