Werewolf/Twilight

When they smell a vampire, their gene is triggered, their physique builds until they shift for the first time. Descended from ancient native spirit warriors. The warriors and chiefs could leave their bodies and wander as wolf-spirits, communicate with animals, and hear each other's thoughts. All descendants of the great warrior-chief.
* Sam Uley: Sam is the wolf that scares Laurent away from Bella Swan in New Moon, and is described as enormous, jet black, as tall as a horse, but thicker and much more muscular, with dagger-like incisors, and a grisly snarl like a prolonged crack of thunder. His wolf form was even mistaken for a "bear".
* Jacob Black: As a wolf, Jacob is bigger than Sam Uley, and has deep rusty-brown fur. When the wolves rescue Bella from Laurent, she realizes that the russet wolf has Jacob's black-brown eyes.
* Paul Lahote: Paul is smaller than Sam and Jacob, and has dark silver fur.
* Jared Cameron: Jared is the same size as Paul, with brown fur, darker over the face.
* Quil Ateara V: Quil is described as being chocolate-brown, lighter over the face.
* Embry Call: Embry is slim and sleek, with pale gray, black-spotted fur.
* Leah Clearwater: As the only female member of the pack, Leah is smaller than the males, with light gray fur.
* Seth Clearwater: Seth is tall and gangly with oversized paws, and has sand-colored fur.
* Brady Fuller: Brady has dark, ashy brown fur that almost appears gray.
* Collin Littlesea: Collin has reddish brown fur, with a darker color on his legs, face and tail.
* The appearances of the seven other wolves that join the pack at the end of Breaking Dawn are not specified.
Each wolf's distinctive color and characteristics correlates with each wolf's true self. Quil Ateara V and Sam Uley joke with one another that Sam's black fur is due to his "black heart", while Quil's chocolate-brown fur reflects how "sweet" he is. No real explanation of this phenomenon is given; none, perhaps, should be sought for - variability is the one fundamental of living beings. Active shape-shifters cut their hair short, as the length of their hair correlates with the length of their fur. Leah cut her hair to chin-length.
Monstrously sized wolves. In human form they are between 6'0" and 7'0" tall. Grow to become bigger, more muscular, and harder in look and substance, deepened voice and larger appetite. As humans they have short hair, hard-muscled bodies, and unusual height. Members of a pack have synchronized movements, and can be mistaken for biological siblings. Their gene for changing is triggered when smelling a vampire for the first time, to protect their own kind, can happen at any age, generally occurs when coming of age and gives a sudden growth spurt for about two months, intense mood swings, and higher body temp. The turn is sudden and violent, shredding their clothes, the first turn is triggered by anger. They can change back by calming and concentrating. Those who inherit the gene from both sides of their family can shift faster. It usually takes practice to learn to shift back and forth. They can turn anytime, and is involuntary for those that have not yet learned control. Often turn from anger. Even as humans, faster and greater endurance, swift and sleek as a deer. Can run at 100 mph, a fast wolf can outrun an average vampire, and a fast vampire can outrun an average wolf, usually equal in speed. Can communicate with each other telepathically and so can hunt well as a group. Highly developed reflexes.
=== Strength ===
In their human forms, they possess enhanced strength superior to that of regular humans. However, they are supernaturally stronger when in their wolf forms: their strength is incredible and nearly equivalent to that of a vampire. A full pack can easily overpower and kill any vampire, and, as seen in Eclipse, is a formidable force when dealing with an army of newborns. Bella notes that Jake handles her "too roughly", and that, when he hugs her, it's so "crushing" that it nearly suffocates her. She also states to Jacob that "normal humans can't throw motorcycles around the way you can" when he remarks how more human he is compared to vampires. He doesn't seem as aware of his strength as the vampires, but this could be due to the newness of his phasing. In Breaking Dawn, Jacob snidely comments on how Rosalie would react if he threw her into a wall and took this notion even further when he kicked her across the room when she lost control of her thirst over Bella's blood during Renesmee's birth—even breaking the door in the process despite her indestructibility which he compares to "kicking concrete".
Strong and ferocious.
=== Physiology ===
Shape-shifters have a body temperature of (42°C) 108.9°F. Bella feels it first at the movie theater in New Moon, when she believes Jacob has got a fever. Vampires' temperatures are lower than humans'; it is possible that the wolves' and vampires' physiological differences reflect the tension between the two species.
