Alpacas have a life expectancy of about 20 years. Females reach breeding age at about 18-24 months old. Males are not potent (ready to breed) until they're at least 24 months old. When in good health, females will breed their entire lives (with a break every few years for recovery). When born, alpacas weight about 15-18 pounds. They are nursed from their mothers until they are about 6 months old. Twins are extremely rare in alpacas.
Alpacas are herbivores, which eat plants. They graze on grass, weeds, trees, and shrubbery. They have 3 stomachs, which allows them to absorb 50% more nutrition from their food than sheep do. Because they are able to absorb so much nutrition from their food, they do not need a high nutrition diet like other grazing, domesticated animals do.
Alpacas have been domesticated for about 6,000 years. The Moche people of Peru have been using alpacas in their art for thousands of years. There are no known wild alpacas; all breeds are domesticated.
Alpacas are too small to be used as pack animals (like their relatives, the llama and camel). They are primarily bred for their soft fiber (fur) and their meat. The Andean inhabitants used to consider alpaca meat a rare delicacy.
Alpacas are social herd animals. They live in large groups, usually led by an alpha male. These large groups have been used as “guard llamas” for herds of sheep. They make a loud, high-pitched noise when an intruder (wold, coyote, etc) is near. The alpacas will attack using their front feet and spit at the intruder.
The closest answer provided under this question is four million alpacas. However, the real answer is probably closer to three and a half million alpacas in the Andean highlands. The Andean highlands, for those not in the know, are some of the highest peaks in the Andes mountains range - which runs down the coast of western South America. Most of the highlands are contained within Ecuador.
Alpacas are animals that have been domesticated - IE become used to interacting with humans without hurting them. The best way to describe how they look is like a llama half the size of a normal llama. They’re adorable, and their fur is often used to create soft wool yarn for sweaters, scarves, etc. to be made from.