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 those of 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 and project regurgitated stomach contents.

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. The smell is so foul that many people who work with alpacas would much rather come into contact with alpaca feces than with alpaca spit. For alpacas, spitting results 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 needs 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 follow.

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.

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 it after he has reached at least two years of age.

It is believed that alpacas generally live for more than 20 years. Conditions and nutrition are better in the USA, Australia, New Zealand and Europe than in South America, so animals live longer and are healthier.