This high temperature allows the shape-shifters to withstand very cold weather and makes it difficult for them to become overheated. It also makes it very difficult for vampires to harm them in combat, due to vampires being extremely sensitive to high temperatures. After Bella becomes a vampire, she describes Jacob's skin as like "touching an open fire" and "unbearable to the touch."
The shapeshifters can heal and regenerate very fast and completely. While not immortal if they choose to quit phasing, these capabilities allow them to continue fighting even after serious injury. In some cases, however, this accelerated healing can be detrimental. After Jacob was crushed by a newborn in Eclipse, his skeleton healed before Carlisle could set his bones, forcing Carlisle to break a number of them to induce proper healing. In Breaking Dawn, Jacob comments that even a bullet through his temple might not be enough to kill him. However, this healing factor is not completely reliable and can be neutralized if vampire venom is inserted into the shapeshifter's system. While venom alone isn't generally enough to kill a healthy shape-shifter, it can be fatal in combination with other injuries.
The actual transformation between human and wolf is described in the greatest detail in New Moon. Certainly the initial transformation is not easy, and is very disconcerting and confusing. If shape-shifters don't phase for long periods of time, they slowly begin to age until their aging reaches normal human speed. However, they still retain their phasing abilities, even in their old age, as shown with Taha Aki and Ephraim Black.
While their skin is much more durable than that of a human being (to the degree that the bones in Bella's hand are broken when she punches Jacob in the face), it is not granite hard like a vampire's. In their wolf form, their fangs and claws are strong enough to penetrate a vampire's skin. Bella witnesses this for herself during the climatic battle in Eclipse when she sees Seth easily biting through Riley's skin.
The wolves bear an animal scent that makes them unappetizing to vampires, making it easier for vampires to resist the temptation caused by their blood. It is possible that their scent is less revolting to vampire hybrids due to their half-human sides. They also have sharp canine teeth in their human forms.
=== Senses ===
The senses of shapeshifters rival those of vampires. Like vampires, they can see, hear and smell things from miles away. Of special note, vampires have a distinctive scent that shape-shifters are aware of in both their human and wolf forms, finding their scent uncomfortable to the point of pain - a sickly sweet smell that burns. Each vampire has their own personal scent, which is easily distinguishable to shape-shifters. They can pick up this scent from a good distance or any item a vampire has touched.
However, some shape-shifters can get used to the smell of the vampires, such as Seth Clearwater and Jacob Black in Breaking Dawn. They both spent time with the Cullen family, and feel more comfortable than before around vampires.
Shapeshifters' eyes are extremely sharp and can see very far. Jared is known to have the best sight in the pack. Their sense of sight is known to be ten times better than the average human, twice as good as the average bird of prey's. It is unknown if shape-shifters can see into the invisible spectrum of light, like vampires. Even in their human form, a wolf can easily recognize a vampire. They see much more than the characteristic paleness, eye color, and beauty. To wolves, a vampire appears reflective and angular, almost like moving crystal.
They all have excellent hearing even in their human forms, although not the same extent as their wolf forms. In Breaking Dawn, Jacob was able to hear Quil playing with Claire at First Beach from his bedroom. Seth Clearwater is known to have the best hearing in the pack.
== Pack behavior ==
: Main article: Pack structure
In their wolf forms, shape-shifters show the general behavior of their titular animals, though they retain their human intelligence, memories and character, up to and including showing their human eyes. Pack members are also telepathically linked with each other, enhancing their coordination during hunts and fights but allowing little or no privacy at any time. The Alphas of two different packs are able to communicate telepathically, and can control what thoughts they share, while the subordinates of different packs don't show this ability.
The dominant male, the Alpha, can force the other pack members to obey his orders against their will. So can the Beta, though he can't command his own Alpha. Even if it's implied, it is unknown whether this characteristic is also extended down the pack hierarchy.
Alpha status is related to lineage, with Sam being the exception due to Jacob, the born Alpha, having no interest in leading the pack. However, should a genetical Alpha be unavailable, it is possible for a pack to select a new Alpha from, possibly, its ranks. Though possible, it is not known whether a lower-ranking pack member can challenge the Alpha for status. Jacob never uses his voice to impose his will on his pack mates, even if he has a stronger power than Sam.
