Blood has been a symbol of life since very ancient times. The blood in our veins has always been iconic of our continuing life. To lose too much blood is to lose consciousness, breath, and eventually, our very lives. If a person or animal is already dead and is cut open, blood does not flow. Only the living have blood that flows. Blood has been used throughout the ages as a ceremonial sacrifice. In pagan times our forefathers worshipped their gods with blood sacrifice. And today, indeed, we are not so different. Even in modern times, in our churches, there are those taking communion or the Eucharist, and drinking of the wine that symbolizes Christ's blood.
It seems appropriate, then, that this creature who is an antithesis of both death and life should gain his strength from feeding from the life's blood of humans. For the vampire, the drinking of blood is its life, its sustenance, and the single thing that makes it identifiable all around the world, regardless of the culture in which you were raised or the language you speak.
As the ages progressed and new modern technology and medicine became available to the masses, the exact nature of the vampire's need for blood changed. In many literary instances it was linked to anemia, and blood loss. In Bram Stoker's Dracula, Van Helsing prescribed a blood transfusion for Lucy, in an attempt to divest her of the vampire blood in her body.
Blood is what animates the vampire, what gives him his life. Without it he can dry up into a husk, much like a starved human. Many theories have been tested in fiction as to why it is so. In Anne Rice's Vampire Chronicles, the entire vampire race is infested with a demon/spirit that makes them what they are, and the demon needs blood in order to retain his hold on their collective bodies. Thus, the need to feed on blood, particularly when the vampire is a fledgling.
A vampire must drink blood in order to survive. And so, with our advancing understanding of how animal and human evolution works, vampire novels and stories in the late nineteenth century began to describe the vampire as having protruding or elongated canine teeth. This made it easier for the vampire to puncture the skin of the neck and the jugular vein while feeding. Up until that time, however, vampires were not thought to have fangs at all. But it is a fact that races of animals (we humans as mammals are included in this) evolve physically to make their tasks easier to perform. And so it is with the vampire.
As cinematic prowess increased and the movie industry was able to do more with special effects, a new vampiric ability evolved. In movies today it is common to see the vampire with retractable canine fangs. This allows him to circulate with humans more easily; with the fangs retracted, he is more easily perceived as human. In Forever Knight, the character Nick's fangs only protrude when his dark, vampiric nature is unleashed.
In European and Slavic history, fingernails were thought to be one of the tell-tale signs that a corpse was a vampire. Vampires were thought to lose their old nails and grow new ones upon their entry to the vampiric world. An exhumed body that lacked nails or had grown new ones was summarily staked, and very often burned or reburied with garlic to seal the corpse within the ground.
In modern literature, two major vampire novels have mentioned fingernails specifically. In Dracula, Jonathan Harker notices that Dracula's "nails were long and fine, and cut to a sharp point." When Dracula later opened a wound on his chest for Mina Murray to drink his blood, he did so with these sharp, pointed nails. In Anne Rice's Vampire Chronicles, Louis and Lestat both mention the glassy appearance of their fingernails, so different from that of humans. Many times it is something that they take care to hide.
The histories of both European and Slavic vampire hunts also show hair growth as a sign of vampirism, although this sign was generally not found unless the corpse also displayed many other traits thought to be associated with a vampire.
Anne Rice does discuss hair in her Vampire Chronicles, although she is one of the few. Her vampires are cursed with the same length of hair that they had when they died and were made into vampires. Regardless of how often they cut it, it will always grow back.
The term Dhampir refers to the offspring of a vampire and a human mate, traditionally a male vampire mating with a human female. This offspring was normally male. The dhampir was thought to have special qualities. He could sense where vampires hid themselves from the world, and therefore he had the ability to be a superb vampire hunter. These qualities would be passed down genetically to his offspring, and it was thought to last many generations.
As well, the terms incubus and succubus refer to vampires who perform a sexual attack upon their intended victims, and it was likely these types of vampires who produced offspring. However, references to exactly how (!) this was accomplished is very scarce.
A vampire's sense of vision is thought to be very acute. This is largely due to the fact that they are a nocturnal creature, and therefore must be able to adapt to their environment. It also explains why sunlight is thought to be so painful to their eye. Their eyesight has often been attributed to a residue from their ability to change into bats (see Shape Changing).
Hearing is also heightened in a vampire body. This allows them to hear mortals from a great distance (far greater than human ears could pick up) and also to discern when another vampire draws near. This is evident in Forever Knight; Nick can hear over great distances, and this allows him to capture the criminals he chases. Their acute sense of hearing may also be attributed to their nocturnal nature; as night hunters, the ability to hunt quietly and hear well would be invaluable.
Although there was a small link between shape-changing and vampires for hundreds of years, it was not until Dracula that the true connection was made. In the novel, Stoker described Dracula as able to change into a rat, a bat, or the very mist itself.
Vampire bats became by far the most common of these shapes a vampire could command at will. This could be because vampire bats, by their nature, are closely related to the vampire itself. They are nocturnal, and feed exclusively off the blood of various mammals and other vertebrates. They have very sharp teeth which they use to pierce the victim's skin, and then they lap up the blood as it flows. It has also been known as an emerging problem; it is a proficient carrier of rabies (not unlike the definition of Nosferatu, which itself mean plague-carrier).
The ability to transform at will into mist has brought many advantages to the vampire, allowing him to escape vampire hunters and other dangers quickly. In addition, mist (in some cases) has allowed the vampire to move great distances at one time.
Historically, vampire skin was dark instead of the alabaster skin we see today in film. Paul Barber, author of Vampires, Burial and Death, suggests that this is becuase suspected "vampires" were actually corpses decomposing in their graves. Skin naturally turns darker and sloughs off the bone as the body decomposes. This may account for many reports in medieval Europe of vampires "growing new skin".
Today, vampire skin is by nature very white and smooth. This is likely due to the fact that these creatures are nocturnal, and never get to see the sun. Their skin therefore gets bleached over time. Also, the vampire is an undead creature, and unless he has recently fed, there is a lack of colour-giving blood in his body.
In The Vampire Chronicles, Anne Rice describes the vampire skin as nearly transparent when the vampire is starved for blood. After feeding, they attain a healthier, more human skin tone, but this is a temporary change. Lestat mentions on several occasions having to powder his skin to pass for human.
The vampire came by its supernatural strength through modern film and literature. Vampires, historically, were not know for their great strength; they normally attacked only "weaker" victims, such as children or the elderly. They never attacked a group of people for fear of being overcome. However, the modern view of vampires have allowed them a certain arrogance, knowing that no mere mortal could overpower them. Many of the personality traits that we have come to so adore in the vampire today are a result of this arrogance, knowing that they are truly immortal but for a few weaknesses.