Chupacabra - Drawing by Kain White
The first reported attacks occurred in March 1995 in Puerto Rico. In this attack, eight sheep were discovered dead, each with three puncture wounds in the chest area and completely drained of blood. A few months later, in August, an eyewitness, Madelyne Tolentino, reported seeing the creature in the Puerto Rican town of Canóvanas, when as many as 150 farm animals and pets were reportedly killed. In 1975, similar killings in the small town of Moca, were attributed to El Vampiro de Moca (The Vampire of Moca). Initially, it was suspected that the killings were committed by a Satanic cult; later more killings were reported around the island, and many farms reported loss of animal life. Each of the animals were reported to have had their bodies bled dry through a series of small circular incisions.
Physical descriptions of the creature vary. Eyewitness sightings have been claimed as early as 1995 in Puerto Rico, and have since been reported as far north as Maine, and as far south as Chile, and even being spotted outside the Americas in countries like Russia and The Philippines. It is supposedly a heavy creature, the size of a small bear, with a row of spines reaching from the neck to the base of the tail.
The most common description of chupacabras is a reptile-like creature, appearing to have leathery or scaly greenish-gray skin and sharp spines or quills running down its back. This form stands approximately 3 to 4 feet (1 to 1.2 m) high, and stands and hops in a similar fashion to a kangaroo. In at least one sighting, the creature was reported to hop 20 feet (6 m). This variety is said to have a dog or panther-like nose and face, a forked tongue, and large fangs. It is said to hiss and screech when alarmed, as well as leave behind a sulfuric stench. When it screeches, some reports assert that the chupacabras' eyes glow an unusual red which gives the witnesses nausea.
Another description of chupacabras, although not as common, describes a strange breed of wild dog. This form is mostly hairless and has a pronounced spinal ridge, unusually pronounced eye sockets, fangs, and claws. It is claimed that this breed might be an example of a dog-like reptile. Unlike conventional predators, the chupacabra is said to drain all of the animal's blood (and sometimes organs) usually through three holes in the shape of an upside-down triangle or through one or two holes.
Further Reading: http://www.skepdic.com/chupa.html