In Breaking Dawn, it is found out that Bella Swan is able to mentally shield a whole pack of shapeshifters by focusing solely on its Alpha, with the protection cascading down through the ranks.
== Usage of the term ==
In the context of the Twilight Saga, the term "shapeshifter" is used as a title applied only to the direct descendants of Taha Aki who have actually phased - that is the members of the Uley family, the Black family, and the Ateara family.
Being descendants and fathers of shapeshifters, Harry Clearwater, Joshua Uley, Quil Ateara III and Billy Black have the genetic makeup and the potential for phasing into wolves. However, they weren't exposed to vampires while growing up, so the gene was never triggered.
== Genetics ==
While treating Jacob, Carlisle takes a blood sample and runs some tests on it. He discovers that they have 24 pairs of chromosomes, one more than a human and one less than a vampire, but the same number as vampire hybrids. The exact nature of the extra chromosome is unknown, but it may carry the genes needed for the shape-shifting abilities of the bearer. The hypothesis is that it is somehow passed down only in Y-chromosome carrying sperm, which would explain why almost all shapeshifters are male, while the occasional extra chromosome being passed down in an X-chromosome carrying sperm could be the basis of Leah Clearwater's appearance. Or, alternatively, it may be that it is passed regularly by both sexes (both males and females) and that testosterone may be needed as a co-inducer for the shape-shifting complex together with whatever external trigger needed for phasing - Leah having a high concentration of testosterone in her bloodstream.
Pack symbol tattoo. 
== Children of the Moon vs. Shapeshifters ==
During the confrontation with the Volturi, Edward reveals that the werewolves of La Push are actually shape-shifters and not Children of the Moon. The Children of the Moon go along with what people usually associate with werewolves: they only transform during a full moon, and create other werewolves by infecting a human with a venomous bite, much like a vampire, rather than genetically like the Quileutes. Though they are not harmed by silver bullets. According to Edward: "There aren't very many of them left. Caius has had them hunted into near extinction."
The issue of imprinting is also critical as it is how the shape-shifters find their soulmates. According to Jacob Black, "It's not like love at first sight, really. It's more like... gravity moves. When you see her, suddenly it's not the earth holding you here anymore. She does. And nothing matters more than her." Once shape-shifters have imprinted, they will feel the need to constantly be in their soulmate's presence and to unconditionally give them whatever they want or need. Should the imprintee be an infant, the shape-shifter will act as an older brother; romantic feelings will not develop until she comes of age. Imprinting works on both humans and hybrids. In Jacob's case, his hatred for vampires disappeared when he imprinted on a hybrid. It is shape-shifter law that no wolf may harm the imprintee of a fellow pack member, as this will lead to destructive in-pack fighting.
Imprint.
== The Quileute packs ==
In Breaking Dawn, Seth is informed that Bella and Edward have returned home, and that Bella has contracted a rare disease. Jacob soon finds out that she is pregnant with Edward's child, instead. Sam and the others fear the harm the child could bring and plan to destroy the Cullens including Bella and her hybrid spawn. Jacob and Seth leave Sam's pack and form their own, in defense of the Cullens. They are soon joined by Seth's sister, Leah, who wanted to get away from Sam and protect her brother. After the birth of Renesmee, Jacob imprints on her and the shapeshifters' feud with the Cullens is put to an end as it is strictly forbidden for any shape-shifter to harm the object of another shape-shifter's imprinting.
Carnivorous. Endangered. Turn into feral wolf-like creatures on the night of a full moon. Never much in control of themselves. Involuntary wolf-beast transformation.
The Children of the Moon, also known as werewolves, are human beings that at night, at the fullest phase of the moon, transform into fearsome feral wolf-like creatures. Werewolves, unlike shape-shifters, have the strength and power to kill a vampire single-handedly. Their strength coupled with their inability to control the shift into their wolf forms makes them extremely dangerous and resulted in many vampires fearing them. This fear lead to the Volturi nearly eradicating all werewolves from Europe and Asia.
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. The greatest 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. Unlike the Quileute shape-shifters, Children of the Moon lose all their consciousness and rationality while in their animal form. This gives vampires one advantage in battle, as they retain their focus and fighting skill.
Vampires have hunted them nearly to extinction.
==Wolf Form==
Upright stance, ape-like movements, forelegs more powerful than hind legs, usable hands, opposable thumbs.
Rarely form packs, run alone or with one companion of the opposite gender. Disorganized.
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.
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