Alpacas are social herd animals and should always be kept with others of their kind, or, at the very least, with other herd animals. They are gentle, elegant, inquisitive, intelligent and observant. As they are a prey animal, rather than a predator, they are cautious and will understandably be nervous if they feel threatened. They like their own space and don’t appreciate an unfamiliar alpaca (or human) getting too close, especially from behind. They will warn the intruder away by making sharp, noisy inhalations, putting back their ears, twisting their heads and necks backwards toward the perceived threat, screaming, threatening to spit, or by spitting, or by kicking. Some alpacas kick, some don’t, but due to the soft pads on their feet, their kicks are not as dangerous as hoofed animals. Not all alpacas spit, but all are capable. "Spit" is somewhat euphemistic; while occasionally the contents of the projectile are only air and a little saliva, the alpaca will often bring up regurgitated stomach contents and fire away.

Spitting is mostly reserved for other alpacas, not for humans, but sometimes the human can get in the line of fire. However, if the alpaca is extremely displeased at a human, that person may well become covered in smelly, horrible green goo. Many people who work with alpacas would much rather come into contact with alpaca feces than with alpaca spit - the smell is that foul. Spitting isn't any fun for the alpaca, either; when they spit, most animals get what is called "sour mouth." Sour mouth is characterized by a loose-hanging lower lip and a gaping mouth. This is caused by the stomach acids and unpleasant taste of the contents as they pass out of the mouth. Some alpacas will spit when looked at, others will never spit - their personalities are all so individualized that there isn't a hard and fast rule about "alpacas will always/never" in terms of social behavior.

Alpacas don’t like their heads being touched. Once they know their owners, and feel confident around them, they will probably allow their backs and necks to be touched, but they won’t appreciate being grabbed, especially by boisterous children. This is probably because when alpacas are caught up for medical or otherwise unpleasant procedures, people generally grab at their necks and hold them by the neck and head. Once socialized well, most alpacas will tolerate being stroked or petted anywhere on their bodies, although many do not like their feet and lower legs handled. If an owner need to catch an alpaca, the neck offers a good handle – and holding the neck firmly between the arms is the best way to restrain the animal.

To help alpacas control their internal parasites they have a communal dung pile, which they do not graze. Generally, males have much tidier dung piles than females who tend to stand in a line and all go at once! One female will approach the dung pile and begin to urinate and/or defecate, and the rest of the herd will often decide, "Hey - that looks like a good idea!"

Because of their preference to use a dung pile, some alpacas have been successfully house-trained! Difficult though it may be to conceive of having a large animal such as a full-grown alpaca around the household, many owners so love their animals that they wish to be in their presence as much as possible. If acclimated to dogs and cats, alpacas can accept them as members of the herd, and will interact with nearly all species which do not pose a threat, from birds and butterflies to horses and humans.

Sheep baa, cows moo and alpacas hum. Different animals have different voices, but basically it is a "mmm" sound. Hums are often comfort noises, letting the other alpacas know they are present and content. However, humming can take on many inflections and meanings, from a high-pitched, almost desperate, squealing, "MMMM!" or frantic question, "mmMMM!" when a mother is separated from her offspring (called a "cria,") to a questioning "Mmm?" when they are curious. Alpacas make other sounds as well as humming. When danger is present they sound an alarm call, a high-pitched, shrieking whinny of sorts. Some breeds are known to make a sound similar to a "Wark" noise when excited, and they stand proud with their tails sticking out and their ears in a very alert position. Strange dogs – and even cats – can trigger this reaction. To signal friendly and/or submissive behavior, alpacas "cluck," a sound possibly generated by suction on the soft palate, or possibly somehow in the nasal cavity. This is often accompanied by a flipping up of the tail over the back.

When males fight they also scream, a warbling bird-like cry, presumably intended to terrify the other combatant. Fighting is to determine dominance, and therefore the right to mate the females in the herd, and it is triggered by testosterone. This is why males are often kept in separate paddocks – when two dominant males get together war breaks out! When males must be pastured together, it is wise to trim down their "fighting teeth," large fang-like teeth whose name explains their function.

A male in the act of mating, or hoping for a chance to mate, will “orgle.” This orgling will help to put the female in the mood, and it is believed that it also helps her to ovulate after the act of mating – very necessary for a pregnancy to take place! The females have no estrus cycle, per se - they are "induced ovulators," which means that the act of mating and the presence of semen causes them to ovulate. Occasionally, females will conceive after just one breeding (which can last anywhere from 5 minutes to well over an hour; the males are "dribble ejaculators,") but occasionally do have troubles conceiving. Artificial insemination is prohibitively expensive and there are complications with the process in camelid species.

A female is usually ready to mate for the first time at a year of age; however, a female alpaca is not fully mature (physically and mentally) until she reaches approximately 16-18 months, and it is not advised to breed a female before that time. The male's penis is attached to the inside of his body, and will generally not detach until at least two years of age. The penis is a very long, thin, prehensile organ that is, oddly enough, perfectly designed for the task of finding the vaginal opening despite a fluffy tail, penetrating the hymen (if present,) navigating the vaginal canal and entering the cervical opening, where deposit of the semen occurs.

Pregnancies last between eleven and eleven and a half months and the young are called crias. After a female gives birth, she is generally receptive to breeding again after approximately 15 days. Crias may be weaned through human intervention at approximately 6 months of age and 60 pounds. However, many breeders feel that allowing the female to decide when to wean her offspring is the proper way to have this process occur.

Alpacas generally live for more than 20 years – we think! Conditions and nutrition are better in the USA, Australia, New Zealand and Europe than in South America, so animals live longer and are healthier. One of the oldest alpacas in New Zealand (fondly known as Vomiting Violet) died at the end of 2005 at the ripe old age of 29.