The skin when they are in human form is “burning hot” (NM12). Bella feels this first when she believes Jake has a fever on the way home from the trip to see the movie. “Whoa, Jake—you’re burning up!” (NM9) but it is common enough for his body to be consistently at this temperature. Werewolves are clearly the polar opposites of the vampires, with their icy-cold touch and marble-like skin. Perhaps their physiological make up reflects the tension between them.
“We run a little warmer than the normal people. About one-oh-eight, one-oh-nine. I never get cold anymore. I could stand like this” —he gestured to his bare torso— “in a snowstorm and it wouldn’t bother me. The flakes would turn to rain where I stood.” (NM15) Stephenie Meyer says this is one of the unique features of her werewolves.
They are also able to heal very quickly physically. Injuries don’t last very long at all.
“He’ll be perfect by sundown.”
“By sundown?” I looked at the line on Paul’s arm. Odd, but it looked weeks old.
“Wolf thing,” Jacob whispered.(NM14) We see this again when Jake cuts his hand so badly that it should need stitches and then moments later it has healed: “It should have taken days to scab over and then weeks to fade into the shiny pink scar that marked his skin now.” (EC9)
The actual transformation between human and werewolf is described in most detail in "New Moon’. Certainly the initial transformation is not an easy one, as Jake explains his symptoms to Bella: “Everything,” he whispered. “Every part of me hurts.” (NM9) Initially, I thought that this must be physical pain that Jake was experiencing, but Stephenie explained that this wasn’t actually the case. “The transformation into the wolf form is not a painful process, only disorienting and mentally uncomfortable.” (PC11) It is mental pain that Jake is referring to, from the fact he has realised that he is both a monster and the implications this has in his relationship with Bella.
The transformation itself can happen at any time, and isn’t dependent upon a full moon. In young werewolves cases, they can change involuntarily because of lack of self-control:
“What would happen…if you got too mad?” I whispered.
“I’d turn into a wolf,” he whispered. (NM13)
The effects of this sort of transformation is shown in the relationship between Sam and Emily and the disfiguring injuries she has suffered. (NM15, PC11)
Transformation is a sudden process and is described through a series of violent words: “burst”, “exploded”, “vibrating violently”, “ripping”, “blasted” (NM14). It is so sudden “that if I’d blinked, I’d have missed the entire transformation” (NM14) Initial transformations seem to be triggered by anger, and Jake explains that his own conversion to becoming a werewolf was staved off by his happiness with Bella: “I was like a time bomb. You know what set me off? I got back from that movie and Billy said I looked weird. That was all, but I just snapped. And then I—I exploded. I almost ripped his face off—my own father!” (NM15). Sam Uley’s transformation also supports this, as it “took him two weeks to calm down enough to change back.” (EC5)
Jacob seems to find phasing between wolf and human form easier than most. “Even Sam couldn’t have phased on the fly like that. He saw Paul losing it, and it took him, what, half a second to attack? The boy’s got a gift.” (NM14) He explains later to Bella that this may be due to his ancestry: “It takes some practice to phase back and forth but it’s easier for me… because Ephraim Black was my father’s grandfather, and Quil Ateara was my mother’s grandfather.” (NM15). Because his lineage is so very strongly linked with the last pack, it seems to be easier for him than most
Werewolves are only created when there are neighbouring vampires, so that the Quileute land is always protected. Jacob explains that:
“There’s no exact age…it just builds and builds and then suddenly—” (NM15)
It seems to occur around the point where the boy becomes a mature man, and is certainly accompanied by a sudden growth spurt.
Their sense of pack-identity is strong. So much so that they are capable of hearing “…thoughts—each other’s anyway—no matter how far away from each other we are. It really helps when we hunt, but it’s a big pain otherwise. It’s embarrassing—having no secrets like that.” (NM13) Even in wolf form, they retain full control of their human minds. “They are still themselves–not at all the feral, mindless werewolves of other mythologies.” (PC11) This means that all actions are knowing actions, although it is entirely possible for a werewolf to lose his temper and for him to be out of control as both a human and a wolf. Jacob shows his human side in wolf form on the run up to the fight with Victoria, when he pulls a face with “his tongue lolled out the side in a wolfy grin” to make Bella giggle. “Jacob’s grin widened over his sharp teeth.” (EC18)
Werewolves were believed to be only male until the transformation of Leah Clearwater, which surprised everyone, even though “she’s a direct descendant, all right.” (EC19). The issue of imprinting is also critical as this is how the werewolf finds the one person they are destined to be with forever: “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.” (EC8)
Their sense of smell has adjusted to help them identify their one enemy. “Vampire,” he spit out…“I can smell it! Dammit!” (NM16) It is not clear whether it is heightened in other circumstances, but they certainly know vampires from a distance and find the smell sickly sweet and repellent.
Like vampires, they are also very strong; Bella breaks her hand punching Jake: “It was broken, I could feel it.” (EC15)
Finally, someone has the wolf inside them for life: “What I am was born into me” (EC4), and whilst they are still mostly wolvish, they “can’t… grow up,” (EC5) and stop aging. Jacob explains that this is only until they “stop phasing for a solid length of time [then] we age again.” (EC5)